FLOOD ATTENUATION PROPERTIES OF A SIERRA NEVADA ALPINE
MEADOW
Lauren Amanda Mancuso
B.A., University of California, Davis, 2006
THESIS
Submitted in partial satisfaction of
the requirements for the degree of
MASTER OF SCIENCE
in
GEOLOGY
at
CALIFORNIA STATE UNIVERSITY, SACRAMENTO
SUMMER
2011
FLOOD ATTENUATION PROPERTIES OF A SIERRA NEVADA ALPINE
MEADOW
A Thesis
By
Lauren Amanda Mancuso
Approved by:
__________________________________, Committee Chair
Kevin C. Cornwell, Ph.D.
__________________________________, Second Reader
Timothy Horner, Ph.D.
____________________________
Date
ii
Student: Lauren Amanda Mancuso
I certify that this student has met the requirements for format contained in the University
format manual, and that this thesis is suitable for shelving in the Library and credit is to
be awarded for the thesis.
______________________, Department Chair
David G. Evans, Ph.D.
Department of Geology
iii
___________________
Date
Abstract
of
FLOOD ATTENUATION PROPERTIES OF A SIERRA NEVADA ALPINE
MEADOW
by
Lauren Amanda Mancuso
The purpose of this study is to assess how meadows aid in flood attenuation and
groundwater storage of the Van Vleck meadow in the Sierra Nevada Mountain Range. A
water budget for the meadow was developed to understand the quantity and timing of
water entering and leaving the meadow throughout the 2009-2010 water year. The water
budget was developed by tracking the quantity of water entering and exiting the
meadow. The water storage capacity was estimated based on the data collected for the
water budget in addition to other field studies. Flood attenuation parameters were
assessed by comparing the trend of water quantities increasing and decreasing during the
study period based on the amount of water entering and exiting from surface water
locations. Results suggest that the meadow does aid in flood attenuation and may lessen
iv
the severity of the dry season downstream. Based on the water budget values, the results
suggest the water in the meadow is potentially recharging aquifers via bedrock fractures.
The results of this study will assist in informing the U.S. Forest Service and Department
of Water Resources regarding the usefulness of healthy meadows as an alternative to
building dams and reservoirs for storing water.
_______________________, Committee Chair
Kevin C. Cornwell, Ph.D.
_______________________
Date
v
DEDICATION
This thesis is dedicated to my grandmother, whose value of hard work inspires me.
vi
ACKNOWLEDGMENTS
I am greatly appreciative to my parents, Sandra and Lawrence Mancuso, for their long
hours spent assisting with fieldwork. I thank my brother, Nino Mancuso, for his input
with the preparation of this thesis. I would also like to acknowledge the following
individuals and groups for their support during my studies at California State University,
Sacramento:

Dr. Kevin Cornwell, CSUS

Dr. Tim Horner, CSUS

Dr. David Evans, CSUS

Dr. Diane Carlson, CSUS

Kent Parrish, URS Corporation

Dr. Miles Roberts, CSUS

Jacques Clouseau

CH2M Hill Inc.

EQUIPCO Corp.

Instrumentation Northwest Inc.
