CHEHALIS RIVER BASIN STUDIES
INVENTORY AND EVALUATION
Final Report
June 15, 2012
LEWIS COUNTY CONSERVATION DISTRICT:
Dr. Frank Reckendorf, G. Fluvial Geomorphologist
Dean Renner, P.E. Stream Mechanics Engineer
Robert Amrine, District Manager
Kelly Verd, Special Projects Coordinator
Nikki Wilson, CREP/GIS Specialists
And
Mark Stevens, P.E. SW Washington Area Engineer,
Douglas Fenwick, Engineering Tech., Clark Conservation District
Funded by:
TABLE OF CONTENTS
ACRONYMS
INTRODUCTION
Purpose
Objectives
Methodologies
SETTING
Location
Sub-basins
Population
Potential Flooded Areas
Physiography and Geology
Local Topography
Land Use
Climate
Surface Water
Annual and Mean Monthly
Peak Flows
Historic Flooding
Water Bodies
Estuary
Drainage
Sedimentation
Upland Erosion Landslides
Accelerated Streambank Erosion
Ground Water
Water Quality
Fluvial Geomorphology
Wetland Habitat
8
10
10
10
11
12
12
12
12
13
13
17
18
18
18
18
18
21
24
26
28
29
31
35
35
37
41
43
Aquatic Habitat
Land Resource
Soils
Land Capability
Upland Forestry Vegetation
Clearcutting
Rate of Harvesting
Riparian Vegetation
Upland Forest Riparian
Riparian Management Zones
(RMZs) and Wetland Management
Zones (WMZs)
Shade Requirements to Maintain
Water Temperature
Cultural Resources
WATER AND RELATED LAND RESOURCES PROBLEMS
Flooding
Stage and Frequency at
Representative Gage
Bankfull Discharge
Previous Studies
Existing Flood Control Works
Potential Flood Reduction Solutions
Non-Structural
Instream Measures
Missing Data
Accelerated Soil Erosion Reduction
Upland
Landslides and Debris Flows
Accelerated Streambank Erosion
Sedimentation Impacts
Estuary
Fluvial Geomorphology Needs
47
52
52
53
56
56
57
57
58
58
58
58
59
59
60
61
62
66
69
69
72
72
73
73
74
75
76
79
79
Drainage
Ground Water
Water Quality
Aquatic Habitat
Wetlands
CONCLUSION
SCOPE OF FUTURE WORK
REFERENCES
ABSTRACTS and MAPS
81
81
81
85
87
87
90
91
TABLES
1.
2a.
2b.
2c.
3.
4.
5.
6a.
6b.
7a.
7b.
8.
9a. &
9b.
10.
11.
12.
13a.
13b.
Chehalis Basin Watershed-County Land Areas
Sub-areas in Chehalis Basin as shown in SCS River
Basin Report
Watershed Area by HUC and WRIA
Floodwater Hazard Classes for Chehalis Basin by
Watershed
Annual Streamflow Data for Chehalis Basin
Monthly Streamflow Data for the Chehalis Basin
Daily Streamflow Data for Chehalis Basin
Peak Discharge for Selected Frequencies
Chehalis Basin Discontinued USGS Stream Gages
Dates of Historic Flood Events from 1930 – 2010
Dates of Historic Flood Events from 1930 – 2010
Peak Discharges and Corresponding Flood
Frequency
Percent Riparian Cover
Water Bodies: Named Lakes and Dams and
Reservoirs
Sediment Yield for Sub-basins
Timing of Salmon Fresh-water Life Phases
Erosion Los between 2006 and 2009 by Site
Potential Food Reduction Projects & Policies
Potential Flood Reduction Studies and
Methodologies
FIGURES
1.
2a.
2b.
3a.
3b.
3c.
3d.
4.
5.
6a.
6b.
6c.
6d.
6e.
6f.
7a.
7b.
7c.
8a.
8b.
9.
10.
11.
Overview of Chehalis Basin
Chehalis Basin WRIA 23 Watersheds
Chehalis Basin WRIA 22 Watersheds
Maximum Extent and Drainage Routes of the Vashon
Glacier
Chehalis River Profile- Lewis County Washington
Chehalis/Skookumchuck River Profile-Lewis County
Washington
Chehalis/Newaukum River Profile-Lewis County
Washington
Stage Discharge Watershed for Satsop River near
Satsop, WA gage
Stage Discharge for Satsop River near Satsop gage
1938 Photo Centralia Area
2011 Photo Centralia Area
1938 Photo Porter Area
2011 Photo Porter Area
1938 Photo Stearns Creek Basin
2011 Photo Stearns Creek Basin
Generalized Conceptual Model of Groundwater Flow in
the Centralia-Chehalis Lowland
Water Quality Monitoring Sites throughout the Chehalis
Basin
Core Summer Salmonid Temperature Conditions in the
Chehalis River Basin
The Key to the Rosgen Stream Classification System
Channel Evolution Model
Stream Planform Montgomery and Buffington
Pattern of Soils and Parent Material in the ReedChehalis Map Unit
Riparian Assessment for Newaukum River, Lewis
12.
13.
14.
15.
16.
17.
18.
19.
20.
County
Upper Chehalis and South Fork Chehalis River Erosion
Sites determined by comparing 2006 to 2009 aerial
photos
Side by Side Aerial Photos 2006 and 2009 Site 1
Side by Side Aerial Photos 2006 and 2009 Site 2
Side by Side Aerial Photos 2006 and 2009 Site 3
Side by Side Aerial Photos 2006 and 2009 Site 4
Side by Side Aerial Photos 2006 and 2009 Site 5
Side by Side Aerial Photos 2006 and 2009 Site 6
Side by Side Aerial Photos 2006 and 2009 Site 7
Side by Side Aerial Photos 2006 and 2009 Site 8
ACRONYMS
BMP’s
BP
CAO
CBP
CFS
CMER
COE
CREP
CRSP
CWA
DNR
DOE
EDT
EIS
EPA
ESA
FEMA
FFR
GIS
GMA
HUC
IACWD
LCCD
LHZ
LiDAR
LWD
MCD
MLR
MSL
NAP
NFIP
NRCS
NWIS
OHWM
RCW
RCYBP
RMZ
Best Management Practices
Before Present
Critical Areas Ordinance
Chehalis Basin Partnership
Cubic Feet per Second
Cooperative Monitoring and Evaluation Research
Committee
United States Army Corps of Engineers
Conservation Reserve Enhancement Program
Chehalis River Surge Plain
Clean Water Act
Washington State Department of Natural Resources
Department of Ecology State of Washington
Ecosystem Diagnosis and Treatment
Environmental Impact Statement
United States Environmental Protection Agency
Endangered Species Act
Federal Emergency Management Agency
Forest and Fish Rules
Geographical Information Systems
Growth Management Act
Hydrologic Unit Code
Interagency Advisory Committee on Water Data
Lewis County Conservation District
Landslide Hazard Zonation
Light Distance and Ranging
Large Woody Debris
Mason Conservation District
Multi-Linear Regression
Meters above Sea Level
Natural Area Preserve
National Flood Insurance Program
Natural Resources Conservation Service
National Water Information System
Ordinary High Water Mark
Revised Code of Washington
Radio Carbon Years Before Present
Riparian Management Zone
RLIP
RM
RMAP
RPW
SCS
SMA
TMDL
TNW
USDA
USFWS
USGS
WAC
WAU
WDFW
WARSSS
WMZ
WRIA
WSCC
Regional Landform Identification Project
River Mile
Road Maintenance and Abandonment Plan
Relatively Permanent Water
Soil Conservation Service
Shoreline Management Act
Total Maximum Daily Load
Traditional Navigable Water
United States Department of Agriculture
United States Fish and Wildlife Service
United States Geological Survey
Washington Administrative Code
Washington Administrative Unit
Washington Department of Fish and Wildlife
Watershed Assessment of River Stability and Sediment
Supply
Wetland Management Zone
Water Resource Inventory Area
Washington State Conservation Commission
INTRODUCTION
Purpose
The purpose of this study was to collect, inventory and prepare a report on
existing technical studies and similar reports for the Chehalis River Basin in
order to identify study needs for evaluating flood reduction alternatives that
could be implemented in the Chehalis Basin. The report was written in the
style of a river basin report that is traditionally written by the Natural
Resources Conservation Service (NRCS). As such, it looks at all of the soil
and water resources that would need to be considered in any future work on
flood reduction in the Chehalis Basin.
The study was funded by a grant from NRCS to the Washington State
Conservation Commission (WSCC). The WSCC provided matching funds
and designated the Lewis County Conservation District (LCCD) as the lead
agency to do the study and prepare the report on behalf of the six county
conservation districts in the Chehalis Basin.
Objectives
The objectives of the study were laid out in a plan of work and an agreement
was signed between the NRCS and the WSCC. The objectives were as
follows:
1. Complete an inventory and evaluation of existing technical reports
and studies completed by Federal, State, County, and Tribal
agencies.
2. Prepare a report summarizing the pertinent studies and reports.
3. Determine the technical adequacy of each inventoried report to
reflect a comprehensive basin study.
4. Identify additional study needs necessary to encompass all
potential flood reduction alternatives.
5. Develop a scope of work for additional study needs that have been
identified within the Chehalis Basin.
10
Methodology
This study was undertaken to inventory all studies and other types of
documents that related to the Chehalis Basin. It is commonly thought that
the Chehalis Basin has been studied intensely but there was no
comprehensive database that existed of what had been completed. Using lists
put together by several sources, the LCCD sought out documents on the
internet, at various libraries, the United States Army Corp of Engineers
(COE), other government agencies, and any other available source.
A total of 768 titles of documents were identified. The majority of the
documents were found but a few were unable to be located. They were left
on the list as they do relate to the Chehalis Basin and maybe found in the
future. There are a few documents that are not specific to the Chehalis Basin
but contain information that would be useful. Although this is meant to be a
comprehensive list, it is possible there are some documents that we were
unaware of.
A unique identifying number was created for each document. An Access
database was created and abstracts were written for each document. Each
was assigned to one of the following categories: Bibliographies, EIS’s,
Fisheries and Habitat, Flood Reduction, Flood Studies, General, Geology
and Geotech, Grays Harbor Navigation, Groundwater, Historical and Misc.,
Water Quality, Water Resources, or Wildlife. The documents were reviewed
for overall usefulness to the goal of flood reduction. The documents were
ranked as excellent, good, fair, or not relevant. They were also ranked for
relevance of study goals, relevance of analysis, relevance of information,
and relevance of findings. In the final report, the documents are sorted by
category, then overall usefulness, and then by the ID number.
SubBasin maps were created for each report that showed which area of the
watershed the study covered. The maps are based on the 12 digit Hydrologic
Unit Codes (HUC’s). This is a method of dividing up the subwatersheds
developed by the United States Geologic Survey. In a few instances, the 10
digit HUC was used to identify the watershed. The maps are included
separately from the Access database.
11
SETTING
Location
The Chehalis Basin, with the exception of the Columbia River, is the largest
watershed in Washington. It is bounded on the east by the Cascade
Mountains and the Deschutes River Basin, on the north by Puget Sound and
the Olympic Mountains, on the south by the Willapa Hills and the Cowlitz
River Basin, and on the west by the Pacific Ocean. Elevations vary from sea
level at Grays Harbor to 5,054 feet (Capitol Peak) in the Olympic
Mountains. The Chehalis Basin drains 2,766 square miles (Tetra Tech /KCM
and Triangle Associates, 2004).
Sub-basins
The Chehalis River flows through the Cascade, Puget Lowlands and Coast
Range Ecoregions (Figure 1). The outlet is Grays Harbor near Aberdeen.
The basin can be divided into sub-basins designed by the Washington
Department of Natural Resources (DNR) as the Upper Chehalis Basin
(WRIA 23) and Lower Chehalis Basin (WRIA 22). The Chehalis Basin area
by counties is shown in Table 1 (Anchor QEA,LLC, 2012). A different
system used to characterize sub-basins is shown in Table 2. This system is
the Conservation Needs Inventory used by the Soil Conservation Service
(SCS) in their 1972 river basin report (USDA,Soil Conservation Service
(SCS), 1972). Also shown in Table 2, is the 12 digit HUC number for each
sub-watershed.
The Chehalis Basin lies mostly in Lewis, Thurston, Mason and Grays
Harbor Counties as shown in Figure 1, but also drains portions of Pacific,
Cowlitz, Wahkiakum, and Jefferson Counties. Figures 2a and 2b show how
the sub-basins are separated by HUC’s.
Population
The total population of the basin is approximately 140,000 people. The
major population centers are Chehalis (~6,000), Centralia (~12,000), in
Lewis County in the upper basin, and Aberdeen (~16,000) and Hoquiam
(~9,700) in Grays Harbor County in the lower basin. The communities of
12
Chehalis and Centralia have experienced significant flood problems over the
years. The major population centers in Thurston County that lie within the
basin are Tenino and the community of Rochester. The average rate of
population growth in WRIA 23 from 2000 to 2025 is projected to be 52%
(Tetra Tech /KCM and Triangle Associates, 2004). There are many rural
communities in the basin such as Adna, Dody, Dryad, Boistfort, Curtis,
Napavine, Pe Ell, Tenino, and Bucoda in WRIA 23, and Elma, Montesano,
Hoquiam, Aberdeen, Westport, and Ocean Shores in WRIA 22. Many of
these have experienced significant flood damage.
Potential Flooded Areas
It is difficult to exactly quantify the damages to rural communities from
flooding. The Lewis County 2007 Flood Disaster Recovery Strategy
(Cowlitz-Wahkiakum Council of Governments, 2009) determined that there
were nearly 15 million of Federal funds allocated to 22 units of government
or non-profit corporations as a result of the December 2007 flood. This
included six fire districts, and the rural communities in Adna, Napavine, Pe
Ell as well as the Boistfort School and Water District. Lewis County and the
larger cities of Chehalis and Centralia, also received extensive federal
assistance as did the Port of Chehalis, Chehalis-Centralia Airport, Centralia
Public School District, Centralia Christian School, and Providence Health
Care System. The 2009 report indicated that there were 9,222 acres of
agricultural land flooded in unincorporated Lewis County, which is 23% of
the 39,861 acres of agricultural land in Lewis County.
Physiography and Geology
Vashon glaciation, which is the third stage of Frazer glaciation (16,000 yrs
to 12,000 yrs BP), deposited coarse sand and gravel in the central basin
surrounding what is now Centralia. The Puget Sound Lobe of the Cordillean
ice sheet, which occupied the Puget Sound lowlands, terminated just north of
Lewis County (Figure 3a).
As the Vashon glacier receded a series of proglacial lakes formed filling the
main trough of Puget Sound and inundating the southern lowlands. Glacial
Lake Russell was the first such large recessional lake. From the vicinity of
Seattle in the north, the lake extended south to the Black Hills, where it
drained south into the Chehalis River. Sediments from Lake Russell formed
13
the blue-clay identified as the Lawton Clay. Lake Russell was thought by
Bretz (1913) to have had an elevation of 110 to 130 feet above sea level.
The second major recessional lake was the glacial Lake Bretz. It drained to
the Chehalis River until glacial ice in the Leland Valley between present day
Quilcene and Discovery Bay in the northeast Olympic Penninsula melted,
allowing the lake’s water to rapidly drain north into the Straits of Juan De
Fuca.
The maximum extent of Vashon Glaciation, and drainage routes are shown
in Figure 3a. (Noble and Wallace, 1966). As shown in Figure 3a, glacial
meltwater flowed down the Skookumchuck River to the Chehalis River
where it dumped a large quantity of gravel. The Skookumchuck River has a
steeper gradient than the Chehalis (see Figures 3c verses 3b). The gravels
which entered the Chehalis River valley at Centralia, constitute the most
southern advance of Vashon outwash into Puget Sound. The Chehalis Valley
was filled to an elevation of about 188 feet, which is considerably above the
pre-Vashon valley bottom. Excavations of the gravel in Centralia exceed 75
feet of depth.
The gravel deposited at Centralia then created a dam across the Chehalis
River which created what Bretz called “Lake Chehalis”. The following is a
description of the Lake Chehalis area by Bretz (1913): “The city of Chehalis
is about four miles up the river from Centralia, and stands at the same
altitude on the same flood plain. But whereas outwash gravels are at least 75
feet deep beneath Centralia, Chehalis is built of a valley fill of river alluvium
and lacustrine deposits, and no trace of glacial gravel has been found in the
region, except where transported by a human agency. The region of the city
of Chehalis received no gravel because the flowing water turned
downstream on entering Chehalis Valley at Centralia and the invading
gravels were carried back toward the glacier. Only standing water could
have existed at the site of Chehalis when the gravels were deposited, for the
valley was dammed by the outwash about Centralia and water must have
backed up the Newaukum, Chehalis, and “Big Swamp” valley.” (Bretz,
1913)
Figure 3b shows the Chehalis River in profile view. The channel bottom at
the lower end shows the deposition from the Skookumchuck that causes the
river at low flow to run uphill. However, if one views the flood profile they
see the extensive flattened area starting at about Chehalis and extending
through to Centralia. This flattening reflects the lake formed when the north
14
outlet of the Chehalis River was blocked. Figure 3c shows a profile of the
Skookumchuck River, without the flattening reflected in the Chehalis
profile. Some of the Chehalis Basin streams have an irregular stair stepped
stream profile such as shown for the Newaukum River in Figure 3d. At the
end of the ice age, meltwater from the glaciers in Puget Sound flowed down
the Black River and lower Chehalis River as shown in Figure 3a.
Bretz in 1913 (p.122 and 123), gave the following explanation for how the
dammed up glacial lakes drained: “But in Puget Sound all water escaping
from glacial lakes in the different valleys was forced to pass over the
Chehalis Sound divide into one drainage line. The result of this control of
glacial drainage by one pass was to limit subsidence of ponded waters whose
valleys had successively lower outlets exposed by ice retreat. Gradually
waters in the troughs and fjords of sufficient depth in the southern part of the
area united at a common level that was determined by the Chehalis Sound
divide east of the Black Hills. The water body thus controlled was named
Lake Russell.” The common level of Bretz Lake was about 160 feet msl
and represents a lake level drained by way of the Black River.
During the time that Vashon Ice occupied Puget Sound south of Everett,
most of western Washington drainage that now enters Puget Sound from the
east, had to flow south through the Black River, past Gate, to the Chehalis
River and then to the Pacific Ocean. After the Straits of Juan de Fuca
became free of ice, and northward drainage into Puget Sound returned, the
Black River draining to the south became an underfit river. The river’s
drainage area became too small and the river’s cross section developed by
Pleistocene runoff, was too wide to transport its available sediment load.
The older Chehalis Basin before the most important, Pleistocene and
Holocene events that control the present physiograph includes, the Cascade
Mountains, the Puget Lowlands, the Coast Range and the Willapa Hills. The
Cascade Range was formed by uplifting of tertiary age basaltic lavas,
pyroclastics, and sedimentary rocks. The uplift of the Cascade Range began
during the late Pliocene Epoch and continued on into the Pleistocene Epoch,
a period of approximately six million years. Pleistocene glaciation has
modified the topography in the northern and eastern portions of the Chehalis
Basin. The Cascade Mountains province is characterized by rough and
mountainous volcanic headlands and their foothills. Much of the land is
above 2,000 feet. Alpine glaciers in the Olympic Mountains had a major
impact in sculpturing the upland present topography.
15
The Willapa Hill Physiographic province extends from the Pacific Ocean
upstream to the central basin. The Chehalis River side hills, terraces and
flood plain make up the topography of this province. Exposed rock within
the Willapa province is composed of Tertiary age marine and nonmarine
sedimentary rock with interbed volcanic rocks. These rocks were deformed
in the late Tertiary Period.
The Puget Sound Trough is a structural basin, and extends into the foothills
of the Cascade Mountain, the Willapa Hills and Olympic Mountains of the
Washington Coast Range. The Chehalis Valley is in the southern end of the
Puget Trough and is presently characterised by a broad, well developed
flood plain and low terraces surrounded by highly dissected uplands of low
to moderate relief that have broad rounded ridges. Valley bottoms are at an
elevation of about 150 feet, and uplands range from 300 to 600 feet.