vii
TABLE OF CONTENTS
Dediction ...........................................................................................................................vi
Acknowledgements ......................................................................................................... vii
List of Tables .....................................................................................................................xi
List of Figures ................................................................................................................. xii
Chapter
1. INTRODUCTION .......................................................................................................... 1
1.1
Purpose ......................................................................................................... 4
1.2
Meadow Location ......................................................................................... 5
1.3
Reasons for Meadow Selection .................................................................... 6
Size and Boundaries ................................................................................................. ..6
Accessibility ............................................................................................................... 7
Elevation..................................................................................................................... 7
Healthy Status ............................................................................................................ 7
1.4
Figures .......................................................................................................... 9
2. METHODS................................................................................................................... 16
2.1 Introduction ............................................................................................................ 16
2.2 Calculating the Volume of the Meadow ................................................................ 16
Topographic Data ..................................................................................................... 17
Seismic Refraction Surveys ..................................................................................... 17
Limitations of Seismic Refraction Surveys .............................................................. 19
2.3 Soil Borings ............................................................................................................ 19
2.4 Piezometer Installation ........................................................................................... 19
2.5 Determining Effective Porosity.............................................................................. 20
Methods Used ........................................................................................................... 20
Limitations of Determining the Effective Porosity .................................................. 22
2.6 Ground Water Level and Temperature Measurements .......................................... 22
viii
2.7 Weir Construction and Surface Water Level Measurements ................................. 23
2.8 Outflow Overflow Area ......................................................................................... 25
2.9 Precipitation Data ................................................................................................... 26
2.10 Slope Run-off ....................................................................................................... 27
2.11 Evapotranspiration ............................................................................................... 28
2.12 Developing a Water Budget ................................................................................. 28
2.13 Estimating Residence Time of Water in the Meadow.......................................... 29
2.14 Figures .................................................................................................................. 30
3. GEOLOGY AND HYDROGEOLOGY ...................................................................... 44
3.1 Regional Geologic Setting ..................................................................................... 44
3.2 Site Specific Geology ............................................................................................. 45
3.4 Hydrogeology ......................................................................................................... 46
3.5 Figures .................................................................................................................... 48
4. RESULTS..................................................................................................................... 53
4.1 Determining the Specific Yield of Water in the Meadow ...................................... 53
Lab Results ............................................................................................................... 53
Determining the Volume of Meadow Sediments ..................................................... 54
Calculating the Specific Yield of the Meadow ........................................................ 56
Limitations of Determining the Effective Porosity .................................................. 59
4.2 Groundwater Fluctuations ...................................................................................... 59
Limitations ............................................................................................................... 60
4.3 Surface Water Level Data ...................................................................................... 63
4.3.1 Outflow Culvert and Overflow Channel ............................................................. 66
Piezometer Breakage ................................................................................................ 68
Compensating for Unrealistic Pressure Increase ...................................................... 68
4.3.2 Overflow Channel ............................................................................................... 69
Limitations ............................................................................................................... 72
ix
4.3.3 Eastern Inflow ..................................................................................................... 72
4.3.4 Western Inflow .................................................................................................... 74
4.3.5 Northern Inflow ................................................................................................... 75
4.4 Precipitation ........................................................................................................... 77
Meadow Precipitation .............................................................................................. 77
Slope Run-Off .......................................................................................................... 78
4.5 Evapotranspiration ................................................................................................. 79
4.6 Calculating Water Budget ...................................................................................... 80
4.7 Estimating Residence Time Based on Daily Discharge Peaks .............................. 81
4.8 Short-Term Fluctuations in Water Level ............................................................... 85
Limitations ............................................................................................................... 88
4.8 Figures .................................................................................................................... 90
5. CONCLUSIONS ........................................................................................................ 110
Appendix A. Seismic Survey Data ................................................................................. 112
Appendix B. Soil Boring Logs ....................................................................................... 131
Appendix C. Piezometer Construction Details .............................................................. 153
Appendix D. Lab Reports and Standard Operating Procedures ..................................... 155
Appendix E. Groundwater Level and Temperature Graphs ........................................... 164
Appendix F. Overflow Channel Discharge Calculations ............................................... 176
References ...................................................................................................................... 183
x
LIST OF TABLES
Page
Table 2-1: Calculating the volume of sediments in the meadow ..................................... 16
Table 2-2: Calculating the depth to bedrock in the meadow............................................ 18
Table 2-3: Calculating specific yield ............................................................................... 21
Table 2-4: Calculating the discharge using height measurements ................................... 24
Table 2-5: Calculating the overflow discharge ................................................................ 25
Table 2-6: Calculating change in storage ........................................................................ 28
Table 4-1: Porosity results .............................................................................................. 53
Table 4-2: Grain size results............................................................................................. 54
Table 4-3: Compiled seismic survey velocities and estimated bedrock depths ............... 54
Table 4-4: Calculating the volume of sediments in the meadow ..................................... 56
Table 4-5: Calculating the specific yield of the meadow ................................................. 58
Table 4-6: Average groundwater level data ..................................................................... 60
Table 4-7: Average daily discharge (af/day) .................................................................... 64
Table 4-8: Calculating the surface water inflow and outflow .......................................... 66
Table 4-9: Calculating overflow channel discharge during the high flow ....................... 70
Table 4-10: Estimating overflow discharge from water level .......................................... 71
Table 4-11: Calculating snow and rain direct input ......................................................... 78
Table 4-12: Calculating slope run-off .............................................................................. 79
Table 4-13: Calculating change in storage ....................................................................... 80
Table C-1: Piezometer Construction Details .................................................................. 154
Table F-1: Overflow channel calculations- water level 2.4 ft ........................................ 177
Table F-2: Overflow channel calculations- water level of 2.2 ft ................................... 178
Table F-3: Overflow channel calculations- water level of 2.0 ft ................................... 179
Table F-4: Overflow channel calculations- water level of 1.82 ft ................................. 180
xi
LIST OF FIGURES
Figure 1-1: Conceptual diagram of a healthy meadow ...................................................... 9
Figure 1-2: Conceptual drawing of a degraded meadow. ................................................ 10
Figure 1-3: Aerial photograph of Big Flat Meadow before remediation. ........................ 11
Figure 1-4: Aerial photo of Big Flat Meadow following remediation ............................. 12
Figure 1-5: Location and meadow features ...................................................................... 13
Figure 1-6: The Van Vleck Meadow from the southwest looking northeast ................... 14
Figure 1-7: The Van Vleck Meadow from the southwest looking northeast ................... 15
Figure 2-1: Meadow study features .................................................................................. 30
Figure 2-2: Seismic survey diagram................................................................................. 31
Figure 2-3: Photo of enhanced engineering seismograph ................................................ 32
Figure 2-4: Photo of geophones and attachment cable .................................................... 33
Figure 2-5: Conceptual diagram of weir, piezometer, and transducer ............................. 34
Figure 2-6: Photo of eastern inflow weir and piezometer ................................................ 35
Figure 2-7: Photo of northern inflow weir ....................................................................... 36
Figure 2-8: Photo of the western inflow........................................................................... 37
Figure 2-9: Photo of outflow culvert ................................................................................ 38
Figure 2-10: Conceptual drawing of the outflow area ..................................................... 39
Figure 2-11: Air temperature and precipitation................................................................ 40
Figure 2-12: Accumulated rain from 2003 through 2010 ................................................ 41
Figure 2-13: Snow data from 2000 through 2010 ............................................................ 42
Figure 2-14: Water budget input and output factors ........................................................ 43
Figure 3-1: Regional geology.......................................................................................... 48
Figure 3-2: Map of local geology. .................................................................................... 49
Figure 3-3: Bedrock depth map and cross section locations ............................................ 50
xii
Figure 3-4: Cross section view of meadow along transect line A-A’ .............................. 51
Figure 3-5: Cross section view of meadow along transect line B’-B............................... 51
Figure 3-6: Cross section view of meadow along transect line C’-C............................... 52
Figure 3-7: Cross section view of meadow along transect line D’-D .............................. 52
Figure 4-1: Calculating meadow volume ......................................................................... 90
Figure 4-2: Average groundwater levels .......................................................................... 91
Figure 4-3: Outflow water levels ..................................................................................... 92
Figure 4-4: Outflow weir and overflow channel discharge.............................................. 93