The Chehalis River is the main drainage in the Chehalis Basin. Its tributaries
start in the hills west of Doty, and flow generally eastward to Chehalis
where the river turns abruptly to the north (Figure 1). The Chehalis flows
north into Thurston County near Centralia. From near Grand Mound, the
river flows northwestward to Elma, and then flows westward to Grays
Harbor. A major tributary draining the Boistfort Valley is the South Fork
Chehalis River, which heads up in the hills southwest of Curtis. Other large
tributaries are the Newaukum River which has its headwaters in the
foothills of the Cascades on the south eastern side of the basin, and the
Skookumchuck River that has its headwaters in the foothills of the northeast
portion of the basin. In addition, the Wynoochee, Satsop and Hoquiam
Rivers are large tributaries that have headwaters in the southern flank of the
Olympic Mountains in Grays Harbor County. The Humptulips and Wishkah
Rivers also have their headwaters in the Olympic Mountains and flow into
Grays Harbor. In the mid-basin, Black Lake originates in wetlands at the
northeast part of the the basin. Most of the Chehalis Basin is lowlands, with
elevation varying from sea level to 5,000 feet.
The 2003 US Army Corps of Engineers report states that geologic evidence
indicates that the Chehalis River has reworked its valley since the deposition
of sand and gravel outwash that was derived from the glacial runoff. The
glacial sand and gravel can however still be found in the terraces along the
valley margin. The US Army Corps of Engineers (2003) indicates a time line
for the reworked river deposits of 7,000 to 10,000 years old. The
16
reformation of the meandering river lateral and vertical accretion deposits to
form flood plains in the former lake beds is one of slow aggradation
dominated by silt clay and organic mud. The US Army Corps of Engineers
(2003) study noted that information they received from the NRCS, formerly
SCS, showed that at least 50% of the deposits in the upper five feet of valley
sediments are organic mud, silt or clay. This is consistent with what is
reflected in the block diagram (Figure 10).
The US Army Corps of Engineers (2003) report states that in 1890, the main
stem of the Chehalis River from RM 82 to the mouth became progressively
shallower downstream and increasingly blocked by snags. Many shoals were
documented to be between .05 and 1.0 feet deep. This report (US Army
Corps of Engineers, 2003) also states that the survey plat noted “Plat records
(1833-1860) provide additional accounts of numerous side channels,
sloughs, and ponds hydrologically connected to the Chehalis mainstem, the
Newaukum, and the Skookumchuck Rivers”
Local Topography
There are multiple 7.5 quad sheets that cover the basin. The USGS quad
sheets for each county can be acquired electronically by doing a query of the
GIS (Geographical Information Systems) data base in each county (Lewis
County, 2012; Thurston County, 2012; Mason County, 2012; and Grays
Harbor County, 2012). Aerial photography of the Chehalis Basin includes at
least partial coverage in 1938, 1966, and various flights from 1970 to 2002,
and 2009. The Puget Sound LiDAR Consortium lists all LiDAR data for the
Chehalis basin as collected by them and other entities. The data is available
for all of Thurston County and the mainstem of the Chehalis River in Grays
Harbor County from 2000-2005, portions of Lewis County in 2005 and
2006, and the coastal areas and the Wynoochee River in 2009.
Lewis, Thurston, Mason and Grays Harbor Counties all have a GIS data
center, for the purpose of presenting an interactive web site to allow users to
view tax lots, aerial photos, topographic maps, and flooded areas. Layers
included in the maps are parcels, urban growth areas, zoning, transportation,
streams, aerial photos, topographic maps, proposed Federal Emergency
Management Agency (FEMA) zones, and other layers (Lewis County, 2012;
Thurston County, 2012; Mason County, 2012; and Grays Harbor County,
2012).
17
Land Use
The Chehalis Basin in 1966 (Glancy, 1971) was about 73% forestry, 13%
cropland, 6% pasture; 1% urban, and 10% other. The Chehalis Basin
Partnership, (CBP) reported in 2004 (Tetra Tech/KCM and Triangle
Associates) that there was 7% agriculture. This would be a drop of 12% in
agriculture in 40 years. Commercial dairy, livestock and crop farming
operations are located mainly in the low lying valleys adjacent to the
Chehalis River and tributaries.
Climate
The climate of the area is characterized by cool dry summers and mild moist
winters over most of the basin. The greatest amount of precipitation falls
between the months of October and May. Precipitation varies from a
minimum of 40 inches in the central basin (Chehalis Area) to 220 inches in
the higher elevations in the Olympic Mountains (Wynoochee and
Humptulips) watersheds. Precipitation usually occurs as rain or snowfall at
higher elevations. However, snowfall does not accumulate over any
prolonged period below 2,500 ft. in elevation. Maximum temperatures in the
warmest months are usually in the 70’s occasionally reaching 80 to 90
degrees. Winter temperatures are mild in the mid-basin agricultural areas
and generally range from the mid 30’s to 50’s. River discharges tend to peak
between December and March, but the Chehalis River flowed at or above
bankfull for much of April in 2012.
Surface Water
Annual and Mean Flows
Surface water annual streamflow follows the variation of climate and annual
precipitation as is discussed above. Stream flow has been measured by the
U.S. Geological Survey (USGS) at stream gaging stations located at various
locations in the basin since approximately 1929. The mean annual
streamflow measured at the existing stream gages over their period of record
varies from 3.14 cubic feet per second per square mile of drainage area
18
(csm), or an annual mean runoff depth of 42 inches for the Skookumchuck
River, to 10.3 csm or 140.1 inches of mean annual runoff depth, for the
Humptulips River. Table 3, also shows the mean of the average annual
runoff for sites on the Chehalis River, Newaukum River, Skookumchuck
River, Satsop River, Wynoochee River, and Humptulips River. The highest
annual mean streamflow and lowest annual mean stream flow for the period
of record of these sites are also shown on Table 3.
The streamflow rates vary throughout the year as well as varying at different
locations in the Chehalis Basin. Table 4 shows mean monthly streamflow at
selected USGS stream gaging stations. Since for precipitation, winter is the
wet season and summer is the dry season, mean monthly stream flow has the
same annual pattern as precipitation, with stream flows that are generally
highest in December and January and lowest in August. The maximum and
minimum mean monthly streamflow for each month is also shown at each
selected gaging station on Table 4, for the period of record of the gage.
The mean annual and mean monthly stream flows are essentially a summary
of the mean of the daily measured streamflow. Table 5 shows the highest
and lowest mean daily stream discharges measured at each of the selected
USGS stream gage stations. Also shown is the date on which those highest
and lowest mean daily flows were measured. Additionally, Table 5 presents
what streamflow rate at each site was exceeded 10 percent of the time, 50
percent of the time, and 90 percent of the time.
Regulatory minimum instream flows were established by the Department of
Ecology (DOE) for 31 control points in the Chehalis Basin in 1976. (Tetra
Tech/KCM and Triangle Associates, 2004). These 31 control points in the
Chehalis Basin were established to continue a healthy stream for fish. An
instream flow study in 2002 looked at streamflow where there was no
historical data, such as the type of data shown in Table 4. This study found
that flows were below the regulatory minimum stream flows for most of the
monitoring period for Chehalis River at the Highway 6 Bridge, Black River,
Newskah Creek, East Fork Hoquiam River and East Fork Wishkah River.
Flows were above regulatory minimum flows before dropping below in
August at the following stations: South Fork Chehalis River, Middle Fork
Satsop River, and Wishkah Rivers. The following stations did not drop
below the regulatory minimum: Cedar Creek, Decker Creek, Johns River,
and West Fork Hoquiam.
19
Since seasonal variations in streamflow are important for water quality and
fish habitat, it is important to be able to make estimates of flow that will
occur as well as what has occurred. As a basis for designing for the future,
flow information is usually presented in a probability format. Two methods
are especially useful for planning and designing:
 Flow duration, the probability a given streamflow was equaled or
exceeded over a period of time.
 Flow frequency, the probability a given streamflow will be exceeded in a
year.
The data presented in Table 5, and discussed above, relative to the
streamflow rate at each site was exceeded 10 percent of the time, 50 percent
of the time, and 90 percent of the time is an example of a “flow duration”
analysis. The “flow frequency” is defined as the probability or percent
chance of a given flow being exceeded or not exceeded in a given year.
Flow frequency is often expressed in terms of recurrence interval or the
estimated number of years between exceeded or not exceeding the given
flows. Guidelines for determining the frequency of peak flow events at a
particular location using streamflow records are documented by the Bulletin
17B (Interagency Advisory Committee on Water Data (IACWD), 1982).
Peak Flows
Table 6a presents estimates for selected frequencies of peak flow rates for
active USGS stream gaging stations in the Chehalis Basin. The relationship
between frequency and peak flow rates at these stream gage sites was
determined by the USGS and published in “Magnitude and Frequency of
Floods in Washington”, USGS Water Resources Investigation Report 974277. (Sumioka, Kresch, and Kasnick, 1998) This report, which was
produced in 1997, included flow data through water year 1996 (October to
September). For the active USGS stream gaging stations listed in Table 6a,
another 15 years of data has been collected since 1966, which changes the
peak flow rate versus frequency relationship. Thus for Table 6a, the Peak
Discharges for the various frequencies were either obtained from recent
Flood Insurance Studies or estimated using the current data and procedures
in Bulletin 17 (IACWD, 1982).
20
Table 6a, includes estimates for the USGS stream gage on the Humptulips
River. This station operated from 1934 to 1979, and was then discontinued.
Prior to 2003, a new site was installed on the Humptulips River 1.0 miles
downstream from the previous site. In order to present an estimate of peak
flow data for the Humptulips River, the gage records were combined for the
1934 to 1979 site and the 2003 to 2011 site. The drainage areas for the two
sites are similar, but there is a data gap between 1979 and 2003.
Table 6b provides a list of discontinued USGS stream gages in the Chehalis
Basin. Unfortunately, due to cut backs in government programs, not all of
the USGS stream gages that have been installed in the Chehalis Basin are
still in operation. The peak discharges at these gages for various frequencies
are not included in Table 6b, because the lack of recent flow events would
affect the accuracy of the discharge versus frequency relationships. The
active stream gages, listed in Table 6a, are co-funded by the following
cooperators:
 Lewis County Public Works
 Skookumchuck Dam, LLC
 Thurston County
 DOE
 Tacoma Public Utilities
 Grays Harbor County
Historic Flooding
The Chehalis and Skookumchuck Rivers were formed by runoff from the
Puget Glaciation and have probably been subject to periodic flows that rise
and over top the banks of these rivers and inundate normally dry land ever
since. The first people who lived in this region probably adapted to the
overbank flows and did not consider the floods as damaging. However, it
has been reported that legends of the Chehalis and Cowlitz Native
Americans include accounts of flooding that occurred before written records
were kept in what is now Lewis County (Cowlitz-Wahkiakum Council of
Governments, 2009). However, following settlement of the area by
emigrants from other parts of the United States, and the building of the
railroad, flooding was considered damaging and events were documented in
written records.
The Centralia newspaper has documentation and reports of 34 flood events
from 1887 to 2007 in Lewis County, 27 of which included the Chehalis
21
Basin, (The Chronicle, 2008; Cowlitz-Wahkiakum Council of Governments
January, 2009). Table 7a lists reported flood events from 1930 to 2010 by
Water Year (October to September) from 9 different sources in the entire
Chehalis Basin. These sources include The Chronicle, Lewis County 2007
Flood Disaster Recovery Strategy, Comprehensive Flood Hazard
Management Plans for Lewis and Grays Harbor Counties, and the Chehalis
Reservation and Flood Insurance Studies for areas in Lewis and Grays
Harbor Counties. The first column of flood dates in Table 7a only reports
the flood events by year, whereas the remaining columns report month and
year. Not all of the flood dates in the first column match up with a flood
date from another source. This indicates that the flood dates in the first
column may include flood events in Lewis County outside the Chehalis
Basin.
The flood events in the Chehalis Basin are not evenly distributed across the
basin. Floods in Lewis County do not always occur in Grays Harbor
County, and likewise floods in Grays Harbor County do not always also
occur in Lewis County.
Documentation of flood events extends back in time to 1887, but records on
the streamflow for the flood events in the Chehalis Basin only extends back
in time to the year 1929 for two of the existing stream gages, and most of the
existing gages were installed much later. So for approximately the first 50
years of documented flood events, we have no stream gage data for
comparison with recent flood events.
As a point of reference, the oldest currently active stream gage in
Washington State is on the Spokane River at Spokane, and this gage has
stream flow records that extend back to 1891. By the year 1919, there were
209 stream gaging stations operating in Washington State, but there were
none in the Chehalis Basin (Parker and Lee, 1923).
Table 7b presents the Peak Discharge at selected Stream Gages for the 35
flood events shown in Table 7a which are listed by month and year. These
tables cover the time period from 1930 to 2010 because the stream flow
records of documented floods do not extend back to before 1930.
Unfortunately, not all of the gages listed have periods of record that extend
back to 1930. But the period of record for all the gages listed extends to
2010 or 2011. The Humptulips River gage does have a period where the
gage was discontinued that extends from 1979 to 2003.
22
The Peak Discharge for Selected Frequencies shown on Table 6a, was used
to determine the flood frequency range for the flood events in Table 7b.
Peak Discharge values alone allow the comparison of different flood events
at a single gage site. But the flood frequency allows the comparison of a
single flood event at different gage sites.
There are flood events shown in Table 7b that do not have any peak
discharge or flood frequency listed for one or more of the stream gages
during the period of record for gage. That is because there is only one peak
annual discharge for each water year, and if peak annual discharge date does
not match the flood date, it is not listed. Thus on water years that have two
or more flood dates listed, there will only be a flood discharge listed for one
of the flood dates at a gage.
As was stated above, Table 7b shows that flood events are not evenly
distributed across the Chehalis Basin. Even the December 2007 event varies
from a greater than 100-year event at some sites to a less than 2-year event at
other sites.
One of the statements that have been made is that in the Chehalis Basin in
the last two decades, four 100-year floods have occurred: in January and
November 1990, February 1996, and December 2007. This statement is
mathematically incorrect. There can only be one 100-year flood at a gage
site in less than a 100 year period. According to Table 7b, the December
2007 event was a 100-year flood at several of the gage sites and the
February 1996 flood was a 100-year flood at the Newaukum River gage site.
But the January and November 1990 events were less than 100-year events
at all the gage sites in Table 7b. So it appears that the correct statement is
that two 100-year floods have occurred in the last decade. The previous
statement about the four 100-year floods, may have been trying to point out
that successive flood events appear to be increasing. If the January and
November 1990 events were analyzed without considering the events in
1996 and 2007 they may be considered to be 100-year events. Table 7b
shows that at the Grand Mound gage site the top 5 peak flow events are the
January 1972, November 1986, January 1990, February 1996, and December
2007 and they successively increase in discharge rate, each one being the
flood of record at the time of the event. There is also a general trend that is
similar at the other gages with floods after 1972 generally being larger than
those before 1972. This is a major area of concern that has not been
investigated.
As shown on Figures 4 and 5, and in Table 7b the gage station recorded a
peak flood of 79,100 cfs in the December 12, 2007 flood that had a
23
frequency of >100 year. This flood caused millions of dollars in urban and
rural area damages.
Map 8 from the Lewis County 2007 Flood Disaster Recovery Strategy
(Cowlitz-Wahkiakum Council of Governments, 2009) shows that most of
the agricultural land on the Lewis County bottomlands has a flood problem.
Based on soils, there were 277,560 acres (SCS, 1972) that have a flood
problem or drainage problem or both. This wetness along with drainage
problems, limits the agricultural use mostly to pasture. However, thousands
of acres have been drained so the actual area with a drainage problem in the
basin should be much less.
Water Bodies
Table 9a lists the number and total area of named lakes in the Chehalis Basin
and Table 9b lists the number, total area and total storage volume of the
dams and reservoirs.
Combining the two tables gives a result of there being 117 lakes and
reservoirs with a total surface area of 5,362 acres in the Chehalis Basin.
The Southwestern Washington River Basin Report (SCS, 1972) noted that
there were 7,146 acres of fresh water lakes and reservoirs in 1972.
However, there was a gross error in the River Basin Report in that it reported
that Lake Sylvia in Grays Harbor County had a surface area of 3,327 acres.
According to DOE, Dam Safety Section, Inventory of Dams, Lake Sylvia is
a small reservoir in Grays Harbor County with a surface area of 32 acres
behind a 32 foot high dam with a maximum storage volume of 510 acre-feet.
It is owned by the Washington State Parks.
Table 9a shows that there are 49 named lakes in the Chehalis Basin, with a
total surface area of 1569.2 acres. HUC 17100104 Lower Chehalis and
HUC 17100105 Grays Harbor (WRIA 22) contain 29 lakes and HUC
17100103 Upper Chehalis (WRIA 23) contains 20 lakes.
The largest lake in the Chehalis Basin is Black Lake in Thurston County
with a surface area of 576.1 acres. Black Lake is unique in that it currently
drains to both the Chehalis Basin and to Puget Sound. This is both unusual
24
and unnatural. Black Lake originally only drained into the Black River and
the Chehalis Basin until 1922, when the Black Lake Ditch was constructed
from the north end of Black Lake to Percival Creek which drains into Budd
Inlet of Puget Sound.
The second largest lake is Nahwatzel Lake in Mason County with a surface
area of 268.8 acres and drains to the East Fork of the Satsop River. The
third largest lake is Duck Lake in Grays Harbor County with a surface area
of 197.0 acres and it drains to Grays Harbor.
Thus, the three largest lakes constitute 66 percent of the total surface area of
the 49 named lakes reported on Table 9a.
The named lakes for Table 9a were obtained from a 1961 inventory of water
resources in Washington State. The lakes listed in the Chehalis Basin were
then verified on recent USGS 7.5 Minute Quadrangle Maps. Some of the
lakes listed on the 1961 inventory were found to no longer exist. Developing
an inventory of unnamed lakes was beyond the scope of this report,
especially since they would have a minimal impact on evaluating flood
reduction alternatives.
Table 9b shows that there are 68 dams and reservoirs in the Chehalis Basin
with a total reservoir surface area of 3,972 acres and a maximum storage
volume of 182,294 acre-feet. The Lower Chehalis and Grays Harbor
watersheds (WRIA 22) contain 16 dams and reservoirs and the Upper
Chehalis watershed (WRIA 23) contains 52 dams and reservoirs.
The largest dam and reservoir in the Chehalis Basin is the Wynoochee Dam
on the Wynoochee River in Grays Harbor County with a maximum storage
of 76,000 acre-feet. This dam was constructed in 1972 by the U.S Army
Corps of Engineers to provide flood control, industrial water supply for the
City of Aberdeen, and to enhance fisheries. Ownership of the dam has been
transferred to the City of Aberdeen. In 1994, Tacoma Power added a
hydroelectric powerhouse one-quarter mile downstream of the dam. The
industrial water supply is stored in the reservoir and released to flow 43.7
miles downstream to the City of Aberdeen diversion. This is the only dam
and reservoir in the Chehalis Basin that was designed to provide flood
protection.
25
The second largest dam and reservoir is the Skookumchuck Dam on the
Skookumchuck River in Thurston County with a maximum storage of
60,000 acre-feet. The Skookumchuck Dam was constructed in 1970 to
provide water to the Centralia Coal Power Plant and is currently owned by
TransAlta. TransAlta also owns the Centralia Coal Power Plant and the
Centralia Coal Mine. The industrial water supply is stored in the reservoir
and released to flow 15 miles downstream to the Centralia Steam Electric
Project (Centralia Coal Power Plant) diversion. This dam was not designed
to provide flood protection.
Of the 52 dams and reservoirs shown in Table 9b for Thurston and Lewis
Counties (WRIA 23), 37 of these dams and reservoirs were constructed as
part of the operation of the Centralia Coal Mine and are owned by them.
Active mining at the Centralia Coal Mine stopped in November 2006 and
operations are now focused on compliance and reclamation activities.
The dams and reservoirs for Table 9b were obtained from the “Inventory of
Dams in the State of Washington” (Department of Ecology State of
Washington (DOE), 2011). Many of the dams inventoried have been
constructed since the Southwest River Basin Report was prepared in 1972.
Estuary
Grays Harbor is the major body of salt water in the basin. It is shaped like a
low-topped boot with the cities of Hoquiam, Aberdeen, and Cosmopolis
(Figure 1) near the boots toe in the eastern part. The City of Westport would
be at the boots heel, and the City of Ocean Shores to the north, near the top
of the boot. Grays Harbor is approximately 15 miles long and six miles
wide.
Grays Harbor provides ocean-going vessels access to the Hoquiam Aberdeen area, and is the main port for numerous fishing vessels. Grays
Harbor is the only coastal estuary in Washington with an authorized deep
water navigation channel. There are 26,603 acres of salt water within the
basin.
Work by Peterson and Phipps (1992) determined the filling rate of Grays
Harbor during the Holocene (last 11,000 years), as sea level rose. Grays
Harbor Valley was at a depth 60 to 70 meters below present sea level. Their
(Peterson and Phipps, 1992) seismic studies and drill coring, established a
26
general textural sequence of sand and mud coarsening upward to sand and
gravel in lower bay reaches, and gravelly sand and sandy gravel fining
upward to sand and mud in upper-bay reaches. Radiocarbon dating of core
sample wood, carbonate shells, and peaty mud yields help them develop a
deposit age curve beginning at 57 meters depth, at 10,760 +/- 90 yrs.
(RCYBP, uncorrected). Average basin sedimentation rates decreased from
1.2 cm. /yr. about 11,000 years BP, to about 8,000 BP. By middle
Holocene (5,000 to 6,000 RCYBP) the filling rate in Grays Harbor
decreased to about 0.1 cm. /yr. That trend corresponded to about a fourfold
decrease in the average rate of basin fill (Peterson and Phipps, 1992). There
would have been episodic coastal uplift and subsidence events (1 -2 meter of
vertical displacement) that influenced the Grays Harbor filling. As
discussed in Reckendorf , et al., (2003) the regional average for 11 Cascadia
sub-subduction events that likely caused subsidence and rebound uplift, is
450 yrs +/- 150 years.
Twitchell and Cross (2002) reported very large volumes of sediment from
the Columbia River system were deposited in Grays Harbor Bay. The extent
and depth of the Holocene aged sediment deposits from the Columbia River
system were mapped and used to indicate how the Columbia River littoral
cell evolved while the ocean levels rose during the last 11,000 years.
The COE in 1882 noted (Powell and Habersham, 1882) that the entrance to
Grays Harbor did not need improvement. They stated they compared the
entrance over 19 years and found that the entrance moved about 1,000 ft.
southward. They also said that the Chehalis River is noted for having gravel
bars, rafts, and snags that are obstructions to travel. The first channel
enlargements were approved in 1892, and were for deepening the channel
2.5 to 3.0 feet over three or four shoals. There were 401 snags removed from
the river in 1899 (Secretary of War, 1900). The COE in 1893 stated that
from the mouth of the Chehalis River to Montesano, for 15 miles, there is 18
feet of water depth at high water, and coasting vessels traverse this portion
of the river. From Montesano to Elma, 16 miles, the river is slightly affected
by tides, and has a general sufficiency for light draft boats. Above Elma, the
river is practically blockaded during the summer and fall by snags and
shallow water.
In 1933, the COE stated that the existing project was 100 feet wide and 18
feet deep at mean low water from the mouth to the junction of the Little
Hoquiam and the East Branch, a distance of 2 miles. They proposed that the
27
project be enlarged to 600 feet wide at the mouth and 30 feet deep. That
channel would decrease to 26 feet deep in Grays Harbor, to the Union
Pacific Railroad Bridge in Aberdeen, and to be between 200 and 350 feet
wide. They also proposed that there be a channel 150 feet wide and 16 feet
deep in the Chehalis River from Cosmopolis to Montesano (War
Department, Office of Chief of Engineers, 1933).
Maintenance dredging for a navigation channel has been continuous for 105
years. The COE has published numerous reports over the years on
maintenance dredging, and on the removal of snags and piles (Abstracts 152
-162, 164, 307 and 523, in Appendix) In 1982, they proposed dredging 24
miles beginning at River Mile (RM) 2.3 on the Chehalis River near
Cosmopolis and ending at Harbor Mile 22, which is 2.5 miles seaward of the
mouth of the estuary.
The volume of materials removed for channel enlargement or maintenance
dredging and the problems related to ocean disposal have increased over the
years. To address some of the concerns for dredging and disposal, the COE
did a study in 1977 (DOE, 1977) evaluated the effects of pipeline dredging,
hopper dredging, disposal in upland dikes, disposal in unconfined tidal areas,
and disposal in and adjacent to the mouth of Grays Harbor. The primary
effects of hopper dredging during the periods of observation were an
increase in turbidity, which was a sediment plume that caused a decrease in
light transmission.
Drainage
There is an extensive system of drainage and drainage ditches in the basin
that have substantially altered the natural wetlands. An example of the
drainage alteration is shown as follows. Figure 6a is a 1938 aerial photo of
the Centralia area, showing extensive wetlands with Reed soil. Figure 6b
shows the same area in 2011. A small area of the wetland was converted to
create Hays and Plummer Lake, as both areas were used for borrow material
to build Interstate 5. However, most of the wetland was drained for urban
development. Interstate 5 was built across the center of the wetland that is
the center of former Bretz Lake. Two other comparisons are shown in
Figures 6c and 6d, near the community of Porter, and 6e and 6f in the
Stearns Creek Basin. The west part of the Porter area has been extensively
drained as shown by the drain ditches and lighter green colors on the colored
28
photograph, verses the wetter pasture and less drainage in the darker green
areas to the right of the state highway. In Figure 6e the 1938 aerial photo
shows an extensive poorly drained dark area on the western (left) portion of
the aerial and dark grey to the north. In Figure 6f the 2011 photo shows
many drainage ditches and lighter colors for land drained for agricultural
purposes.
Sedimentation
There is only one specific study of sediment transport in the Chehalis Basin.
This is the United States Geological Survey (USGS) study, Sediment
Transport by Streams in the Chehalis River Basin, Washington, October
1961 to September 1965. This study of suspended sediment load measured
sediment at 19 different locations. Annual sediment loads varied from
270,000 tons to 690,000 tons. About 74 % of the sediment yield was
derived from Satsop and Wynoochee Rivers. Most of the sediment is
transported between October and April. Table 3 in the USGS Water Supply
Paper 1798-H (Glancy, 1971), shows drainage area, approximate
topographic relief, and the percent of time when suspended sediment load
was transported. During the study period, 90% of the suspended sediment
discharge occurred in 5-10% of the time from headwater streams sample
sites, and 15-20% of the time at lower main-stem sampling stations. The
short intervals are likely peak storm and or landslide related. The Glancy
(1971), USGS study suggests that most of the sediment is derived from
streambank erosion. However, other studies (Pease and Hoover, 1957) have
suggested that sediment is also derived from erosion of landslide. Recent
studies of landslides (Weyerhaeuser, 1994) also indicate the importance of
landslides as a contributor to the sediment load.
The suspended sediment yield in the Glancy (1971) study shows
considerable variation. The yield can be expressed in two ways as shown in
Table 10. One way is in terms of tons per square mile (t./sq.mi.). On that
basis (Glancy, 1971) estimated mean annual suspended sediment at Grand
Mound Gage ( 895 sq.mi.) at about 150 t./sq.mi., but at only 98 t/sq.mi at
Porter Gage ( 1,294 sq. mi.). This can be interpreted that additional drainage
areas tributary to the Chehalis River below the Grand Mound Gage
contribute a much lower sediment yield, for the same drainage area, that
results in a dilution effect at the Porter Gage. In other words there is a much
lower sediment input from side tributaries to the Chehalis River, below
29
Grand Mound compared to above Grand Mound. The Black River is the
main tributary between Grand Mound and Porter and joins the Chehalis
River upstream from the community of Oakville. Glancy (1971)
acknowledged that the Black River contributed little runoff and sediment
yield to the main stem Chehalis River. This difference in sediment yield
between Grand Mound and Porter is most expressed during period of high
runoff.
The other method (Table 10), such as in the USDA, Erosion, Sediment, and
Related Salt Problems and Treatments and Opportunities (USDA, SCS,
1975), expresses sediment yield in acre feet per square mile (ac.ft./sq.mi.).
As shown in Table 10, the sediment yield varies from .07 ac-ft/sq. mi. to
over 1.0 ac.ft./sq.mi. A background rate for a forested watershed with few
landslides is between 0.1 and 0.2 ac.ft/sq.mi. (USDA,SCS, 1975) That rate
seems to fit for many of the watersheds in the Chehalis Basin. However, the
upper Chehalis at Doty (D.A. of 113 sq. mi. at gage), which has an average
annual sediment yield of 0.33 ac.ft./sq. mi., South Fork Chehalis near
Boistfort (D.A. 48 sq. mi. at gage), which has a sediment yield of 0.37
ac.ft./sq. mi. and for Satsop River near Satsop (D.A. 209 ac.ft/sq. mi. )
which has a sediment yield of 0.56 ac. ft./sq. mi. and Middle Fork of Satsop
which has a sediment yield of 0.7 ac. ft./sq. mi., are much higher than the
background rate for forested watersheds.
The mean annual sediment yield of the Satsop River is about 44 % of that
for the entire study area. The suspended sediment yield measured near
Satsop, is considerably greater than any other watershed in the basin except
the Wynoochee River watershed. The Glancy (1971) study noted that some
of the higher sediment yield watersheds like the Satsop (which was 90%
forested at the time of the study) had extensive clearcut areas, but gave no
analysis of their impact. Glancy (1971) indicates that there is extensive
meander migration causing streambank erosion on the Satsop, and the
sampled sediment was coarser grained than many other tributaries evaluated.
However, the contribution of sediment varies significantly among tributaries
of the Satsop, from 0.06 ac. ft. /sq. mi on the East Fork of Satsop to greater
than 1.0 ac. ft. /sq. mi. on the West Fork.
The forest practice regulations have become stricter since the work of
Glancy (1971). For example sidecast road construction on steep, unstable
slopes, which was common the time of the Glancy study, and sediment
yields likely reflect that practice, is no longer permitted. In addition culvert
30
sizing and spacing has increased as well as limiting the size of clearcuts, and
widening the riparian buffer strips.
The Newaukum River, was shown (Glancy, 1971) to have suspended
sediment that varied between tributaries from .17 ac. ft/sq. mi. to .22 ac.
ft./sq.mi. We noted that the Newaukum River stream profile is stair stepped
(Figure 3d), rather than smooth curved as shown for the Skookumchuck
River Figure 3c, or Upper Chehalis Figure 3b. A stair step profile is a
reflection of the river down-cutting and head-cutting reflecting an unstable
heading condition, such as occurs in Stage II of the Channel Evolution
Model (Natural Resources Conservation Service (NRCS), 2007). However,
this potential condition would need to be field checked. In addition, if
headcuts are found they may have worked their way upstream because of
downcutting in the Chehalis River. The bed material along the Newaukum is
mostly cobble showing that the finer fraction is being scoured out. In
addition, the average percentage of coarse grained suspended load (particles
greater than 0.062 mm) of the Newaukum River is about twice that on the
Skookumchuck River.
Glancy (1971) noted, that there was a general decrease in average particle
size from Doty to Porter gages, which indicates that: (1) the proportions of
suspension of fine sediment increases in a downstream direction, (2) more of
the coarser material tends to move as bedload past the two stations and is
therefore not reflected in the suspended sediment load measurements, and
(3) individual particle abrasion in a downstream direction effectively
decreases average particle size.
Upland Erosion
Landslides are a natural occurrence on the forest landscape of Washington
State, but improperly executed forest practices, including sidecast road
construction on steep slopes, poor water management along forest roads and
clearcut harvest of unstable slopes can increase landslide rates. Forest
practices are regulated by WAC 222, which is administered by the DNR.
Most of the landslides in the Chehalis Basin occur on forestland. WAC 22216-050 defines potentially unstable slopes and landforms (Washington State
Legislature, 2012a).
31
The DNR has developed a Landslide Hazard Zonation (LHZ) project. The
goal of the LHZ project is to create an improved screening tool for DNR
regulatory personnel and foresters and landmanagers in identifying unstable
landforms. The purpose is to eliminate error of omission, as much as
possible, for the forest practices permitting process.
Each LHZ consists of a map of known landslides, a map of landslide hazard
areas and a report detailing the landslide hazard findings for a particular
watershed administrative unit (WAU). As each watershed is completed the
information is available to the public through the LHZ completed products
web site. The landslide inventory and hazard zone GIS is available at the
Forest Practices GIS special Data Sets page.
The following LHZ projects are completed in the Chehalis Basin:
1. Upper North Fork and Upper South Fork Newaukum Rivers,
completed in 1994 and included in the Watershed Analysis report
produced by Weyerhaeuser (1999)
2. Chehalis Slough (Serdar and Powell, 2008)
3. Lower Wishkah (Othus and Parks, 2009)
4. Garrard Creek (Paulin and Goetz, 2008)
More dated landslide studies include a study in the Centralia-Chehalis area
of Lewis County (Fiksdal, 1978), and a slope stability map in Thurston
County (Artim, 1976).
The following watershed analyses have been completed for WAUs in the
Chehalis Basin, following the protocol described in WAC 222-22
(Washington State Legislature, 2012a) and the Forest Practices Board
Manual – Section 11:
1. Stillman Creek (Weyerhaeuser, 1994a)
2. Chehalis Headwaters (Weyerhaeuser, 1994b)
3. Upper North Fork Newaukum and Upper South Fork Newaukum
(Weyerhaeuser, 1999)
4. Upper Skookumchuck (Weyerhaeuser, 1997)
5. East/West Humptulips (Lingley, Diem, and Schelmerdin, 2003)
6. West Fork Satsop (Weyerhaeuser and Simpson Timber, 1996)
7. Upper Wynoochee (U.S. Forest Service, 1996)
8. Wishkah Headwaters (Bretherton, et al., 1993)
32
One example of a watershed analysis, is Stillman Creek which is shown
here. Both a hydrologic assessment and a mass wasting assessment
(Weyerhaeuser, 1994b) were conducted for Stillman Creek in Lewis County.
Four types of mass wasting were identified in the Stillman Creek basin. In
order of frequency they were shallow, rapid landslides (132); debris torrents
(40); deep-seated slumps (14); and small sporadic deep seated slides (8)
(Weyerhaeuser, 1994b). Debris torrents accounted for 21% of all landslides
and all of them delivered sediment to the stream system. About 78% of the
debris torrents initiated as road fill failures. In general, they started as very
small to shallow, rapid slides on very steep slopes (~ 100%) in the higher
elevations of basins. They then incorporate flood and spring water and
become a viscous flow. They have been observed to flow down creeks as far
as 2,000 to 15,000 feet. Fifteen of the debris torrents were concentrated in
the upper reaches of the West Fork of Stillman Creek. Shallow rapid
landslides were categorized according to the land use activity associated
with the instability such as: road construction, timber harvesting, streamside
erosion, and natural forest instability. Road instability occurred on moderate
to steep slopes, generally ranging from 30 to 75 % and ranging in size from
very small to very large. However the slope of the road fill was commonly
75 to 100%. About 72% of these road related slides delivered sediment to
the stream. Road related slides were predominantly (75%) associated with
un-compacted sidecast fill material placed on slopes. These fills were
mobilized by saturation of the fill and debris by winter storms, both by direct
precipitation and channelization of surface water owing to the lack of a
culvert, poor placement of the culvert or poor maintenance of the culvert.
Failures of cut slopes on the upper sides of roads accounted for about 21 %
of road-related failures. Weyerhaeuser (1994) noted that such cut slope
failures resulted in the diversion of ditch water across the road, which can
saturate and cause instability of the fill slope.
The Washington State Legislature passed a law that created Road
Maintenance and Abandonment Plan (RMAP). The law became effective in
2000 and is administered by the DNR. The law was revised concerning
small landowners in 2006. The law covers only non-federal land and
requires all large forest landowners, and most small forest landowners, to
submit RMAP’s to DNR.
The goal of the RMAP rule is to have forest roads, excluding orphan roads,
on non-federal land brought up to the standards required by the forestry
33
practices law (Washington State Legislature, 2012a). Originally, the date for
100 % compliance was July 2016. In October 2011, the legislature
authorized an extension of up to five years (2021).
According to the WAC 222-24 (Washington State Legislature, 2012a) all
forest roads, except orphan roads, must be maintained by the owner, until the
road is abandoned. The goals for forest road maintenance are spelled out in
WAC 222-24-010 (Washington State Legislature, 2012a), and include:
1.
2.
3.
4.
5.
6.
7.
8.
Providing fish passage.
Preventing mass wasting.
Limiting deliver of sediment and runoff to typed waters.
Avoiding capture and redirection of surface and ground water.
Providing for passage of some woody debris.
Protecting streambank stability.
Minimizing new roads.
Assuring no net loss of wetland function.
In 2008 (The Upslope Process Scientific Advisory Group) DNR initiated the
Mass Wasting Prescription-Scale Effectiveness Monitoring Project to
determine if the Forest and Fish Rules (FFR) for harvest on potentially
unstable slopes, road construction, and maintenance rules as well as the
RMAP rules, are effective at limiting landslides for forest practices. Two
FFR identified projects have been designated to map unstable landforms.
The Regional Landform Identification Project (RLIP) has been completed
(Dieu, et al., 2011). That project identified and mapped regional landforms
at 1:24,000. Continuing is a LHZ project to map landslides, and unstable
landforms. This mapping is performed at the watershed administrative unit
(WAU) scale, and the focus is on rule-identified landforms, RLIP identified
landforms, and other landforms of concern. Results of both of these projects
are being used as a screening tool to determine unstable slopes and to assist
with the implementation of the unstable slopes rules (Dieu, et al., 2011).
As stated in the 2009 Lewis County 2007 Flood Disaster Recovery Strategy,
some areas in the Chehalis Basin including the Willapa Hills in the Upper
Chehalis watershed that are relatively prone to landslides. Between
December 21, of 2007 and January 17, of 2008, Washington DNR mapped
1,685 landslides. Of these, 1,655 occurred in Lewis County. The DNR
(Sarikhan, et al., 2008) states that their post 2007 storm runoff sample
34
represents between 30 % and 50 % of the landslides that occurred statewide
during the December 2007 storm.
The DNR stated that from their sample, that the most common landslides
were debris slides, many of which were transformed into debris flows.
Sometimes deposits created temporary dams in streams that later burst,
creating a debris torrent or debris flow downstream. During the 2007 flood
landslide debris accumulated on the flood plains as both sediment and as
Large Woody Debris (LWD).
DNR (2008) stated that debris flows created dams downstream from the
landslides. They also created large deposits of coarse material that did not
fully dam the river but obstructed flow. As pointed out by Benda and Dunne
(1997a;b) and by Reckendorf, (2008a;b) the landslide deposit in streams are
reworked by large storms and progress in a downstream direction. These
landslide deposits move as a coarse mass in pulses with large runoff events,
and the streams usually find it easier to erode the streambanks than to move
the coarse material from the landslide mass.
Accelerated Streambank Erosion
Reports such as the Glancy (1971) study of sediment transport and other
studies mention streambank erosion or show a few pictures, but there is no
comprehensive streambank erosion inventory. The LCCD has done a
general study using aerial photos of a sample area in the upper basin, to
identify stream bank erosion locations. A sample map of that study is
presented as Figure 12.