Figure 4-5: Outflow discharge and temperature .............................................................. 94
Figure 4-6: Outflow discharge and precipitation ............................................................. 95
Figure 4-7: Eastern inflow water levels ........................................................................... 96
Figure 4-8: Eastern inflow discharge and temperature .................................................... 97
Figure 4-9: Eastern inflow discharge and precipitation ................................................... 98
Figure 4-10: Western inflow water levels ........................................................................ 99
Figure 4-11: Western inflow discharge and temperature ............................................... 100
Figure 4-12: Western inflow discharge and precipitation .............................................. 101
Figure 4-13: Northern inflow water levels ..................................................................... 102
Figure 4-14: Northern Inflow discharge and temperature .............................................. 103
Figure 4-15: Northern Inflow discharge and precipitation ............................................ 104
Figure 4-16: Discharge peak comparison – eastern inflow and outflow discharge ....... 105
Figure 4-17: Discharge peak comparison – surface water ............................................. 106
Figure 4-18: Peak discharge comparison – November, 2009 ........................................ 107
Figure 4-19: Total input and total output ....................................................................... 108
Figure 4-20: Short term water level readings ................................................................. 109
Figure A-1: Seismic Survey Data for Survey S-01 ........................................................ 113
Figure A-2: Seismic Survey Data for Survey S-02 ........................................................ 115
Figure A-3: Seismic Survey Data for Survey S-03 ........................................................ 117
xiii
Figure A-4: Seismic Survey Data for Survey S-04 ........................................................ 119
Figure A-4: Seismic Survey Data for Survey S-04 ........................................................ 119
Figure A-5: Seismic Survey Data for Survey S-05 ........................................................ 121
Figure A-6: Seismic Survey Data for Survey S-06 ........................................................ 123
Figure A-7: Seismic Survey Data for Survey S-07 ........................................................ 125
Figure A-8: Seismic Survey Data for Survey S-08 ........................................................ 127
Figure A-9: Seismic Survey Data for Survey S-09 ........................................................ 129
Figure B-1: Soil Boring SB-01 ...................................................................................... 132
Figure B-2: Soil Boring SB-02 ...................................................................................... 133
Figure B-3: Soil Boring SB-03 ...................................................................................... 134
Figure B-4: Soil Boring SB-04 ...................................................................................... 135
Figure B-5: Soil Boring SB-05 ...................................................................................... 136
Figure B-6: Soil Boring SB-06 ...................................................................................... 137
Figure B-7: Soil Boring SB-07 ...................................................................................... 138
Figure B-8: Soil Boring SB-08 ...................................................................................... 139
Figure B-9: Soil Boring SB-09 ...................................................................................... 140
Figure B-10: Soil Boring SB-10 .................................................................................... 141
Figure B-11: Soil Boring SB-11 .................................................................................... 142
Figure B-12: Soil Boring SB-12 .................................................................................... 143
Figure B-13: Soil Boring SB-13 .................................................................................... 144
Figure B-14: Soil Boring SB-14 .................................................................................... 145
Figure B-15: Soil Boring SB-15 .................................................................................... 146
Figure B-16: Soil Boring SB-16 .................................................................................... 147
Figure B-17: Soil Boring SB-17 .................................................................................... 148
Figure B-18: Soil Boring SB-18 .................................................................................... 149
Figure B-19: Soil Boring SB-19 .................................................................................... 150
Figure B-20: Soil Boring SB-20 .................................................................................... 151
xiv
Figure B-21: Soil Boring SB-21 .................................................................................... 152
Figure D-1: Grain size summary .................................................................................... 156
Figure D-2: Effective porosity results ............................................................................ 159
Figure D-3: Grain size analysis SOP.............................................................................. 160
Figure D-4: Effective porosity SOP ............................................................................... 162
Figure E-1: Water levels and average temperature at piezometer PZ-01 ...................... 165
Figure E-2: Water levels and average temperature at piezometer PZ-03 ...................... 166
Figure E-3: Water levels and average temperature at piezometer PZ-04 ...................... 167
Figure E-4: Water levels and average temperature at piezometer PZ-05 ...................... 168
Figure E-5: Water levels and average temperature at piezometer PZ-06 ...................... 169
Figure E-6: Water levels and average temperature at piezometer PZ-07 ...................... 170
Figure E-7: Water levels and average temperature at piezometer PZ-08 ...................... 171
Figure E-8: Water levels and average temperature at piezometer PZ-10 ...................... 172
Figure E-9: Water levels and average temperature at piezometer PZ-11 ...................... 173
Figure E-10: Water levels and average temperature at piezometer PZ-12 .................... 174
Figure E-11: Water levels and average temperature at piezometer PZ-13 .................... 175
Figure F-1: Outflow area plan view ............................................................................... 181
Figure F-2: Outflow area profile view ........................................................................... 182
xv
1
Chapter 1
INTRODUCTION
Alpine meadows play an important role in California’s water resources for
several reasons, including their ability to inhibit water from moving quickly downstream
(Stohlgren et al., 1989), and their contribution to recharging groundwater (Smerdon et.