Ground Water
Ground water occurrence is variable within the basin, and depends on local
geology. Variations are due to rock type, thickness, rock alteration and
deformation. In addition, the distribution and type of Pleistocene glacial
deposits has a great influence on shallow ground water sources. The uplands
of the Chehalis Basin are, in general, made up of shale, siltstone, sandstone,
and volcanic rock of Tertiary Age. These rock units have low ground water
yield, and often the water is of low drinking water quality because of
mineral content (USDA,SCS, 1972). Most wells in Tertiary rocks yield only
enough water for domestic use. An exception to this is the Newaukum
35
Watershed that has artesian wells that yield several hundred gallons a
minute. The Newaukum Artesian Basin has an area of 25 square miles, and
lies within a southeast trending syncline. Water taken from the Newaukum
Artesian Basin is from non-marine sedimentary rocks. These areas are
locally recharged from upland runoff.
Chehalis Basin lowlands tend to have Quaternary Age deposits of coarse
grained materials, such as gravel, sand and conglomerate. These are mostly
glacial Pleistocene glacial outwash deposit, and are of major importance as a
source of useable ground water. Glacial-fluvial deposits of sand and gravels
underlie upland plains and terraces to depths of 50 to 200 feet. Well tapping
these deposits usually yield 50 to 150 gallons per minute. Outwash deposits
of sand and gravel deposited from melting of the Puget Sound Lobe are very
permeable, and extend throughout parts of Thurston County, and the
northern edge of Lewis County. A conceptual model of groundwater flow in
the Centralia-Chehalis lowland is illustrated by Figure 7a. A map that
showed the exact location of the Centralia-Chehalis area surfical aquifer was
unable to be located. The city well in Centralia, which has tapped this
aquifer, was yielding 880 gallons per minute (USDA, SCS, 1972).
The primary aquifers in the Chehalis River Basin are comprised of
Pleistocene glacial outwash and Holocene alluvium deposited in valleys of
the Chehalis River and its major tributaries. Intervening deposits of
Pleistocene glacial till and fine-grained inter-glacial sediment act as semiconfining to confining layers. The upper portions of the alpine glacial
outwash within the uplands of the Chehalis Basin have been weathered to
clay, forming a confining unit above the alpine glacial outwash. Although
these units act regionally as aquifers and confining layers, a large amount of
heterogeneity exists within the Quaternary glacial and non-glacial sediments,
resulting in localized areas of high permeability with confining units and low
hydraulic conductivity within aquifers. The areal extent of hydrologic units
is determined by the Quaternary topography of the Chehalis River basin and
the extent of Pleistocene glaciation of both continental and alpine origin
(Gendaszek, 2011).
Erickson (1993) has shown that the Chehalis River between the
Thurston/Lewis County border (RM 60) and Adna (RM 86) hydraulically
interact with an extensive surficial aquifer and serves as a regional ground
water sink. However, samples from 28 wells in the study area show that the
36
water quality is highly variable. Ground water loadings of chloride and
organic loading are highest along the river between RM 72 and 77.5.
The actual water use in WRIA 23 is not known. Recorded water rights and
claims for surface and ground water use equal approximately 937 cfs for
surface and 264 cfs for ground water. Evaluation of 60 miles of the Chehalis
River demonstrates the critical role that ground water discharge plays in
maintaining base flow.
Fasser and Julich (2010) did a study in September 2007 in the Chehalis
Basin to determine gain or loss of streamflow by measuring discharge at
selected intervals within various reaches along the Chehalis River and
tributaries. Discharge was measured in 38 stream reaches at 68 new and
existing stream flow sites, to determine gain or losses. Streamflow gains
were measured for 22 reaches and losses for 13 reaches. No gain or loss was
measured in the Chehalis River, between the Newaukum River and
Skookumchuck River.
The Chehalis River showed a pattern of alternating gains and losses when it
entered the area of wide, gentle relief known as Grand Mound Prairie. The
general pattern was of tributary ground and surface water interaction was
discharge to streams (gaining reaches) in the upper reaches and discharge to
the ground water system (losing reaches) as the tributaries entered the broad
flat Chehalis River Valley. Ground water levels for selected wells in the
Chehalis River Basin are presented in an interactive web-based map to
document the special distribution of groundwater levels in the study area
during late summer in 2009. The data are stored in USGS, National Water
Information System, (NWIS), and Ground Water Site Inventory System
(Fasser and Julich, 2010) .
Water Quality
The primary water quality parameters of concern in the Chehalis River Basin
are temperature, dissolved oxygen, fecal coliform, pH, and turbidity due to
sediment runoff.
The criteria used to evaluate water quality in the Chehalis River Basin are
based on Washington State 173-201A WAC (Washington State Legislature,
2012c). Water quality meeting the standards provides for the habitat needs
37
of fish and other aquatic life, provides a safe environment for people
engaged in water recreation, and provides for the production of healthy and
safe seafood.
Earlier studies of the Chehalis River Basin have reported a wide range of
ambient water quality conditions. In 1970, two fish kills occurred in Wildcat
Creek with 11,000 salmon killed. (Musgrove, 1977). In 1989, a fish kill was
reported on the Black River. Ammonia, nitrites, nitrates, and phosphate
were measured in elevated amounts. The DOE concluded the fish kill was
caused by pollutants discharged to the river. (Yake and Bernhardt, 1989).
In 1992-1993, compared to other Black River tributaries of similar size,
elevated levels of fecal coliform bacteria, phosphorus, ammonia nitrogen,
nitrate nitrogen and nitrite nitrogen were found at Beaver Creek. Additional
water quality problems on the Black River included low dissolved oxygen
and high total phosphorus levels. Two dairies were identified as the sources
of bacteria to the Black River and Beaver Creek (Berg,1995).
Prior to 1994, water cleanup activities began in WRIA 23. Early studies
published by (Sargeant, 1996) and (Sargeant, O’Neal, and Ehinger, 2002)
documented the effects of best management practices (BMP’s) on water
quality in five sub-basins within WRIA 23. Types of BMP’s evaluated
included livestock exclusion, implementation of dairy waste management
plans, restoration of riparian areas, and erosion control practices. Many of
the BMP’s resulted in initial improvements in water quality, however, water
quality degraded in some areas when BMP’s were not properly maintained
and operated.
In 1994 and 1995, DOE collected and analyzed water from the Grayland
Ditch, and found high concentrations of numerous pesticides. Additional
testing was performed in 1996, which continued to find insecticides at
concentrations above state water quality standards. (Anderson and Davis,
2000). There have been improvements in the water quality in recent years.
In 2000, improvements in surface water quality associated with best
management practices (BMP’s) installed in the Chehalis River Basin were
documented. Findings reported all the project areas sampled showed some
water quality improvement due to implementation of BMP’s. (Sargeant,
O’Neal, and Ehinger, 2002)
38
In 2004, the DOE published the Chehalis/Grays Harbor Watershed
Dissolved Oxygen, Temperature, and Fecal Coliform Bacteria TMDL (Total
Maximum Daily Load) Detailed Implementation Cleanup Plan (Rountry) to
guide water cleanup in the basin. Since the completion of this plan, the CBP
has continued to monitor water quality in the basin to determine if it has
improved.
From 2006 -2009, up to 94 sites (See Figure 7b) were used to collect and
analyze water samples on a monthly basis for dissolved oxygen, pH,
temperature, turbidity, and fecal coliform (Green, Loft, and Lehr, 2009). The
report concluded that, although there are general trends in water quality
throughout the Chehalis Basin, specific needs for restoration and
preservation of water quality will need to be evaluated on a site-specific
basis.
In the samples dissolved oxygen concentration levels varied considerably
both between sites and also depending on season. Dissolved oxygen was
generally higher in the winter and lower in the summer. Cold water can
retain a higher level of dissolved oxygen. Dissolved oxygen concentrations
were generally higher in tributary streams further upstream, such as the East
and West Forks of the Humptulips River, the Wynoochee River, and the
Skookumchuck River, and lower in the mainstem Chehalis River and
tributaries at downstream sites near their confluences with the Chehalis
River.
Measured fecal coliform levels were the highest in streams flowing through
residential areas, such as Winter Creek, which flows through Westport,
Ocean Shores Creek, which flows through Ocean Shores, and Hoquiam
River where it flows through the City of Hoquiam.
Typically, pH fell within the range of 6.5 to 8.5 at all 94 monitoring sites,
with very few exceptions. This indicates that water quality in the monitored
streams is in good condition with respect to pH, and that pH is probably not
a limiting factor for distribution or abundance of fish or other aquatic life in
the Chehalis River Basin.
Turbidity was found to be generally highest during the winter months,
especially after storms and flood events, and lowest during the summer
months. Excess sediment can be associated with land use management
practices, including logging roads, landscapes without vegetation, and areas
39
of excessive streambank erosion. During severe flood events, landslides and
debris flows can contribute large amount of sediment to the streams in the
Chehalis River Basin (Green, Loft, and Lehr, 2009). Slope failures and
landslides in the upper Chehalis basin, caused by high rain events in the
winters of 2007 through 2009, were the major cause of elevated turbidity
levels.
Temperature monitoring in the Chehalis River Basin showed the most
frequent warm water temperatures occurred during July and August along
the mainstem Chehalis River, and in larger tributaries near their confluences
with the Chehalis River. Temperature conditions were cool and met the
criteria for salmon and trout rearing most consistently at sites furthest
upstream and/or during the fall, winter, and spring months (see Figure 7c).
Overall, this study indicated a wide range of water quality conditions in the
Chehalis Basin, ranging from relatively undisturbed to severely degraded.
Since the completion of this plan, the CBP has continued to monitor water
quality in the basin to determine if it has improved.
In 2010, when the results from the upper Chehalis water monitoring program
were compared to current water quality conditions their data indicated a
reduction of fecal coliform levels had occurred from 1991-2009. Analysis
of temperature, dissolved oxygen, and turbidity data collected at Porter and
Dryad indicated little to no change had occurred. (Collyard and Von Prause,
2010).
The Federal Clean Water Act (CWA), 1972, requires all states to restore
their waters to be “fishable and swimmable.” Washington's current 2008
Water Quality Assessment, the 303(d) list, shows the water quality status for
water bodies in the state, including the Chehalis River Basin. “The 303(d)
list comprises those waters that are in the polluted water category, for which
beneficial uses– such as drinking, recreation, aquatic habitat, and industrial
use – are impaired by pollution.” (DOE, 2009).
The current Environmental Protection Agency (EPA) assessment is
scheduled to be updated with data collected by May 1, 2011 and submitted
by August 31, 2012. The new assessment will provide the most up to date
and comprehensive information on water quality in the Chehalis River
Basin.
40
Fluvial Geomorphology
Natural rivers vary in form from straight to meandering to braided.
Understanding rivers and the process of their formation is the Science of
Fluvial Geomorphology. By definition, Geomorphology is the scientific
study of landforms and the history and processes involved their formation.
Fluvial Geomorphology is the scientific study of the form (cross section in
terms of width and depth); pattern (shape as viewed from the air); and
profile (slope) of streams and the process and materials involved in a
streams formation over time. The best way to understand streams is to
classify them in accordance with the Rosgen Stream Classification System
(1996), because in doing so one collects most of the essential data needed to
do a stream evaluation. Such an evaluation system is the Rosgen System
shown in Figure 8a.
Leopold, Wolman, and Miller (1964) established that the controlling factors
in development of a river are width, depth, slope, velocity, discharge, size of
sediment, and roughness of the stream channel. To this could be added
streambank materials, streambank stratigraphy, and riparian vegetation. The
bankfull width, depth, slope, sinuosity, and bed material size would be
obtained in the process of collecting the data to utilize the Rosgen Stream
Classification System.
Understanding the fluvial geomorphology of a river will allow any activity
along the river and its associated flood plain such as habitat restoration,
riparian planting, large woody material removal or placement, riprap, drop
structures, levees, sedimentation, dredging, gravel removal, and flooding to
be placed in perspective with respect to cause and effect. The Rosgen
Stream Classification System (Figure 8a) of any given stream reach in
combination with the Channel Evolution Model (NRCS, 2007) (Figure 8b)
to determine a rivers trends in terms of downcutting and widening are basic
to the understanding of any river. In addition, one should make a
determination of the bed material pattern by a system like the planform
characteristics given by Montgomery and Buffington (1997a; 1997b; Figure
9). The use of all three systems provides most of the essential information
needed to do stream work of any kind (i.e. in stream habitat restoration,
streambank protection or riparian planting). Use of the Montgomery and
Buffington (1997b) system will allow the river reaches to be classified as
Cascade, Step-Pool, Plain Bed, Pool/Riffle, or Dune/Riffle. The primary
41
missing components that must be added for a comprehensive physical
stream evaluation are bankfull flow depth, discharge, and frequency of
bankfull peak flows, and an evaluation of the streambank erosion and its
causes, and riparian vegetation. Other important stream physical data like
overhead cover and submerged cover, should also be determined as part of
an aquatic habitat analysis.
We found only two studies in the lowlands that include any kind of fluvial
geomorphic analysis. The US Army Corps of Engineers (2003) study noted
that between the confluences of the Newaukum and Skookumchuck Rivers
the Chehalis River is meandering with a sinuous single-thread channel and
wide flood plain. As measured from 7.5’ topographic maps the sinuosity of
the main stem was shown to have a sinuosity (channel length divided by
valley length) of 1.95 whereas the reach immediately downstream from the
Skookumchuck River mouth has a sinuosity of 1.7. In contrast, the lower 4
miles of the Newaukum River was measured to have a sinuosity of only 1.39
and the lower Skookumchuck River of 1.5.
The US Army Corps of Engineers (1971) noted that there was an absence of
logjams that would have provided a mechanism for maintaining multi-thread
channels. They (2003) also state that in the absence of a large sediment load,
the removal or loss of LWD eliminates the mechanism for forming new side
channels and can lead to abandonment of existing side channels as the main
channel incises and flattens over time. Aerial photos evidence shows that
there are many abandoned channels from natural neck and chute cutoffs,
which would be expected along a meandering stream. There is little
evidence of a multi-channels system on the 7,000 to 10,000 year old flood
plain that would have been altered if LWD was removed. In addition the
downstream evidence of extensive LWD in the Chehalis River system would
indicate that there was extensive LWD present throughout the Chehalis
River system as it functioned as a meandering, not as a multi channel
braided stream. Many chute and neck meander cut offs reflected in the
aerial photography, may have been LWD created avulsions.
This US Army Corps of Engineers (2003) study was a cursory look at
sinuosity and slope based on a study of USGS 7.5 minute Quads. This
method is probably the worst of the methods to obtain accurate data for
slope and sinuosity, because of small scale of maps, and the inaccuracy built
into drawing the stream line on the map by the map makers. Slope should be
measured in the field, and sinuosity on aerial photographs, or LiDAR.
42
The other study was of bankfull conditions at USGS gages, (Castro, 1996).
She determined for the Chehalis River at the Doty stream gage the stream
type, bankfull discharge, bankfull frequence, bankfull depth and width,
channel slope, stream sinuosity and bed material class. There may have
been fluvial geomorphic data collected as part of watershed analysis in the
uplands, but investigating those studies for fluvial geomorphology
information was beyond the scope of this evaluation.
Wetlands Habitat
As stated in Tetra Tech EC, Inc.(2010, p.2-3) the jurisdictional basis for
managing wetlands in the Chehalis Basin is as follows:
Federal Jurisdiction
Under Section 404 of the Clean Water Act (CWA), [COE] and the
[EPA] regulate the discharge of dredge and fill material into “waters
of the United States.” The jurisdictional status of wetlands and other
waters is generally based on the [COE] Jurisdictional Determination
Form Instructional Guidebook ([COE] 2007 cited in Tetra Tech EC,
Inc, 2010) and [COE] guidance resulting from the 2001 Supreme
Court decision Solid Waste Agency of Northern Cook County
(SWANCC) v. United States Army of Corps of Engineers (Findlaw
2001 cited in Tetra Tech EC, Inc, 2010) and Clean Water Act
Jurisdiction Following the U.S. Supreme Court’s Decision in Rapanos
v. United States & Carabell v.
United States ([COE] 2008a cited in Tetra Tech EC, Inc, 2010). In
order for an aquatic feature to be considered a “waters of the U.S.” it
must be at least one of the following:
• A traditional navigable water (TNW)
• A wetland adjacent to a TNW
• A relatively permanent water (RPW), including tributaries that
typically flow year-round or have a continuous flow at least
seasonally (typically three consecutive months depending on the
region)
• A wetland that directly abuts a RPW
43
• A wetland adjacent (proximal but not abutting) to a RPW, but
only if it can be shown that the feature has a “significant nexus”
with a TNW
• A non-RPW or wetland adjacent to a non-RPW if the feature has
a “significant nexus” with a TNW ([COE] 2007b cited in Tetra
Tech EC, Inc, 2010).
Adjacent is defined as “bordering, contiguous, or neighboring.”
Wetlands separated from other waters of the U.S. by barriers such as
natural river berms, man-made dikes, and beach dunes may be
considered adjacent wetlands. The 2008 ruling also requires that the
agencies not generally assert jurisdiction over the following features:
• Swales or erosional features (e.g., gullies or small washes
characterized by low volume, infrequent, or short duration flow);
and
• Ditches (including roadside ditches) excavated wholly in and
draining only uplands and that do not carry a relatively
permanent flow of water. Recent agency guidance states that the
agencies will apply the significant nexus standard as follows
([COE] 2007a cited in Tetra Tech EC, Inc, 2010):
• A significant nexus analysis will assess the flow characteristics
and functions of the tributary itself and the functions performed
by all wetlands adjacent to the tributary to determine if they
significantly affect the chemical, physical and biological integrity
of downstream traditional navigable waters; and
• Significant nexus includes consideration of hydrologic and
ecologic factors.
In the absence of adjacent wetlands, lateral jurisdiction over nontidal
waters extends to the ordinary high water mark (OHWM). The
definition of the OHWM is “that line on the shore established by the
fluctuations of water and indicated by physical characteristics such as
a clear natural line impressed on the bank, shelving, changes in the
character of soil, destruction of terrestrial vegetation, the presence of
litter and debris, or other appropriate means that consider the
characteristics of the surrounding areas” (65 Federal Register 12823,
2000 cited in Tetra Tech EC, Inc, 2010).
44
State Jurisdiction
The DOE regulates wetlands and other waters through the state’s
Shoreline Management Act (SMA) and Growth Management Act
(GMA). Under the SMA, each city and county adopts a shoreline
master program that is based on state guidelines but tailored to the
specific needs of the community. The GMA regulatory framework
requires that each county have a Critical Areas Ordinance (CAO)
program. The county’s CAO provides specific rules for protecting
Critical Areas. Critical Areas include as example, wetlands,
floodplains, aquifers, and steep slopes (Grays Harbor County 2010,
Lewis County 2010 cited in Tetra Tech EC, Inc, 2010). The CAO for
Lewis County, Article IV (A) provides wetland and stream
classification guidelines for determining protective buffers, allowed
activities within wetlands and buffers, and guidelines for mitigation of
impacts to wetlands and buffers. In general road maintenance and
improvement and utility line activities are allowed uses subject to the
priorities, protection, and mitigation requirements of the code. The
Grays Harbor County Code 18.02 provides similar guidelines in
addition to requiring “mitigation sequencing” (impact avoidance,
minimization and mitigation) to conserve wetlands and other waters.
Exemptions to or modifications of wetland area requirements and/or
buffer averaging may be applied at the discretion of the County
planning departments for low intensity activities such as those
associated with maintenance within utility corridors (Grays Harbor
County 2010, Lewis County 2010 cited in Tetra Tech EC, Inc, 2010).
Because of the extensive formations of somewhat poorly to poorly drained
soils along with the wide extent of flooded soils, there are hundreds of
thousands of acres of hydric soils in the Chehalis Basin. Some of these areas
would be classified as prior conversion prior to the development of the
United States Fish and Wildlife Service (USFWS) wetland maps in the
Chehalis Basin. Basically all types of wetlands from Riverine, to Palustrine
to Lacustrine, to Estuarian, would occur in the Chehalis Basin, but the
Palustrine would be the most common. The Riverine are freshwater
emergent with non-woody plants rooted in soils that are saturated at least
part of the time with most of the plant emerged above the surface. The
Palustrine scrub-shrub and forested wetlands in the basin can be separated as
seasonally inundated, seasonally saturated or semi-permanently saturated.
45
The US Fish and Wildlife Service (2012) maintains an online National
Wetlands Inventory. This interactive website allows the user to download
GIS data. Using this data, it was determined that the Chehalis Basin has
329,064 acres of wetlands. A significant portion of this wetland habitat is
located in WRIA 22. Some map information about the wetlands in the
Chehalis Basin in Lewis and Grays Harbor Counties is available from their
respective counties GIS departments.
As a generalization, most of the area shown as flooding also has a historical
drainage problem. We were not able to determine the acreage of Prior
Converted Croplands or Farmed Wetlands. Both of them terms have a
specific meaning and are regulated by DOE. Prior Converted Cropland is a
wetland that was converted to agricultural use prior to December 23, 1985
and is still being farmed. Permission is required to convert this land to a nonagricultural use. If standing water is present for 14 or more days per year it
would be considered Farmed Wetlands. (DOE, 2012) However, a database
of conversion was unable to be located. Hydrophytes will become
reestablished, on this altered land, if farming is discontinued.
There has been extensive drainage of wetlands in the Chehalis Basin as
previously discussed under drainage. Figures 6a – 6f show a comparison of
a 1938 photo where the Reed and other proorly drained soils give a very
dark tone to the aerial photographs verse the same area in 2011, many years
after drainage was established.
Studies by Henning, Gresswell, and Fleming (2006) have looked at the
degree and extent of juvenile use of enhanced and unenhanced emergent
wetlands within the flood plains of the lower Chehalis Basin. His results
suggest that enhancing freshwater wetlands via water control structures can
benefit juvenile salmonids by providing conditions for greater growth
survival emigration.
Simenstad, et al.,(2001) did a study to monitor the development and
ecological status of a constructed estuarine slough. Their report describes the
functional performance of a somewhat atypical estuarine wetland slough one
decade after its creation. The slough was created as mitigation for the loss of
shallow intertidal habitat for migrating juvenile salmon. An adjacent natural
slough served as a reference or control habitat in their evaluation. The study
compared structure (geomorphology, vegetation, and LWD) and ecological
function (fish utilization and prey resources) between the two sloughs.
46
During the monitoring period Simenstad, et al., (2001) found that, within
the constraints of natural and sampling variability, rapid and increasing
similarity between the created and reference estuarine sloughs.
The Chehalis River Surge Plain (CRSP) Natural Area Preserve (NAP) is
located on the Chehalis River between Montesano and Cosmopolis in Grays
Harbor County, WA. DNR designated the NAP in 1989 to protect the largest
and highest quality surge plain wetland in the State of Washington. It also
protects two animal species federally listed as sensitive in Washington: the
bald eagle and the Olympic mudminnow. In 2008, the DNR (2008) initiated
the management planning process for the lands it manages within the NAP.
The purpose of the plan is to define strategies to protect the primary
ecological features of the site, and identify opportunities for outdoor
education and low impact public use. The plan outlines management goals
for the NAP and lists strategies and actions to support the goals. These goals
include to protect the site’s primary natural features, provide for public
access compatible with the management plan. The plan covers a small
wetland along the Chehalis River and pertains to ecosystems and rare and
endangered species (DNR, 2008).
Between 1900 and 1980, Grays Harbor Estuary had an overall net decrease
in tidal wetland due to extensive diking and filling activites, particularly in
the upper part of the estuary (Sandell, et al., 2011). A more recent analysis
of historical estuarine habitat change detailed a 22% decline in tidal flats due
to upland conversion at the mouth of the Grays Harbor, and along the north
channel. There was an increase in eelgrass habitat (1,793 hectares) and an
increase in areas below extreme low water (409 hectares), mainly due to
deepening of the channel for navigation, near the mouth of the estuary.
These actions impacted one stock of spring chinook salmon, one stock of
summer chinook, seven stocks of fall chinook, seven stocks of coho salmon
two stocks of chum salmon, two stocks of summer steelhead trout, and eight
stocks of winter steelhead. In additon, cutthroat trout have been previously
found throughout the drainage, and bull trout have been document to be
present (Sandell, et al., 2011).
Aquatic Habitat
Fish in the taxonomic family Salmonidae (salmonids) in the Chehalis River
Basin include chinook salmon, chum salmon, coho salmon, steelhead trout,
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coastal cutthroat trout, and char (bull trout and Dolly Varden) (Washington
Department of Fish and Wildlife, 2012). The species of most importance for
commercial and recreational fishing include the three Pacific salmon species
and the steelhead trout.
Salmon spawning and escapement in the Chehalis Basin were summarized
in the 1975 publication, A Catalog of Washington Streams and Salmon
Utilization, Volume 2 Coastal Region, Washington Department of Fisheries
(Phinney, Bucknell, and Williams, 1975). Table 11, adapted from that
report, shows timing of salmon fresh water life phases in the Chehalis Basin.
Virtually all of streams in the Chehalis Basin had sufficient spawning areas
in their pristine condition. Over the years, the ideal conditions have
deteriorated so there are now many limiting factors to salmonid production.
There was a supplement to the 1975 catalog, published in 1981
(Bucknell,1981) that describes the location and length of all known streams,
including those less than 1 mile in length, that were not included in the
original catalog. Rive miles, locations of landmarks such as road crossings,
railroad crossings, lakes, dams and gages are included.
Pacific salmon have disappeared from about 40% of the historic breeding
range in WA, OR, ID, and CA. Most runs are now maintained by hatcheries
(Commission of Life Sciences, 1996).
There are many specific projects that have evaluated habitat and watershed
conditions as baseline data for evaluation and enhancement projects. Studies
by Schillinger (1994), are of that type. Other studies have been sub-basin or
basin wide studies such as those by (Wampler, et al., 1993) that looked at
stream habitat degradation, and (Bolton and Shelberg, 2001) that addressed
impacts of flood plain fills, and structures. The study by Boltan and
Shelberg (2001) looked at channel confinement, and modifications to the
hyporheic zone as well as flood plain fills.
Mobrand Biometrics (2003) produced a document that summarizes the
results of an assessment to identify strategic priorities for conserving and
rebuilding salmon and steelhead populations in the Chehalis Basin.
The Endangered Species Act (ESA) prompted the State of Washington to
pass laws regarding salmon habitat that became Chapter 77.85 of the
Revised Code of Washington (RCW) for salmon recovery (Washington
State Legislature, 2012b). Chapter 77.85 expands upon ESA’s purpose of
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preventing salmonid extinction by instructing the office of the governor to
coordinate state strategy to allow for salmon recovery to healthy and
sustainable population levels with productive commercial and recreational
fisheries. The law specifically entrusted voluntary “lead entities” consisting
of counties, cities and tribal governments to develop the projects necessary
for restoring and protecting fish habitat within the state’s 62 Water Resource
Inventory Areas.
Bull trout were listed as a Threatened Species under the ESA in 1999 (U.S.
Fish and Wildlife Service, 2004). In the Bull Trout Recovery Plan, foraging,
migration and overwintering habitat for bull trout on the southern Olympic
Peninsula includes Grays Harbor, Hoquiam River, Humptulips River, and
the lower Chehalis River basin including the Satsop River and the
Wynoochee River (U.S. Fish and Wildlife Service, 2004). On September 30,
2010 the US Fish and Wildlife Service published a Revised Designation of
Critical Habitat for Bull Trout in the conterminous, lower 48 states (United
States Fish and Wildlife (USFWS), 2010).
The state forest practice rules 222-30 WAC (Washington State Legislature,
2012a) require the maintenance and restoration of aquatic and riparian
habitat. As a result, the Forest Practices Habitat Conservation Plan asserts
that the rules and the program are a means of meeting the requirements of
the ESA, as well as those of the Federal Clean Water Act (CWA) for species
included in the plan.
The Washington State Forestry Practices Board has established a
Cooperative Monitoring and Evaluation Research Committee (CMER). The
CMER has a work plan that is organized by Forest and Fish Report rule
groups. A rule group is set of forest practice rules relating to a particular
resource such as a wetland or fish-bearing streams, or to a particular type of
forestry practice, such as road construction or maintenance. There are
presently 12 Rule groups (Cooperative Monitoring and Evaluation Research
Committee (CMER), 2011). An example rule group is the Stream Typing
Rule Group that is trying to develop a multi-parameter, field verified GIS
logistic regression model that accurately predicts the locations of Type F
(fish bearing) and Type N (non-fish bearing) boundaries across eastern
Washington. Another is the Type N Riparian Prescription Rule Group that
is evaluating the effectiveness of the Type N stream riparian prescriptions on
riparian stand condition, fallen trees, LWD recruitment, shade, channel
wood loading and soil disturbance from wind thrown trees.
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The CMER work plan for 2012 (CMER, 2011) list 90 projects that cover a
range of topics related to forest practice rules.These projects are at various
stages of development and completion.
A document has been developed called the Information Structure of
Ecosystem Diagnosis and Treatment (EDT) and Habitat Rating Rules for
chinook salmon, coho salmon, and steelhead trout (Mobrand Biometrics,
2003). Their document explains the rules and information structure of EDT
with specific applications for chinook, coho salmon, and steelhead trout.
The document is used in conjunction with an EDT Rules Viewer software,
that allows users to explore specific effects of EDT rules using the EDT
stream read data.
The Washington Department of Fish and Wildlife (WDFW) (2012)
produced a map based data viewer called Salmonscape for salmon habitat
fish use. This includes data on ESA listing units, gaging station stream
attributes, stock status, fish distribution, and EDT restoration. In addition, it
includes EDT preservation, intertidal forage fish, fish facilities, fish passage
barriers and juvenile fish traps.
A joint wild salmon policy was developed by the Washington Fish and
Wildlife commission and the Western Washington Treaty Tribes to protect,
restore, and enhance salmon productivity. In addition, the policy provides
direction to protect the diversity of wild salmon and their ecosystems, to
sustain ceremonial subsistence, commercial and recreational fisheries, non
consumptive fish benefits, and other related cultural and ecological values
(State of Washington Tribes, 1997). A salmon and steelhead stock
inventory was developed in 1993 as a first step in a statewide effort to
maintain and restore wild salmon and steelhead stock and fisheries
(Washington Department of Fish and Wildlife and Western Washington
Treaty Indian Tribes, 1993).
Mendoza (1998) reported on a six month study to identify and characterize
off-channel aquatic habitat along the Chehalis River and tributaries. They
reported that many areas were cut off from the main river and are no longer
accessible for juvenile fish and suggested remedial action.
There is a WDFW and DOE, Chehalis River Basin (WRIA’s 22 and 23) fish
habitat analysis, using an instream flow incremental methodology (Caldwell,
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et al., 2004). The methodology cannot determine the instream flow for fish
populations, but can only show whether an increase or decrease in stream
flow will increase or decrease the quantity of fish habitat.
The Northwest Indian Fisheries Commission (2005), presented a
comprehensive report on the salmon habitat in the basin. The report is based
on data in the Salmon and Steelhead Habitat Inventory and Assessment
program. The report has several maps detailing land use, ownership types,
stream gradient, habitat types, precipitation, fish usage, and problems in the
watershed. An updated report is to be published in 2012.
There was a limiting factor analyis for salmonids done for the WSCC by
Smith and Wenger, (2001). Later, a limiting factor analysis was done by
Anchor QEA, LLC (2012) for salmonids. The 2012 report for salmonids
suggested that a salmon habitat analysis include fish blockages (impassible
culverts), flood plain condition (incised channels, drainage, or filling of
wetlands), streambed substrate (mass wasting or low woody debris), riparian
condition (tree canopy), water quality (high water temperatures or low
dissolved oxygen), and water quantity (low summer base flows). To these
could be added several physical characteristics: flood plains disconnected
from channel by dikes, flood plain old channels not connected to streams,
accelerated streambank erosion causing excessive sedimentation, inadequate
pool and riffle planform characteristics, inadequate submerged LWD and
stream channels that are too wide and shallow to transport their sediment
load.
Table 1 in the Anchor QEA, LLC (2012) report shows by watershed and
sub-watershed, Tier 1, 2, and 3 concerns for flood plain conditions, fish
passage, riparian conditions, LWD , water quality, water quantity, and
streambed sediment. Table 3 in the Anchor QEA, LLC (2012) study shows
Salmonid potential projects to reduce limiting factors in the Upper Chehalis
Basin. Table 4 in the Anchor QEA, LLC (2012) report shows the LCCD
fish barrier sites, ranked in order of importance.
A total of 15 culvert surveys have been completed in the Chehalis Basin.
The LCCD culvert survey reports by Verd (2002a; 2002b; 2003a; 2003b;
2004a; 2004b; 2004c; 2004d; 2006; 2007b; 2008; 2009a; 2009b) and Mason
Conservation District (MCD) (2007) were all done in accordance with the
Fish Passage Barrier Assessment and Prioritization Manual of the Salmon
Screening Habitat Enhancement and Restoration division (2000). A total of
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2518 culverts and 14 dams were surveyed, of which 1740 were barriers.
Extensive damage from the 2007 and 2009 floods prompted a resurvey of
selected areas in the Upper Chehalis Basin. A total of 82 culverts were
looked at with 39 being rated as impassable Verd (2009a).
There used to be an extensive beaver population in the Chehalis Basin. As
reported by the City of Montesano (2000), the February 1996 flood that
completely surrounded the City of Montesano, washed out every beaver dam
in the streams that had been previously inventoried. That happened again in
March 1997. A 2000 inventory found 161 beaver dams. The City noted that
some of the benefits of beaver dams are sediment control, streambank
erosion, habitat diversity, development of deep pools for fish passage, and
ground water recharge. They (2000) noted the primary negative impacts is
to RMZ trees, and as fish barriers. They can also block culverts but these
impacts can be off-set by beaver deceivers. The Montesano example is
likely to be a common occurrence throughout the Chehalis Basin.
Riparian areas have been extensively lost in the Chehalis Basin. Cramer
(2012) noted that approximately 85% of WA terrestrial vertebrate wildlife
species depend on riparian area habitat for all or critical portions of their life
histories. Figure 11 is a small scale reflection of the existing riparian areas
along streams.
Simon and Peoples (2006) discuss a plan to cooodinate, control efforts for
invasive aquatic weed species in the Chehalis Basin.
Land Resources
Soils
The soils of the basin have been separated broadly into six groups, based on
their geological origin, process of formation and general topographic
features. These groups are as follows;
(1)
Residual soils, or those formed directly from weathering of
underlying rocks in place. These soils include the uniformly finetextured clay loams and silty clay loams of the rolling hills and
uplands, as well as the rough mountainous districts, which varies
from light loams to silty clay or clay loams.
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(2)
(3)
(4)
(5)
Soils derived from alluvial material deposited over former flood
plains of the larger streams or as outwash plains. Included in this
group are soils derived from glacial materials having a light sandy
or gravelly texture, and the soils derived mainly from nonglacial
materials, principally of silt and clay.
Soils derived from recent alluvial flood plain and delta deposits.
These soils occupy the flood plains of the principal rivers, and the
tidal flats and delta land found along the mouths of some of the
larger rivers. These soils are generally made up of fine sand, silt
and clay.
Soils derived from marine beach and from Eolain or wind blown
deposits. This grouping included areas of beach and dund sand,
and is made up of sand or a mixture of sand and gravel. These
soils have limited agricultural use.
Soils derived mainly from accumulation of organic matter. These
soils owe their origin to slow decomposition of the remains of
vegetation under swampy or poorly drained conditions. Where this
organic matter has lost all semblance of its original structure and
has mixed with silt and clay, it is called muck. Deposits retaining
part of their original structure have more the characteristic of peat.
Land Capability
Capability classification is a grouping of soils that shows, in a general way,
the suitability of soils for most kinds of agricultural uses. It is a practical
grouping based on the limitations of the soils, risk of erosion and
sedimentation, and the way the soils respond to treatment. Definitions of
land capability classes follow:
Class I – Soils in Class I have few or no limitations or hazards. They
may be used safely for cultivated crops, pasture, range, woodland, or
wildlife.
Class II – Soils in Class II have few limitations or hazards. Simple
conservation practices are needed when cultivated. They are suited to
cultivated crops, pasture, range, woodland, or wildlife.
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Class III – Soils require more difficult or complex conservation
practices when cultivated. They have more limitations and hazards
than those in Class II. They are suited to cultivated crops, pasture,
range, woodland, or wildlife.
Class IV – Soils are even more difficult to cultivate, and more
complex measures are needed when these soils are cultivated. They
have greater limitations and hazards than Class III. They are suited for
cultivated crops, pasture, range, woodland, and wildlife.
Class V – Soils have little or no erosion hazard, but have other
limitations that prevent normal tillage for cultivated crops. They may
be suited for pasture, range, woodland or wildlife.
Class VI – Soils in Class VI have severe limitation or hazards that
make them generally unsuited for cultivation or pasture. Thay may be
suited to pasture, range, woodland, or wildlife.
Class VII – Soils in Class VII have very severe limitations or hazards
that make them generally unsuited for cultivation or pasture. They
may be best suited for grazing, woodland, or wildlife.
Class VIII – Soils and landforms in this class have limitations and
hazards that prevent their use for cultivated crops, pasture, range or
woodland. They may be suited for recreation wildlife or water
supply.
Subclass limitations (e) erosion. This sub-class is for soils where
erosion is the dominant hazard in their use.
Subclass (w) excess water. This sub-class is made up of soils where
excess water is the dominant hazard or limitation to their use. Poor
soil drainage, wetness high water table , and overflow are the criteria
for determining which soils belong in the sub-class.
Sub-class (s) soil limitations in root zone. This sub-class is made up
of soils where root-zone limitations are the dominant hazard or
limitations in their use. These limitations area the result of such
factors as shallow soils, stones, low moisture-holding capacity, low
fertility that is difficult to correct, and salinity or alkalinity.
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Sub-class (c) climate. This sub-class is made up of soils where the
climate (temperature and lack of moisture) is the only major hazard or
limitation in their use.
In the basin there are 71,545 ares of Class II Soils and 132,954 acres of
Class III soils. There are 256,110 acres of Class IV soils, and 32,713 acres of
Class V soils. In addition there are 704,031 acres of Class VI, 437,893
acres of Class VII soils and 59,705 acres of Class VIII soils. Soils with Subclass (w) designation include 285,942 acres with flooding or drainage
limitations, 1,254,048 acres with Sub-class (e) erosion as their primary
limitation, and 154,961 acres with soil root zone (s) limitations (USDA,SCS,
1972).
The Southwest River Basin report (USDA,SCS, 1972), reported that there
are 277,560 acres with some level of flood problem in the Chehalis Basin.
Of that 9,399 acres had only slight flood damage that occurred only one in
10 years; 18,430 acres that had flooding in one in five to one in ten year
events; and 249,731 acres that have flooding regularly during certain
months during one in five years or less. However, these more frequently
flooded soils may be used for crops later in the year.
Soil surveys were written for Lewis (Evans and Fibich, 1987) Grays Harbor,
Pacific, and Wahkiakum (Pringle, 1986), and Thurston (Pringle,1990)
Counties. Current soils information can be found online.
Based on soils in Lewis County, there are 16,449 acres of the soils (Cloquato
and Newburg) that are frequently flooded and about 13,096 acres (Chehalis)
that are occasionally flooded. These are all well drained soils. The landscape
relationship for these flooded soils are shown in Figure 10 (Evans and
Fibich, 1987), where the frequently flooded Newberg fine sandy loam, is
shown right along, and adjacent to the Cloquato silt loam. The slightly
better developed and less flooded Chehalis silt clay or silty clay loam, where
clay has accumulated in the B horizon, occurs adjacent and higher than the
Cloquato Soils (Figure 10). In Lewis County, the poorly drained soils along
the flood plain and low terrace consists of the Reed soil. The wet Reed soil
is also shown in Figure 10. Reed soils can be divided into the Reed silty
clay loam of which there are 26,025 acres and the Reed silty clay loam
channelized of which there are 1,275 acres. The soils described as
channelized occur in abandoned river channels or on shallow depressional
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areas on flood plains and low terraces. According to the USDA, SCS (1972)
there are 1,000,800 acres that have drainage problems because of soils in the
Chehalis Basin.