al, 2009). The most current definition of a healthy meadow provided by American
Rivers Technical Advisory Committee (American River, 2010) suggests:
"A mountain meadow is an ecosystem type composed of one or more plant
communities dominated by herbaceous species and supports plants that use surface
water and/or shallow ground water (generally at depths of less than one meter). Woody
vegetation (e.g., trees and shrubs such as Alnus and Salix) may occur, and be locally
dense, but are not dominant."
Alpine meadows usually form in areas underlined by low-permeability bedrock
with a gently sloping surface. Water is captured in the meadow from springs, creeks, or
precipitation runoff and migrates slowly through the meadow (Wood, 1975). Figure 1-1
is a conceptual diagram depicting a typical healthy meadow (American Rivers, 2010).
Wet meadow and riparian vegetation is supported by a high water table. Stream
channels are sinuous and the meadow is inundated during floods, which allows for
2
sediment deposition and flood attenuation. A healthy meadow will receive snowmelt via
surface and subsurface flow.
Beneficial meadow functions include reducing sediment load and improving
quality of water flowing downstream, providing habitat for unique flora and fauna,
storing groundwater, and aiding in flood attenuation (Ponce and Lindquist, 1990). Water
from precipitation, streams, or springs percolates through meadow sediments and is
attenuated (Ponce and Linquist, 1990). Conversely, water stored in the meadow acts as a
supply to downstream reservoirs, slowly releasing water during the dry seasons
(Stillwater Sciences, 2008, Ponce and Lindquist, 1990).
Many meadows in the Sierra Nevada Mountains have shown signs of being
disturbed or degraded years of overgrazing, fire suppression, recreation, and other
human related activities (Stillwater Sciences, 2008). Signs of degradation include the
presence of incised stream channels where soil is easily exposed and eroded, which can
lead to changes in vegetation (American River, 2010). Figure 1-2 is a conceptual
diagram depicting an unhealthy meadow (American River, 2010). Unhealthy meadows
experience soil compaction, a reduction in percolation, and reduction in diversity and
productivity. Flooding events do not inundate the meadow, but are confined to the
stream channel area. Stream incision occurs when water moves through stream channels
during flood events and erodes alluvium along the stream banks. As this alluvium is
removed, more non-vegetated area is exposed and the incision process continues (Ponce
3
and Lindquist, 1990). With the continuation of alluvium removal and channel incision
and increased sediment load, the water table decreases. Water quality decreases with an
increase in suspended sediment that was eroded from the exposed stream banks
(American Rivers, 2010). Flow from snowmelt reaches the meadow only via surface
flow in unhealthy meadows. As the water table decreases, a larger gap is created
between the water table and the meadow’s surface. Eventually, the vegetation root
systems and the types of vegetation change due to the lowering of the water table
(Stillwater Sciences, 2008). If incised channels are present in a meadow, less runoff is
absorbed into the meadow sediments. This increased runoff will flow downstream and
increase the risk of flooding as well as decrease water quality for the reasons mentioned
above. Incised channels lead to a diminished water supply because the water table is
lowered and water flows out of the meadow as opposed to percolating slowly through
the meadow (Stillwater Sciences, 2008).