Upland Forestry Vegetation
The Chehalis basin is 73 % forestry. Therefore, forest practices that impact
timber harvesting are covered by the Forest Practice Act 222-30 WAC
(Washington State Legislature, 2012a). The Forest Practice Act applies
primarily to non-Federal and non-tribal forestland. Many of these forestlands
contains habitat for aquatic and riparian dependant species that have been
listed (or may be listed in the future) under the Federal ESA.
Clearcutting size and timing is covered in 222-3-025. Rate of harvest
monitoring is covered by 222-3-120. Riparian Management 222-30-021, and
Shade requirements to maintain water temperature ,222-30-040, will be
discussed later under riparian management. (Washington State Legislature,
2012a)
Clearcutting
The maximum clearcut (even aged harvest) size for property under the
control of a landowner is 240 acres. The vegetative cover adjacent to the
premeter of a proposed clearcut must meet at least one of the following
criteria:
1. At least 30% of the permeter is in stands of trees that are 30 years
of age or older.
2. At least 60% of the perimeter is in stands of trees that are at least
fifteen years of age or older.
3. At least 90% of the perimeter is in stands of trees that survived on
a site a minimum of five growing seasons, or, if not, have reached
an average of four feet.
Wildlife trees and logs must be left within clearcuts as follows:
1. Wildlife reserve trees (3) per acre.
2. Green recruitment trees (2) per acre.
3. Down logs (2) per acre.
Wildlife reserve trees and green recruitment trees may be clumped or be
scattered.
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Rate of Harvesting
This rule requires DNR to monitor, beginning in 1992, the rate of timber
harvest on a annual basis for the purpose of examining the relationship of the
rate of timber harvest to sustainability of the timber industry and protection
of public resources.
Riparian Vegetation
Riparian areas have been inventoried by the LCCD and Thurston
Conservation District (2008). These areas include tributaries and the
mainstem of the Chehalis River in Grays Harbor County to Porter, and all of
the Chehalis River Basin in Lewis County. Thurston Conservation District
completed this project for the portion of the Chehalis Basin in Thurston
County. An example map of the location of the riparian areas is shown as
Figure 11. An assessment of riparian conditions of the Lower Chehalis Basin
(WRIA 22) was conducted for streams in the Lower Humptulips, Lower
Wishkah, Wynoochee, Middle Fork Satsop, and East Fork (Bretherton,
2003). Table 8 was developed to illustrate the needs for improved riparian
habitat in Lewis County and the associated costs with establishing a buffer.
Upland Forest Riparian
Riparian Management
Management Zones (WMZs)
Zones
(RMZs)
and
Wetland
RMZs are required along some non-fish bearing water and along all fish
bearing water. WMZs are required along some wetlands. RMZs are required
to be measured from the edge of any channel migration zone when present.
RMZ widths for fish bearing water vary depending upon site class (tree
growing capacity), stream class, and stream width, between 90’ and 200’.
RMZ width for type Np (non-fish perennial) is 50’. Type Ns (non-fish
seasonal) streams are not required to have an RMZ.
RMZs and WMZs are not necessarily “no harvest” zones. Depending upon
the situation, some harvesting is permitted.
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Shade Requirements to Maintain Water Temperature
If any harvesting is proposed within 75’ of bankfull width of a fish bearing
stream, the proponent must perform a shade survey according to the Forest
Practice Board Manual Section 1 (Department of Natural Resources (DNR),
2000).
Cultural Resources
As described in the Tetra Tech/KCM and Triangle Associates (2004) the
Quinault lived on the Olympic Peninsula as members of individual family
groups for thousands of years before a small portion of the land became the
Quinault Indian Reservation. There were no headsman or spokesman for the
tribes until the signing of treaties, when chiefs were chosen.
The cedar tree was the most valuable resource. Quinault houses were made
of large cedar trees split into planks, with gabled roofs measuring 30-60 feet
in length and 20-40 feet in width. Log houses were occupied by two or more
families. Transportation was by ocean or river canoe. The Quinault were the
furthest tribe south to hunt whales. They also hunted seals. Boxes, bowls,
dishes and platters were carved from alder and soft maple. Stone mauls,
hammers, and wedges of wood and bone were used to split cedar.
In the late 1700’s European explorers visited and influenced the Quinault
Indians. By the turn of the century, the coming of the fur trade and white
settlers brought many diseases to the Quinault Indians including small pox,
measles, and tuberculosis. The Quinault signed a treaty with the U.S.
Government on July 1, 1885 along with the Queets, Hoh, and Quileute
tribes. After changes due to objections by the Chehalis, Cowliz, and
Shoalwater Indians at the Chehalis River Council, this treaty was finally
proclaimed by the President on April 1, 1859. Aboriginal territory was now
confined to reservation boundaries, and ceded areas were settled by white
farmers. The Quinault people had to give up hunting and begin farming,
while giant cedar trees were cut down and cleared to make roads to and from
the reservation.
The Chehalis people are another native people of Washington State. They
consist of two divisions: The Upper Chehalis and the Lower Chehalis.
Within these there are several tribes: the Copalis, Wynoochee and
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Humptulips people were part of the Lower Chehalis, while the Satsop people
were part of the Upper Chehalis. The boundary between the two groups is
the confluence of the Chehalis River and Satsop River. The Chehalis
language belongs to the Coast Salish family of languages among Northwest
Coast indigeneous people. This tribe was encountered by employees of the
Hudson Bay Company when they traveled up to the Black River.
The Chehalis people were resettled on their current Chehalis Indian
Reservation along the Chehalis River in 1860. The reservation has a land
area of 6.6 sq. mi in southeastern Grays Harbor County and southwestern
Thurston Counties. Approximately 75 % of the Chehalis Reservation is
located in an active flood plain. They experienced large damaging floods in
1964, 1986, 1990, 1996, and 2007. The number of Chehalis People was 149
in 1906, and by 1984 was 382. As of the 2000 census, the resident
population was 691 persons. The major community within the reservation
are Chehalis Village and the city of Oakville. (Wikimedia Foundation Inc.,
2012).
Families came to live on the Chehalis Indian Reservation but many of the
people lived outside the reservation. The people were concerned about their
land status because they were a non-treaty people and they received less
federal help. On October 1, 1886 President Grover Cleveland, by executive
order set aside 3,753.6 acres of the reservation for homesteads. In addition,
471 acres were set aside for schools (Government of Indian Affairs, 2012).
Ground water is present beneath the Chehalis Indian Reservation. Supplies
available within the depth zone of water level fluculations are estimated to
be between 20 and 60 times that being pumped at the time of the 1977 study
(Pearson and Higgins). At the time of the study ground water quality was
shown to be adequate, but the data is quite old, so later contamination is
possible.
WATER AND RELATED LAND RESOURCES PROBLEMS
AND MISSING DATA
Flooding
Any future work on flood damage reduction and associated erosion and
sediment reduction should be done in the context of the habitat and stream
59
conditions described in this report. The references cited are the key
references to be consulted in determining the next step in evaluation of flood
damage reduction. The streambank erosion and associated damages to land,
and aquatic resources are directly related to stream runoff and flooding.
Figure 4 (Satsop River at Satsop) is a representative stream gage (299 sq.
mi.) in the Chehalis Basin that shows the stream discharge for any given
flood peak elevation. The corresponding average return interval of flooding
for any given discharge at this location is shown in Figure 5. As shown on
Figures 4, and 5 and in Table 7b, this gage station recorded a peak flood of
36,400 cfs in the December 12, 2007 flood that had a frequency of 5 to 10
years at a stage of 36.6 feet. The maximum peak discharge recorded at the
Satsop stream gage was 63,600 cfs in March 1997 at a stage of 38.9 feet.
This shows that for flood events, a relatively small change in flood elevation
can be a large change in flood discharge.
Stage and Frequency at Representative Gage
The USGS stream gages do not record stream discharge, they continuously
record stage or the elevation of the water surface in the stream.
To obtain stream discharge, a relationship unique to each gage is developed
between gage height or stage, and stream discharge. This relationship is
developed by USGS by having technicans make periodic visits to stream
gages, to perform measurements of the water surface elevation, streamflow
velocity, and cross sectional area of the streamflow. The velocity and cross
sectional area are used to calculate the discharge for the measured water
surface elevation.
By making a series of field measurements, a relationship between gage
height and stream discharge is developed, which is usually plotted on log –
log graph paper. An example of the stage versus discharge curve for the
Satsop River at Satsop is shown on Figure 4.
Figure 4 shows data points numbered between 416 and 638, these points are
the discharge and gage heights measured at individual site visits. The rating
curve of elevation versus discharge is shown as a straight line on the log-log
paper and there is also a “shift-adjusted rating” shown.
The “shift-adjusted rating” shows how changes in the stream channel
geometry have affected stream flow within the channel. From looking at the
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Figure 4, it appears that the “shift-adjusted rating” affects three-quarters of
the rating curve. But since Figure 4 has a logrimithic scale, the “shiftadjusted rating” only affects discharges from 100 to 10,000 cfs, and
discharges from 10,000 to 80,000 cfs are not affected.
Figure 5 is the peak annual flow versus frequency relationship for the gage
on the Satsop River at Satsop. The data points are the measured annual peak
discharge values for the period of record, ordered from lowest to highest.
The plotted line on Figure 5 defines the probability or percent chance of a
given flow being exceeded or not exceeded in a given year. Flow frequency
is often expressed in terms of recurrence interval or the estimated number of
years between exceeding or not exceeding the given flows.
Guidelines for determining peak annual flow versus frequency relationships
at a USGS stream gaging station are documented by the Bulletin 17B
(IACWD, 1982).
On Figure 5, the lower end of the annual peak discharge versus probablility
curve ends at a discharge of 10,000 cfs and an exceedance probability of 99.
An exceedance probability of 99 means that for 99 out of 100 years this peak
annual discharge value should be exceeded. Stream discharges less than
10,000 cfs should occur more than once a year at this site.
On Figure 4, 10,000 cfs is at the upper end of the “shift-adjusted rating”
curve. Thus, the shift-adjusted rating only effects flows that normally occur
more than once a year.
Bankfull Discharge
Bankfull discharge is commonly associated with the streamflow that fills the
stream channel to the top of its banks and to a point where water begins to
flow into the floodplain. The bankfull stage and discharge serve as
consistent morphological indicies. Stream dimensions, patterns and bed
features associated with the logitudinal river profile are generally described
as a function of channel width measured at the bankfull stage.
For streams that are entrenched or have no floodplain, a commonly accepted
definition of bankfull is: “The bankfull stage corresponds to the discharge at
which channel maintenance is the most effective, that is, the discharge at
which moving sediment, forming or removing bars, forming or changing
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bends and meanders, and generally doing work that results in the average
morphologic charcteristics of channels” (Rosgen, 1996).
The only known measurements of bankfull discharge in the Chehalis Basin
were made at the three gages on the Chehalis River in 1995 as part of
research project for a Doctor of Philosophy candidate at Oregon State
University (Castro, 1996).
It would be prudent to make current estimates of bankfull discharge at
stream gages on the Chehalis River to see if the bankfull discharge and
channel morphology has changed since 1995. This would give an indication
as to whether the hydrology of the watershed is changing.
Previous Studies
Various government agencies have studies flood problems in the Chehalis
Basin. These include the COE, FEMA, NRCS, and the U.S. Bureau of
Reclamation. The COE has been studying solutions to flood problems since
1931. The U.S. Bureau of Reclamation studied multipurpose land and water
resource development potentials of the upper Chehalis River basin in the
1960’s. The NRCS conducted flood analyses for tributaries in the basin in
the 1970’s.
These studies are listed below, and are described in more detail in the
“Chehalis River Basin Comprehensive Flood Hazard Management Plan”
(Chehalis River Basin Flood Authority, 2010).
 In 1931, the COE investigated improvements on the Chehalis River for
navigation, flood control, power development, and irrigation which were
published in “House Document 148, 72nd Congress.”
 In 1935, the COE developed a Preliminary Examination on flood control
from Centralia to Porter.
 In 1944, the COE developed “House Document 494” which discussed a
Preliminary Examination and survey for flood control on the Chehalis
River and its tributaries.
 Between 1946 and 1949 the COE analyzed the concept of multiple
reservoirs on the Upper Chehalis River.
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 In 1965 the United States Bureau of Reclamation published the study
“Upper Chehalis River Basin Reconnaissance Report”.
 In March 1966, the COE conducted a localized evaluation of the flood
problems along Lum Road in Centralia and prepared a report “Coffee
Creek, Channel Excavation and Debris Removal under Section 208 of the
1954 Flood Control Act”.
 Between 1966 and 1971, the COE studied possible solutions to flood
damage occuring in the Aberdeen/Hoquiam/Cosmopolis region, Oakville
and Centralia/Chehalis region, and in rural areas along the Chehalis,
Skookumchuck, and Newaukum Rivers.
 In 1968 the COE published the document “Flood Plain Information –
Skookumchuck River, Bucoda, Washington”.
 In 1968 the COE published the document “Flood Plain Information –
Chehalis and Skookumchuck Rivers, Centralia-Chehalis, Washington”.
 In 1974 the COE produced the report “Special Study, Suggested
Hydraulic Floodway-Chehalis and Skookumchuck Rivers”.
 In 1974 the NRCS (previously the SCS) prepared a “Flood Hazard
Analysis for Salzer – Coal Creek”.
 In 1976 the COE published the report “Special Study – Suggested
Hydraulic Floodway, Chehalis and Newaukum Rivers”.
 In January 1977, the COE released “Chehalis River at South Aberdeen
and Cosmopolis, Washington – Final Environmental Impact Statement
(EIS) on Flood Control” for a proposed levee project.
 In March 1977 the NRCS (previously the SCS) prepared the “Flood
Hazard Analysis of China Creek”.
 In February 1978 the NRCS (previously the SCS) prepared the “Flood
Hazard Analysis of Coffee Creek”.
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 In December 1978, the FEMA produced the “Flood Insurance Study for
the City of Hoquiam, Washington, Grays Harbor County”.
 In March 1981, the FEMA produced the “Flood Insurance Study for the
Town of Bucoda, Washington, Thurston County”.
 In December 1981, the FEMA produced the “Flood Insurance Study for
the City of Centralia, Washington”.
 In 1982, the COE produced the report “Centralia, Washington, Flood
Damage Reduction Interim Feasibility Report and Environmental Impact
Statement”.
 In 1982, the COE produced an “Aberdeen-Hoquiam Flood Damage Plan
of Study”.
 In May 1982, the FEMA produced the “Flood Insurance Study, City of
Cosmopolis, Washington, Grays Harbor County”.
 In January 1984, the FEMA produced the “Flood Insurance Study, City
of Aberdeen, Washington, Grays Harbor County”.
 In August 1985, the FEMA produced the “Flood Insurance Study, City of
Elma, Washington, Grays Harbor County”.
 In 1988, the COE conducted an “Initial Reconnaissance Report on China
Creek at Centralia”.
 In May 1988, the COE completed a revised 35% level preliminary design
on a levee system for “Chehalis River at South Aberdeen and Cosmoplis,
Washington, General Design Memorandum”.
 In 1989, the COE investigated flood solutions to the flooding problem
centered on the Chehalis Avenuse Apartments in Chehalis.
 In 1990, the COE produced the report “Salzer Creek flood Damage
Reduction Report”.
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 In February 1990, the FEMA released the “Flood Insurance Study for
Grays Harbor County, Washington Unincorporated Areas”.
 In July 1990, the COE released the study “Chehalis River at South
Aberdeen and Cosmopolis, Washington – Flood Control Project – Final
Environmental Impact Statement (EIS) Supplement” for a proposed levee
project.
 In August 1990, the COE completed a reconnaissance report of the
January 1990 flood event “1990-Centralia-Chehalis Flood Warning and
Flood Response Study”.
 In 1991, the COE completed the following items for Centralia and
Chehalis: (1) a public brochure on what to do in a flood, (2) a flood
warning map, (3) a flood warning checklist for public officials on
facilities that may be flooded.
 In 1991, the FEMA Region X Interagency Hazard Mitigation Team
prepared the “Supplemental Flood Hazard Mitigation Report”.
 In May 1991, the COE released the “Flood Summary Chehalis River
Basin January 1990 Event and November 1990 Event Addendum”.
 In 1992, the COE produced the report “Skookumchuck Dam
Modification Project, Centralia, Washington”.
 In 1993, the COE developed a “Flood Phases Guidelines Manual that
includes the flood phase warning map for the Centralia-Chehalis valley.
 In 1999 the COE produced the report “Post Flood Study, Chehalis River
at Centralia, Lewis County, Washington.
 In June 1999, the FEMA issued a revised “Flood Insurance Study for
Thurston County, Washington Unicorporated Areas”.
 In June 2003, the COE published the report “Centralia Flood Damage
Reduction Project, Chehalis River, Final General Reevaluation Report”.
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 In June 2003, the COE also released the “Centralia Flood Damage
Reduction Project Chehalis River, Washington – General Reevaluation
Study – Final Environmental Impact Statement”.
 In July 2006, the FEMA released a revised “Flood Insurance Study for
Lewis County, Washington Unicorporated Areas”.
 In July 2006, the FEMA released a revised “Flood Insurance Study for
the City of Chehalis, Washington”.
 In March 2009, the “Comprehensive Flood Hazard Management Plan”
was prepared for the Confederated Tribes of the Chehalis Reservation by
GeoEngineers, Inc., and Herrera Environmental Consultants, Inc.
 In January 2010, the COE released “Wetland and Waters of the U.S.
Delineation, Rating, and Impact Assessment – Final Report - Chehalis
and Centralia Flood Damage Reduction Project Update Lewis County,
Washington” prepared by Tetra Tech, Inc.
 In November 2010, the FEMA released a “Preliminary (Revised) Flood
Insurance Study for Lewis County, Washington and Incorporated Aeas”.
 In May 2011, the COE released “Final Environmental Assessment –
Levee Rehabilitation – Skookumchuck River Levee, Lewis County,
Washington” for repairs to approximately 865 feet of exisiting levee
damaged during the December 2007 flood.
 (Not included in this list are numerous Design Memorandums, Reports,
Plans, Manuals, and Regulations developed by the COE for the
Wynoochee Dam.)
Existing Flood Control Works
The development of a list of existing flood control works proved to be a
difficult task despite the extensive list of previous studies. Basically there
have been a lot of studies, but apparently none have been sufficient to justify
the installation of federally cost-shared Flood Control Works, except for the
Wynoochee Dam.
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Existing flood control works are usually operated and maintained by a
Diking District or a Flood Control District.
Existing flood control works are usually operated and maintained by a
Diking District or a Flood Control District. Previously, Lewis County had at
least three flood control districts in the Chehalis Basin. These districts have
been dissolved in favor of having one all encompassing flood control district
which is called the Chehalis River Basin Flood Control Zone District.
Thurston County and Grays Harbor County have no diking districts or flood
control districts in the Chehalis Basin.
The following flood protection measures are listed in Flood Insurance
Studies that were prepared by FEMA for the Counties and Cities in the
Chehalis Basin.
Lewis County:
 There is approximately 1.75 miles of levee on the right bank of the
Chehalis River that protect the city-county airport from a 50-year
flood event at Chehalis.
 Channel realignment has been carried out on Salzer Creek from
River Mile 0.9 to RM 1.15.
 On the Skookumchuck River, left bank, 0.6 mile of levee protects
residential areas of Centralia, 0.2 mile of levee protects an
industrial area near RM 3, and 0.8 mile of levee has been built to
protect agricultural land near Bucoda.
 Repairs to existing levees for Salzer Creek and the Skookumchuck
River as a result of the 2007 flood were completed in 2009.
 The dam on the Skookumchuck River approximately 11 miles
northeast of Centralia provides the water supply for the coal-fired
steam electric generating plant, however, this dam does not
provide storage capacity necessary to significantly impact flood
flows downstream.
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 Other minor channel work and bank protection was carried out at
various sites on the Chehalis River, Newaukum River, North Fork
Newaukum River, and South Fork Newaukum River prior to 1986
by the USDA Soil Conservation Service (currently NRCS).
Thurston County:
 The Skookumchuck Dam discussed above, is actually located in
Thurston County, approximately 8 miles upstream of Bucoda.
 Several levees have been constructed on the Chehalis and
Skookumchuck Rivers, but none are adequate to provide protection
against a 100-year flood and are not shown on the Flood Insurance
Study maps.
 Riprap has been placed along the left river bank in the
Independence Road area which has had a negative impact on the
Chehalis Reservation.
 The NRCS installed a bank protection project on the right bank of
the Chehalis River near Grand Mound after the 1996 flood.
Grays Harbor County:
 Levees are located along the reach of the Chehalis River between
Montesano and Satsop; however, these levees are too low to
contain the 100-year flood.
 The Wynoochee Dam was completed in 1972 and has resulted in
reduced flooding downstream from the Wynoochee River. The
main purpose of the Wynoochee Dam is to provide industrial and
municipal water supply for the City of Aberdeen.
 The City of Aberdeen has a system of dikes along both banks of
the Chehalis River and Grays Harbor. These dikes will not protect
the city from the 100-year flood because the elevations of the tops
of the dikes are lower than the 100-year tidal elevation.
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 The City of Hoquiam is surrounded by levees. Portions of the
levee system were constructed originally by the COE in 1936. In
1973, a portion of the levee protecting East Hoquiam was repaired
by the COE as an emergency project. The remaining levee system
would probably not withstand a 100-year tidal flood.
 The City of Cosmopolis has a dike that was constructed in 1978 to
protect an area in northwestern Cosmopolis. This dike is
insufficient to protect the area from floods with return periods of
20 years or greater.
 NRCS has installed bank protection projects on the West Fork
Satsop River and the Wynoochee River.
Potential Flood Reduction Solutions
Table 13a shows a list of potential solutions to the existing flood problems,
such as represented in Figures 4 and 5 and Tables 7a and 7b. Some solutions
are likely to have opposition because of potential impacts on aquatic habitat,
especially salmonids. The bull trout, which has been listed as an endangered
species since 1999 (U.S. Fish and Wildlife Service, 2004), was listed to have
a Critical Habitat Designation in 2010 (USFWS, 2010).
Non-Structural
For approximately last 100 years, the methodology for attempting to control
flooding in the United States has been with structures: dams, levees, river
channelization, and drainage works. These flood control measures were a
large expense to the taxpayers, and often had the effect of luring unwise
encroachment into flood prone areas. This false sense of security was often
lost when large floods exceeded the design capacity of the structures. In the
Northwest, currently these solutions are likely to have opposition because of
potential impacts on aquatic habitat, especially salmonids.
In the late 1960’s, in an attempt to provide a new direction that would
emphasize other approaches to address flood problems, Congress initiated
the National Flood Insurance Program. This program was based on having
affordable flood insurance available in flood prone communities, and in
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return the communities would limit growth and development in hazardous
areas, and thus reduce the costs of flooding to all sectors.
In the decade of the 1990’s, with flood damages at an all-time high, and with
upwardly spiraling disaster relief costs that began to strain national budgets,
there were new approaches tried to reduce the damages associated with
floods in other parts of the country. The Midwest Flood of 1993 served to
be a catalyst to recognize the value and benefits of floodplains as natural
resources, and pointed the way toward restoration and wise management of
these beneficial resources as part of the overall strategy to reduce flood
losses.
In the wake of the 1993 Midwest Flood, many of the flooded communities
began to develop and implement a new strategy of voluntary buyouts and
relocations of homes out of flood plains. Since then, many other
communities across the country have followed suit. These actions represent
a major change in attitude and approach toward addressing flood problems,
with significant benefits to people at risk and taxpayers, as well as not
having adverse environmental impacts (Conrad, McNitt, and Stout, 1998).
The prime candidates for voluntary buyouts and relocations are properties
that are considered to be a “Repetitive Loss Property”. The National Flood
Insurance Program (NFIP) defines any insured property that has sustained
two or more flood losses in a 10-year period as a “Repetitive Loss Property”
(Conrad, McNitt, and Stout, 1998). In the time period between 1978 and
1995:
 Repetitive loss properties only represented two percent of the all
insured properties, but they claimed 40 percent of the NFIP
payments.
 Nearly one out of every ten repetitive loss properties has had
cumulative flood insurance claims that exceed the value of the
property.
A non-structural alternative to voluntary buyouts and relocation is flood
proofing existing structures. Flood proofing usually involves raising the
home or commercial building so that the first floor elevation is above the
base flood elevation.
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While structural flood control measures remain in the “study phase” in the
Chehalis Basin, the counties and cities within the basin have moved forward
with programs to flood proof and relocate flood prone structures.
Since 1993, the Cities of Centralia and Chehalis, Lewis County and
individual homeowners, with the support of FEMA, Washington State
Emergency Management Division, and the Small Business Administration
invested several million dollars to acquire or elevate many flood prone
residential structures in Lewis County (FEMA, 2008).
From 1994 to 2004 Lewis County, Centralia, and Chehalis combined flood
proofed 230 structures and removed 61 flood prone structures (Brown and
Caldwell, 2008).
To determine the effectiveness of this non-structural mitigation program,
FEMA, in 2008, developed a study on residential structures located in
Centralia that had been flood proofed. The study focused on 35 structures
that were elevated after the 1996 and 1997 flooding. Detailed flood
elevation data was obtained on these 35 structures following the December
2007 flood event. The total mitigation cost for the 35 structures was
estimated to be $1,017,000. Based on the December 2007 flood elevations,
the losses avoided were estimated to be $1,906,000. Thus the flood damages
prevented from a single flood event exceeded the project cost by almost 2 to
1 (FEMA, 2008).
In addition to the projects listed above, since 2006 Lewis County has
assisted in raising 105 homes within both the Chehalis and Cowlitz River
Basins. Also, Lewis County demolished 29 flooded homes after the
December 2007 flooding on the Chehalis River. Of the homes that were
damaged in the December 2007 event, 85% were not located in a mapped
flood zone.
The Chehalis Reservation is also reported to be currently implementing a
FEMA project to elevate and flood proof homes.
For livestock operations in rural areas, an effective flood proofing measure
that was developed in King County, Washington is critter pads. They have
also been used in Tillamook, Oregon. These are areas of fill placed above
the estimated flood elevations where livestock and equipment can be placed
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during flood events. There is a high potential for adding this agricultural
flood proofing to flood prone areas in the Chehalis Basin.
Some of the solutions such as flood proofing that were so effective in the
Centralia area during the 2007 flood can be done with essentially no off-site
stream effects.
Instream Measures
Other in-stream solutions such as sloping back high stream banks to increase
flood plain capacity, or bar scalping of gravels to reduce stream bank erosion
must be done in an environmentally sensitive way to minimize off-site
effects (Reckendorf, 2006). The same is true of streambank erosion
treatment to reduce sedimentation into rivers that reduces stream capacity.
However, this work to reduce the damaging impacts of flooding can be done
in a way to enhance aquatic and riparian habitat.
Missing Data
There is no comprehensive landscape geomorphic analysis of the multiple
geomorphic surfaces with difference in flooding and drainage that exist
along the Chehalis River. Figure 18 shows two different geomorphic
surfaces that would flood with a different frequency. Figure 18 is similar to
Figure 10 block diagram showing differences in soils. A check with the soil
survey map along Highway 6 shows that the lower geomorphic surface in
Figure 18 has Newberg and Cloquato Soils and the higher geomorphic
surface has Chehalis soil.
A study of the multiple geomorphic surfaces is needed to separate those
lands that could be readily be used for cropland agriculture as opposed to
those that should only be used for pasture. Such a study could also establish
the most appropriate part of the floodplain for placement of critter pads, to
get stock and equipment above oncoming flood waters. With the stage
discharge curves like shown in Figure 4, regional and local flood forecasters
will predict expected flood stage. With this information, local landowners
could determine whether the projected stage will flood their ground. In
other words, should they implement placement of their flood proofing gates,
or move stock and equipment up to the higher pad levels. The need is to
establish the correlation of stream gage stage to the expected elevation at the
place of flood proofing or critter pad.
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This also emphasizes the need to maintain the current stream gage network.
Table 6b lists the stream gages in the Chehalis Basin that have been
discontinued, and are no longer available to provide flood discharge and
stage information.
We found no study of the landscape geomorphology of the Chehalis Basin
since Bretz did his work in 1913, which is over 100 years ago. Cities have
expanded into wet areas that were Pleistocene Lakes without reflecting the
geologic and geomorphic history that these areas had an extremely high
flood hazard. An updated study of the landscape geomorphology might
reveal solutions such as potential channel bypass areas to offset the impacts
of development in such a hazardous flood area. The landscape analysis
would help in understanding the recharge of streams by inter-flow, and
where streams are losing flow. The landscape geomorphology would be a
reflection of the depositional history during the Pleistocene to recent time.
To further understand the depositional history, the surface analysis could be
tied to the stratigraphy data from hundreds of new wells placed in the basin
in the last 100 years. The well data would help in understanding the
unconfined aquifers, and their role in the gaining and losing streams. This is
important from both a water quality perspective, as well as for low flow for
salmonids.
Accelerated Soil Erosion Reduction
Upland
There is an overall lack of information about upland overland erosion,
especially for soil creep. This is a known problem for upland erosion in the
Satsop Watershed but there has been no evaluation on any other watershed.
This may be partly an elevation problem, and freeze-thaw conditions for
upland slopes coming off the Olympic Mountains, but even that is
speculative, and needs a specific study of cause and effect on upland
watersheds (Weyerhaeuser Company and Simpson Timber Company, 1996).
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Landslides and Debris Flows
There have been only four studies completed under the LHZ project, and
only eight watershed analyses. Some of the watersheds producing the
highest measured suspended load sediment yield like upper Skookumchuck,
upper Wynoochee, and upper Newaukum, have had studies but more work is
needed.
For example the stair step profile of the Newaukum River shown in Figure
3d reflects an unstable stream that is downcutting in Stage II of the Channel
Evolution Model (Natural Resource Conservation Service, 2007). This
profile relationship needs field follow up to determine if local headcuts are
being initiated or are just headcuts on the main stem Chehalis working their
way upstream. If with field investigation the downcutting and headcuts are
established, the downcutting process needs to be further evaluated for what
hillside landscapes are being undercut, and the rate of headcut migration.
This applies to the entire upland subwatershed. An initial step would be to
determine a stream profile for these upland watersheds. High resolution
LiDAR, with some local elevation controls could expedite profile surveys of
the upland streams with a history of side hill landscape landslides as
opposed to road fill landslides and debris flows.
The road related cut and fill landslides need an expedited survey as part of
the LHZ Project. Both the natural slope and road landslides and debris flows
contribute substantial quantities of sediment loads. These sediment loads
smother spawning areas and or cause sediment intrusion into spawning
gravels. This has the effect to reduce dissolved oxygen around the spawned
eggs, to lethal levels.
There is also a data gap on an overall inventory of landslides in the basin,
whether or not streams have a known high sediment load problem. Even the
sub-basin with watershed analysis, some of which are 16 years old should be
re-evaluated. This could be done by using the latest LiDAR flights and or
possible comparing the flights for different years.
Reckendorf (2008a; 2008b), and Benda and Dunne (1997a; 1997b) have
pointed out landslides and debris flows provide coarse material that partially
blocks stream channels and the rivers find it easier to erode the streambanks
than to move the coarse material of the landslide or debris flow. These large
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coarse deposits get reworked downstream in the large subsequent flood
events, and at every new location of deposition, those streambanks get
eroded back. There is a need to study this debris flow movement
phenomenon in the future after a large storm creates landslides and debris
flow. In addition, there is a need to study the rainfall distribution and
intensity using radar, to determine if storms stall over specific watersheds. It
would also be desirable to study LiDAR post landslide events to locate both
landslides under the trees, and deposition areas as fans along the channel.
Any fan produced when a landslide or debris flow enters a channel would
cause the stream to erode around the deposit, and to erode out the opposite
streambank. This has been observed by Reckendorf (2008a)
Accelerated Streambank Erosion
Streambank erosion has been documented in the Chehalis Basin for many
years. Figures 13 through 20 show an aerial photo comparison of seven sites
between 2006 and 2009. As shown for each site, there is a streambank loss
that varies from 16.8 feet to 87 feet at the sample areas for the 2007 flood.
Table 12 is a companion document that shows the volume in tons of soil
eroded from each site. Most streambank loss tends to occur during the
falling stage of flood events (Reckendorf, 2010). During the falling stage
some flood water returns to the channel by flowing across the flood plain to
the channel. However, as the flood stage drops the water continues to flow
back into the channel by inter-flow (lateral seepage). Water in low areas on
the flood plain will not return to the river as overland flow but will seep
down to layers in the soil with higher hydraulic conductivity. Therefore,
there is created a head differential between the water on the flood plain that
seeps downward and laterally to that flowing out of the streambank. This
hydraulic differential creates seepage forces in the streambank that both
wash fines and sands out of gravel layers, creating a stratigraphy overhang,
which fails. The seepage forces also reduce the volume weight of the
cohesive soils to their buoyant unit weight, which makes mass rotational or
lateral failure easier. (Reckendorf, 2010). The cohesive soils develop
during the falling stage of the flood a higher pore pressure, which weakens
the soil strength so it can more easily fail.
The losses shown in Table 12 are above an average streambank loss
condition, because the 2007 flood was such a large flood event. However,
the 2007 event effects need to be taken into consideration as increasing flood
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damages, because of the large sediment volume that entered the river at the
sample sites. A total of 91,541 tons of sediment entered the rivers at the
sample sites. Figure 12 is just a start at identifying streambank erosion areas
along streams in the Chehalis Basin. A basin wide study of streambank
erosion is needed.
To get a better perspective on streambank erosion after the 2007 flood, that
is closer to an annual rate, there is a need for a study of new riparian
plantings. It can be determined how far the river has encroached into the
plantings, so an erosion rate since planting can be calculated.
Another need is to do an evaluation of streambank erosion changes over
time, using LiDAR flights. The LiDAR coverage varies by counties, so a
priority for evaluation of streambank erosion using LiDAR needs to be
established.
The causes of the existing streambank erosion in the Chehalis Basin should
also be studied, if one wants to know the solutions with the most potential to
bring streambank erosion back to some background rate of loss. In addition,
an understanding of the causes will help develop solutions for streambank
erosion that are compatible with aquatic habitat. In other words, the same
treatment to reduce the streambank erosion, will enhance aquatic habitat.
The study by Reckendorf (2010) titled, “Streambank Erosion Causes, and
Large Woody Material Solutions for Streambank Erosion and Sediment
Reduction,” provides a starting point to help in such an evaluation.
Sedimentation Impacts
As stated, there is only one specific study of sediment transport in the
Chehalis Basin. This is the USGS study by Glancy (1971), Sediment
Transport by Streams in the Chehalis River Basin, Washington, October
1961 to September 1965. This study of suspended sediment load measured
sediment at 19 different locations. Annual sediment loads varied from
270,000 tons to 690,000 tons. About 74% of the sediment yield was derived
from the Satsop and Wynoochee Rivers.
The East and West Forks of the Humptulips River have been shown to have
a chronic sediment supply problem that relates to its small episodic peaks of
increased sediment supply in response to limited natural disturbances. The
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chronic sediment supply is principally derived from the evacuation of glacial
valley fill during each peak flow event that has caused localized
undercutting. Road erosion also has a low to high designation based on the
area in the watershed (Lingley, Diem, Schelmerdin, 2003). The Humptulips
River was not a stream included in the suspended sediment evaluation of
Glancy (1971), so a characterization of the suspended load from the noted
flood events is an unknown and constitutes a data gap.
There is a need for specific studies of erosion conditions producing
downstream sediment in specific watersheds. Certainly the Satsop,
Wynoochee, Chehalis River above Doty, and Newaukum Rivers would be
priority rivers to better understand upland (especially landslide) erosion,
sheet and rill erosion, soil creep, and streambank erosion. These studies
should establish a delivery ratio for sedimentation, based on the erosion
determined.
The streambank eroded sites like shown in the eight site examples in Table
12, provide stream sediment that would have a substantial impact on
spawning and rearing. Pools would be substantially filled, so there would be
a lack of deep pools for holding areas. This is particularly critical because
the sparse riparian vegetation provides minimal overhead cover to reduce
stream temperatures, so shallow pools would have elevated water
temperatures. The other impact is that the high sediment load from the
failure of the stream banks will both bury spawning areas, and cause
sediment intrusion into spawning areas, and have associated impacts as
described under the landslide sediment impact.
The streams after the 2007 flood have become wide and shallow rather than
narrow and deep as would be desired for this stream type, to develop good
fish habitat. This results in a condition having developed because of poor
sediment transport. Therefore, there is need for a streambank erosion and
associated sediment yield study in the Chehalis Basin. This study could be
part of an overall fluvial geomorphic study of the basin. The associated
fluvial geomorphic evaluation could determine how to make the existing
streams do four things: (1) provide a condition for efficient sediment
transport; (2) provide a condition of pool and riffle habitat with submerged
wood; (3) provide overhead riparian cover for shade for salmonids, that does
not erode and fall into the river; and (4) provide streambank protection for
the streambanks, using the solutions provided to obtain the improved habitat.
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This can be done as a win-win solution for both the salmonid habitat, and for
the landowners.
The Anchor QEA, LLC.(2012) analysis or any of the studies they refer to
did not consider the possible negative impacts from sedimentation in the side
channels, if side channels are opened up for flow through access by
salmonids. It appears that the Tier 1 projects intend to open up side channels
along the incised channels, but there is no evaluation of the potential impacts
of creating avulsions that cause the abandonment or modification of the
main stem pool/riffle habitat and spawning and rearing areas. In addition,
there is no evaluation that potential avulsions could bury spawning and
rearing areas downstream resulting in a major negative impact of directing
flow to off channel old stream channels. Such impacts have been described
in Reckendorf (2010). In addition, loss of created side channel habitat due
to sedimentation has been described by the Southerland and Reckendorf
(2010) study but is not covered in the Anchor QEA, LLC.(2012) report. It is
also not stated in the Anchor QEA, LLC. (2012) study how much off
channel habitat in old channels will be accessed from the bottom end as
alcoves, as opposed to flow through side channel habitat. No discussion was
given in the Anchor QEA, LLC. (2012) report as to how deep to dig the side
channel habitat to make that habitat successful as off channel rearing areas.
In addition, the amount of wood needed for submerged cover was not
included in the Anchor QEA, LLC. (2012) report, or the amount of overhead
cover that would need to be provided to reduce potential high temperature
water in created side channels. There is also a negative potential impact of
downstream sedimentation to pool and riffle habitat, below culverts that are
improved for fish passage, that is not reflected in the Anchor QEA, LLC.
(2012) analysis. This report is currently in draft form so some of the above
issues may be addressed in the final document.
In western Washington, some off-channel projects designed to connect old
stream channels to a main stem have developed sediment problems. The
primary sediment problem is deposition that prevents side channel use for
summer refugia, because the channel is too shallow with too much sediment
to allow needed salmonid access. In addition, some main stem habitat
projects have become isolated because the stream has changed channels.
Sedimentation in the former main stem channels prevents access for
salmonids to these former channels during the summer months. There is a
need to evaluate all existing and proposed side channel habitat projects in
the Chehalis Basin to determine if there is a fluvial geomorphic favored
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solution that allows side channel habitat to remain open once constructed, or
to reopen side channel habitat that has filled with sediment.
Estuary
Grays Harbor’s filling history in the last 9,000 yrs, shows that there is
probably more sediment supplied from the Chehalis Basin than can be stored
in Grays Harbor. The conclusion by Peterson and Phipps (1992) was that
there was substantial sand bypass in late Holocene time. The COE has a
challenge to continue to dredge what sediment is deposited, and where in the
ocean to dispose of the excavated sediment. They should continue to
explore the pipeline land disposal if they can find suitable sites.