In general, water in California is becoming a more scarce resource as supply
decreases and demand increases (California DWR, 2003). Water supply issues are
becoming increasingly important (Hammersmark et. al, 2008) and meadow and stream
restoration projects, in particular those involving the “pond and plug” method, aim to
improve aesthetics, rehabilitate the habitat, improve water quality by limiting stream
bank erosion, elevate the water table, and increase groundwater storage (Rosgen, 1997).
The “pond and plug” method involves moving meadow sediment from one part of the
4
meadow (creating ponds), and using it to plug the incised areas of the channel
(Hammersmark et. al, 2008). Figure 1-3 is an aerial photograph showing the degraded
Big Flat Meadow prior to being restored using the “pond and plug” method (Lindquist
and Wilcox, 2000). The incised channel is shown in the bottom right part of the photo.
Figure 1-4 presents the same meadow after restoration (Lindquist and Wilcox, 2000).
The pond areas in the central part of the photo are located where the incised channel was
prior to restoration.
1.1 Purpose
The quantitative hydrologic effects of meadows are not fully documented
(Lindquist and Wilcox, 2000). Understanding the hydrologic functions of a healthy
meadow will assist in determining the role that meadows play in increasing flood
attenuation and groundwater storage. The purpose of this study is to assess how
meadows aid in flood attenuation and groundwater storage of the Van Vleck meadow in
the Sierra Nevada Mountain Range. A water budget for the meadow was developed to
understand the quantity and timing of water entering and leaving the meadow
throughout the 2009-2010 water year. The water budget was developed by tracking the
quantity of water entering and exiting the meadow. The water storage capacity, the
maximum theoretically accessible capacity of the meadow, was estimated based on the
data collected for the water budget in addition to other field studies, which will be
described below in Section 2. Flood attenuation parameters were assessed by comparing
5
the trend of how water quantities increased during the winter and spring, and how
quantities decreased in the summer based on the amount of water entering and exiting
from surface water locations. Slope run-off, evapotranspiration and precipitation were
also considered factors of the water budget.
1.2 Meadow Location
The Van Vleck Meadow is located in the El Dorado National Forest,
approximately 70 miles east of Sacramento, California (Figure 1-5). The center of the
meadow is located at 38°56’14.08”N and 120°19’05.80”W at approximately 6,550 feet
AMSL (above mean sea level). The elevation of the piezometers within the meadow
range from approximately 6,159 to 6,193 ft AMSL based on collected surveying data.
The center point of the meadow is slightly elevated due to outcropping bedrock.
The meadow is approximately 61.4 acres in area and located within the
American River drainage basin. Five culverts funnel surface water to the meadow and
one culvert drains water out of the meadow via Tells Creek (Figure 1-5). Tells Creek
enters the meadow through the eastern culvert and flows along the southeastern edge of
the meadow and exits the meadow through the outflow culvert at the south end of the
meadow. A berm bisects the north area of the meadow, which has an opening that
allows water from the three northern most culverts to flow into the center of the
meadow.
6
Located approximately one half mile from the meadow, the Van Vleck Weather
Station typically records 55 to 65 inches of rain and 28 to 58 inches of snow (measured
in water content) per year (California DWR, 2011).
The meadow is surrounded by multiple peaks that are roughly 7,000 feet AMSL.
Approximately three miles southeast, the mountains Two Peaks have an elevation of
7,600 feet AMSL and are the highest local surface relief.