Fluvial Geomorphology Needs
There is minimal existing data that would help one understand the fluvial
geomorphology of the Chehalis River. Traditional cross sections taken for
FEMA studies do not survey in enough detail to determine the plan form
characteristics like pools and riffles, or breaks in side slopes that might
represent bank flow effects. The WDFW may have some detailed studies of
stream planform, channel slope and channel cross sections but that
information was not obtained as part of this study. If such information does
exist it should be analyzed before any fluvial geomorphic study is started.
Basic data is needed on cross sections or stream profiles that can be used to
determine: (1) Flood Plain Dimension; (2) Stream Dimension (width and
depth); (3) Stream Pattern; (4) Slope; and (5) Bed Material Class. In
addition, there is no data in the basin on channel evolution to determine if
any given reach is downcutting or widening, and no comprehensive analysis
of stream planform type. Traditional cross sections taken for FEMA studies
do not survey in enough detail to determine the plan form characteristics like
pools and riffles, or breaks in side slopes that might represent bank flow
effects.
To do a proper Rosgen Stream Classification there is a need for stream
cross-sections, and long profile for each reach evaluated. In addition, there
is a need to classify the streams stage as classified in the Channel Evolution
Model (NRCS, 2007) to determine the trend in terms of down-cutting and
widening. To represent the stream profile, the stream planform type
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(cascade, step-poll, pool-riffle, or dune-riffle) should be a part of the fluvial
geomorphic study.
A Rosgen Stream Classification of any given stream reach in combination
with the Channel Evolution Model, (NRCS, 2007) is needed to determine a
rivers trends in terms of downcutting and widening, along with a
determination of the bed material pattern by a system like the planform
characteristics given by Montgomery and Buffington (1997a). These will
provide most of the essential information needed to do stream work of any
kind. The primary missing components that must be added for a
comprehensive physical stream evaluation are bankfull flow depth and
discharge, peak flows, an evaluation of the streambank erosion and its
causes, as well as riparian vegetation. Other important stream physical data
like overhead cover and submerged cover, should also be determined as part
of an aquatic habitat analysis.
Having the appropriate fluvial geomorphic information will allow for
successfully developed solutions that will maintain needed off-channel
aquatic habitat that maintains an open channel for summer refugia.
A comprehensive fluvial geomorphic evaluation will allow any activity
along the river and its associated flood plain such as in channel or
streambank habitat restoration, side channel habitat created, riparian
planting, large woody material removal or placement, riprap, drop
structures, levees, sedimentation, dredging, gravel removal, and flooding to
be placed in perspective with respect to cause and effect.
Ideally, to proceed with effective long term local stream reach restoration,
no future work along the streams in the Chehalis Basin would proceed
without a comprehensive fluvial geomorphic analysis such as described
above. In addition, if one wants to achieve long term stability of any given
entire stream, it is desirable to do a natural channel design, using the
Watershed Assessment of River Stability and Sediment Supply (Rosgen,
2012) to design a salmonid habitat improvement and passage project. Use of
RIVERMORPH software to achieve a natural channel design is desirable.
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Drainage
The needs for additional drainage are unknown, for any land use. Any
additional attempt at drainage on agricultural lands or urban lands has an
extensive list of regulatory requirements that would likely preclude any type
of economic solution.
Ground Water
As stated in the Tetra Tech/KCM and Triangle Associates (2004) ground
water information is inadequate for resource management purposes. Some
detailed studies have been done but it is not known how representative the
results of these studies are for the entire basin. Specifically the following
areas of uncertainty affect implementation of the Chehalis Basin Plan:
-Are there aquifers that have not been previously identified and/or explored?
-How closely are ground and surface water connected?
-Where they are closely connected, are travel times long enough that ground
water withdraws could be timed to lessen the impact on surface water
bodies?
-Does the interaction between surface and ground water cause water to flow
from the surface to ground water or from ground water to surface water, and
does it vary throughout the basin, and or throughout the year?
-True legal appropriation of water rights. There are approximately 8,500
water rights claims in the Chehalis Basin. Almost nothing is known whether
these claims are valid and actually being used.
-The number of exempt wells was estimated as part of the CBP Watershed
Plan. The number of exempt wells used for industrial water and stock water
or quantity of water consumed is not known.
Water Quality
As stated in Tetra Tech/KCM and Triangle Associates (2004) while much
work related to water quality has been done, there is no coordinated
systematic planning, monitoring and reporting that has been established.
Because of this many sampling programs are not widely known.
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Observations throughout the study by Green, Loft, and Lehr (2009) have led
to a series of recommendations to improved water quality and water quantity
monitoring in the Chehalis Basin:
1) Develop community-based water quality goals based to improve
specific water quality parameters based on present water quality
status.
2) Investigate the possibility of utilizing the Enterococcus endpoint
instead of fecal coliform to evaluate tidally influenced sites.
3) Identify the presence and magnitude of variations in water quality
between monthly sampling events. This variation could be assessed
using data collected with long-term deployment monitoring probes
currently operated by the Chehalis Tribal Department of Natural
Resources.
4) Identify quantitative relationships between land use, Best
Management Practices to reduce water pollution, and water quality.
5) With the aid of the information provided in this report, develop
reach-specific restoration and preservation priorities that target
priority water quality parameters.
As stated in Collyard, and Von Prause (2010). Many water cleanup
activities have occurred in the Upper Chehalis River basin (WRIA 23).
However, there needs to be an additional effort to track and summarize these
activities in a comprehensive and detailed manner. Although most cleanup
efforts have been tracked individually, the details provided have often been
insufficient. Detailed information is needed to determine the effectiveness of
cleanup efforts and their associated impacts on water quality improvements.
This will help guide future cleanup and watershed management efforts.
Based on Washington State water quality standards and trend analysis, fecal
coliform concentrations within WRIA 23 have been reduced significantly.
Also, water quality management efforts within WRIA 23 appear to be
sufficient in preventing additional fecal coliform violations as long as the
efforts are sustained. However, additional monitoring needs to occur to
determine if target limits identified within the TMDL are being met.
No given BMP or water cleanup activity can be attributed to the reductions
in fecal coliform at TMDL target stations monitored in the CBP study. The
reductions likely came from a combination of early efforts involving (1)
updates of wastewater treatment facilities in Chehalis (2007) and Centralia
82
(2004), (2) updates and loss of large dairy operations in the watershed, and
(3) individual BMP’s.
Temperature and dissolved oxygen violations continue to be problematic
throughout WRIA 23. Based on single-sample temperature and dissolved
oxygen measurements, additional stream reaches would be listed as impaired
on Washington’s 303(d) list. Problems with dissolved oxygen results from
the CBP study do not allow this data to be used to identify impairments for
this purpose.
Trend results from Ecology’s long-term ambient monitoring stations at
Porter and Dryad suggest little change has occurred in dissolved oxygen
concentrations over time. Neither of the small increases in dissolved oxygen
at Dryad or Porter were statistically significant based on regression tests.
Seasonal Kendall tests are consistent with regression results, although no
change was detected based on the slope.
Based on trend analysis, turbidity does not appear to have increased over
time. However, the variability of turbidity measurements and the influencing
factors reduce the power of this type of trend analysis. Trends or patterns in
turbidity may exist but may require additional, more complex data analysis
or a larger data set. Multiple-linear regression (MLR) could be helpful in this
effort. MLR could account for the influence of outside parameters such as
precipitation, streamflow, and time to produce better trend results. MLR
could also link water quality with land use using geographic information
systems (GIS).
The recommendations in Collyard, and Von Prause (2010) are:
• Begin to inventory implementation of BMP practices throughout
the Upper Chehalis River basin (WRIA 23) in a comprehensive
way using the following questions as a guide:
1. Describe in detail the BMP being implemented and how it is
expected to improve water quality in the Chehalis River
watershed.
2. Is the BMP sustainable?
3. When and where was the BMP implemented?
4. What is the spatial extent of the BMP?
• Monitor fecal coliform at TMDL target stations not sampled by
the CBP and compare results to TMDL target limits.
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• Monitor fecal coliform at stations and critical periods identified
in the TMDL.
• Use the LCCD’s riparian assessment maps to implement BMP’s
on impaired stream reaches with low buffer percentages.
• Use and explore the numerous past assessment efforts to guide
new BMP implementation efforts in the watershed.
• Assess percent shade at target stations identified within the Upper
Chehalis Temperature TMDL to track progress for this long-term
goal.
Continue to explore data from WRIA 23 using appropriate
statistical techniques, such as MLR, to better detect long-term
trends. •Also explore techniques for linking land use and other
activities with water quality data.
• Consider monitoring temperature using continuous temperature
loggers at stations with the highest number of temperature
violations.
• Assess land use using ground sleuthing and GIS in surrounding
areas where dissolved oxygen continues to be a problem. Based
on this approach, design a monitoring strategy in areas that have
the greatest risk to negatively affect dissolved oxygen and where
low dissolved oxygen values are observed.
• Consider monitoring dissolved oxygen using continuous loggers
at stations with the greatest number of violations. Also,
periodically supplement dissolved oxygen data during critical
periods with ammonia, carbonaceous biochemical oxygen
demand, and streamflow data to determine what is driving low
dissolved oxygen levels.
• Use a source tracking component in all future water quality
sampling designs to help define major pollutant sources when
water quality violations are identified.
• Consider using instream biological and habitat methodologies in
the upper reaches of WRIA 23 to address fine sediment concerns
• Continue to support ambient monitoring efforts in the Chehalis
River watershed and consider the reactivation of some of
Ecology’s ambient monitoring stations within the basin.
• Once TMDL compliance stations and critical periods are
determined to be meeting targets, change the fixed-station,
WRIA-wide sampling strategy to a probability (random)-based
sampling design to monitor the status and trends of fecal coliform
84
concentrations. Sampling should be conducted every 3-5 years
and should follow probability survey designs outlined by EPA.
Aquatic Habitat
As stated in Tetra Tech/KCM Triangle and Associates (2004) fish use and
habitat conditions have not been well documented in the Elk River, Johns
River, Newskah Creek, Charley Creek, Hoquiam River, and Wishkah River.
These streams need studies on fish use and habitat. In addition, very little
data exists about specific flow requirements for fish in sub-basins
throughout the watershed. This also is recommended. Any evaluation for
flood damage reduction on any of these streams is likely to run into
considerable opposition unless aquatic, wetland, and riparian habitat studies
on these streams are completed.
Current stream and watershed conditions limit aquatic habitat. Limiting
factors as shown in Anchor QEA, LLC (2012) for salmonids include fish
blockages (impassible culverts), flood plain condition (incised channels,
drainage, or filling of wetlands), streambed substrate (mass wasting or low
woody debris), riparian condition (tree canopy), water quality (high water
temperatures or low dissolved oxygen), and water quantity (low summer
base flows). To these could be added several physical characteristics: flood
plains disconnected from channel by dikes, flood plain old channels not
connected to stream, accelerated streambank erosion causing excessive
sedimentation, inadequate pool and riffle planform characteristics,
inadequate submerged LWD and stream channels that are too wide and
shallow to transport their sediment load.
Anchor QEA, LLC(2012) has identified several potential problem categories
as follows:
• Fish Passage Conditions: Poor fish passage conditions typically
result from improperly sized water crossing structures and result
in loss of access to spawning and rearing habitat.
• Floodplain Conditions: Degraded floodplain conditions typically
result from floodplain filling, dike and levee construction, and
streambank armoring and result in loss of backwater and side
channels used for spawning, rearing, and refugia during high
flows.
85
• Riparian Conditions: Poor riparian conditions typically result
from intentional removal of vegetation, usually associated with
land use conversion or timber harvest, and results in limiting
shade, nutrients, and large woody debris availability.
• Large Woody Debris: Lack of LWD usually results from poor
riparian conditions and removal of woody debris from the
channel.
• Water Quality: Poor water quality typically is associated with
water temperature, suspended solids, and chemical composition
usually resulting from poor riparian conditions and stormwater
runoff problems.
• Water Quantity: Low summer flows typically result from altered
hydrology (landscape changes that allows rapid surface runoff).
• Streambed Sediment: High contributions of sediment typically
are associated with land use management practices including
logging roads, landscapes without vegetation, and areas of
excessive streambank erosion resulting in filling in of pools and
spawning gravels.
The Anchor QEA, LLC(2012) report prioritized projects that would be most
beneficial. They include reconnection of isolated habitats, replace culverts
for fish passage and access to additional habitats, restoring flood plain
connection, restoring LWD, and restoring riparian habitat. These factors
were considered (Anchor QEA, LLC,2012) as Tier 1 potential projects.
Anchor QEA, LLC also prioritized the degree of impact of each limiting
factor in Tier 1, on the fitness and survival of targeted stocks. Anchor QEA,
LLC (2012) list potential projects for Tier 1 limiting factors and fish passage
barriers that were ranked.
The LCCD along with the MCD (2007) completed a joint project to rank
barrier culverts for replacement. The top 99 culverts identified by LCCD are
included in the Anchor QEA, LLC (2012) report. Based on relative
elevation maps and an analysis of aerial photographs, Anchor QEA, LLC
(2012) shows for the Skookumchuck and South Fork Chehalis potential
restoration of flood plain, off channel, and side channel habitats. However,
the AnchorQEA, LLC (2012) study is missing the information on current
land use and ownership, to determine if restoration in those specific areas is
feasible. In addition, their Tier 1 analysis of flood plain and riparian areas
covers only a sample of the streams (Skookumchuck and South Fork
86
Chehalis) in the Upper Chehalis (WRIA 23), and there is no equivalent Tier
1 type analysis for the Lower Chehalis (WRIA 22).
Wetlands
As stated in Tetra Tech/KCM and Triangle Associates(2004) a
comprehensive survey of potential wetlands restoration sites has not been
done basinwide. Such a survey needs to include viable projects and pilot
studies to evaluate the impact of wetland restoration activities, that would
benefit all environmental elements of the basin.
CONCLUSION
Efforts to reduce flood damages in the Chehalis Basin is intertwined with the
need to reduce erosion on the uplands, especially from the landslides and
streambank erosion in the uplands and lowlands. Streambank erosion
especially during floods, cause a loss of riparian and wetland habitat, and
these losses are substantial during a large flood like that which occurred in
2007. The landslide and streambank erosion is then intertwined with the
sediment in the channel and reduces channel capacity, causes smothering of
spawning areas, sediment intrusion into spawning areas, and filling holding
pools for salmonids. The riparian loss from floods and other causes has
resulted on high stream temperatures, because of the loss of overhead cover.
In spite of the hundreds of studies that have been done in the Chehalis Basin
in the lowland flood plain streams, there is little baseline data collected on
the appropriate fluvial geomorphic parameters. That should be studied
before any work is done along a stream. It was established long ago by
Leopold, Wolman, and Miller (1964) that the controlling factors in
development of a river are depth, width, slope, velocity, discharge, size of
sediment and roughness of the stream channel. He later established that
bankfull was the appropriate discharge to use in the evaluation.
Rosgen developed his stream classification system based on bankfull flow
characteristics, so if one collects the essential data to classify any given
stream reach by the Rosgen system they will have collected most of the
essential information needed for an adequate fluvial geomorphic evaluation.
In addition, to classify streams using the Rosgen System (Figure 8a) it is
recommended that the stream be also classified using the Channel Evolution
87
Model (Figure 8b) to determine if the stream is downcutting, widening, or
in a stable state. It is also recommended that the stream reaches in the
Chehalis Basin be classified by planform characteristics in the Montgomery
and Buffington (Figure 9) system. Some stream reaches do have some
limited classification presently as pool/riffle, step/pool or cascade, but
overall the planform characteristics of most stream reaches are unknown.
Other important physical data like streambank erosion causes, riparian
cover, and specific overhead and submerged cover is needed in any reach
under evaluation.
Having the appropriate fluvial geomorphic information will allow for
successfully developed solutions that will maintain needed off-channel
aquatic habitat that maintains an open channel for summer refugia. In
collecting the appropriate fluvial geomorphic investigation along any given
stream reach and its associated flood plain, one can make informed decisions
on streambank habitat restoration, side channel habitat, riparian planting,
large woody material placement or removal, riprap, drop structures, levees,
placement or removal, sedimentation impacts or any removal, and flooding
in perspective of cause and effect.
There is little evidence we could find of a comprehensive landscape
geomorphic analysis of the multiple geomorphic surfaces present along the
streams in the Chehalis Basin to distinguish differences in flood hazard for
any given piece of flood plain. A study of the multiple geomorphic surfaces
is needed to separate those lands that could be readily used for cropland
agriculture (because they flood less frequently and with less depth), as
opposed to pasture. Such a study could establish the most appropriate part
of the flood plain for placement of critter pads for stock and equipment. The
appropriate hydrology would establish flood depth. There is also no recent
landscape geomorphic study to update Bretz’s 1913 study to current
conditions. Such a study might help to establish flood reduction conditions
based on the geomorphology of the landscape, and the stratigraphy of the
subsurface Pleistocene glacial deposits.
A list of the potential solutions to flooding problems in the Chehalis Basin is
shown in Table 13a. Some of the solutions such as flood proofing that were
so effective in the Centralia area during the 2007 flood can be done with
essentially no off-site stream effects. Funding to enhance the flood proofing
in other communities is needed. Solutions like eliminating the restrictions
along waterways require both small and large units of government to make
88
long term commitments to those types of solutions so that they can acquire
the needed funding for such efforts. Other in-stream solutions such as
sloping back high streambanks to increase flood plain capacity, or bar
scalping of gravels to reduce streambank erosion must be done in an
environmentally sensitive way to minimize off-site effects (Reckendorf,
2006). The same is true of streambank erosion treatment to reduce
sedimentation into the river that reduces stream capacity. However, this
work to reduce the damaging impacts of flooding can be done in a way to
enhance aquatic and riparian habitat. Establishing critter pads for livestock
and equipment likely needs state or federal cost sharing as this would be a
new practice in the Chehalis Basin, and likely will be adopted slowly.
Increasing stream bank protection, which is an established USDA cost
shared practice, will likely need a different type of evaluation to show that a
fluvial geomorphic evaluation with a large wood solution can be compatible
with stream fish habitat. The high stream temperatures during the summer
months need to be addressed by a comprehensive riparian management
program. Therefore, any work done for flood control or streambank erosion
control, will have the beneficial effects of the lower stream temperatures
afforded by the riparian planting effort.
Results from the State of the River Report (Green, Loft, and Lehr, 2009)
suggest there is a wide range of water quality conditions in the Chehalis
Basin, ranging from relatively undisturbed to severely degraded. This
conclusion is consistent with previous water quality studies within the Basin.
This study also suggests that the determination of water quality health is to
some extent dependent on the specific standard used.
SCOPE OF FUTURE WORK
Based on the 22 categories of potential structural and non-structural flood
damage reduction needs shown in Table 13a, there are tremendous long term
needs in the Chehalis Basin. Before projects in many of these categories can
be implemented there is a need for studies to fill the gap in our
understanding of the resources mentioned. Table 13b is a current list of 19
specific studies proposed.
After LCCD makes the Chehalis Basin study available, they can prioritize
studies and have staff determine a representative sample area. Part of that
determination depends on whether LCCD should take the leadership on the
89
studies that are basin wide or only focus on Lewis County. In other words,
let each conservation district focus on the critical study needs in their
respective counties.
Assuming LCCD takes basin leadership then the scope of work sequence is
as follows:
1. Prioritize studies from Table 13b.
2. Determine roughly a 40% sample area to represent the study resource
problem.
3. Determine the time necessary to complete the 40% sample.
4. Determine the personnel to complete the 40% sample.
5. Determine the training needed to accomplish the study and cost of
training.
6. Figure out a methodology to project the results of the 40% sample to
the whole basin.
7. Plan to prepare individual maps and reports that support the results of
each study.
8. Prepare a cost estimate for each individual study on the priority list.
9. Seek grants as appropriate to support staff to complete each
individual or combination of studies.
10. Determine generic request for proposals that could be used for any
study in Table 13b, which could be used by any conservation district
or other unit of government to pick off the specific studies they
wanted done in their county.
90
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