1.3 Reasons for Meadow Selection
Size and Boundaries
The 61.4-acre Van Vleck Meadow is capable of storing larger amounts of water
than smaller meadows in the Sierra Nevada Mountains. Other watersheds within
Northern California contain meadows that are smaller than the Van Vleck Meadow,
such as meadows in the Cosumnes, American, Yuba, and Bear watersheds; however, the
meadow’s size may be similar to the size of other meadows that would be considered
acceptable to restore (Stillwater Sciences, 2008).
The meadow has discernable
boundaries. The southern portion of the meadow is bordered by a United States Forest
Service (USFS) road while the northern portion is bordered by a dirt road and walking
path. Tells Creek is the only stream present and borders the southeastern edge of the
meadow.
7
Accessibility
The meadow location was ideal from a logistical standpoint because it is close
enough to visit for a one- day trip to download data and inspect equipment, yet is remote
enough that vandalism of equipment is not of great concern. The meadow is accessible
from Cheese Camp Road/ USFS road, 6.7 miles from off Highway 193 when snow has
not accumulated on the USFS road. The USFS road is not plowed during the winter
months. However, a cross-country ski trail is marked from Loon Lake to the Van Vleck
meadow.
Elevation
The elevation of the meadow, ranging from 6,159 to 6,550 feet AMSL at the
edges, is also representative of a large portion of alpine meadows in the El Dorado
National Forest (Stillwater Sciences, 2008). The meadow exists above the regular snow
line and the Van Vleck Weather Station is located approximately one mile from the site,
which will yield representative measurements of actual meadow precipitation.
Healthy Status
The Van Vleck Meadow appears to fit the characterization of a healthy meadow
as described above. The observed vegetation appears to be consistent with general
meadow vegetation including forbs, graminoids, grasses and deciduous shrubs. Water
level is relatively close to the ground surface if not at the surface throughout the entire
year. The meadow does not show signs of degradation including concentrated flow paths
8
or incised channels. Figures 1-6 and 1-7 present photographs of the meadow on April
24, 2010 and July 11, 2010 from the same vantage point.
The meadow underwent a controlled burn by the USFS on October 10, 2009.
Prior to the burn, trees along the roads were cut and the timber was left to be burned.
The purpose of the burn was to reduce the timber litter and standing live confers, reduce
the height of the grass components, and consume confer seedlings. Other objectives
were to increase the native shrub and forb species and to stimulate the native seed banks.
The majority of meadow vegetation returned the following year, but many of the trees
that were burned along the edge of the meadow were reduced as a result of the burning.
The activities did not appear to disturb this study.
9
1.4 Figures
Figure 1-1: Conceptual diagram of a healthy meadow (American Rivers, 2010).
10
Figure 1-2: Conceptual drawing of a degraded meadow (American Rivers, 2010).
11
Figure 1-3: Aerial photograph of Big Flat Meadow before remediation (Lindquist and
Wilcox, 2000).
12
Figure 1-4: Aerial photo of Big Flat Meadow following remediation
The “pond and plug” method was used to restore Big Flat Meadow (Lindquist and
Wilcox, 2000).
13
Figure 1-5: Location and meadow features
14
Figure 1-6: The Van Vleck Meadow from the southwest looking northeast
The photo was taken on April 24, 2010.
15
Figure 1-7: The Van Vleck Meadow from the southwest looking northeast
The photo was taken on July 11, 2010 from the same vantage point as the photo
presented in Figure 1-6.
16
Chapter 2
METHODS
2.1 Introduction
The methods described below were used to characterize the meadow, develop a
water budget for the one-year study period, and ultimately quantify the meadow’s flood
attenuation potential. Figure 2-1 shows the locations of collected data performed in this
study.
2.2 Calculating the Volume of the Meadow
The volume of the meadow was calculated to estimate its potential water storage
capacity. In order to calculate the volume, the topographic boundaries were delineated
and the depth to bedrock was calculated by performing seismic surveys across the
meadow. After the horizontal and vertical boundaries were identified using these
techniques, the volume was calculated using the equation below.
Table 2-1: Calculating the volume of sediments in the meadow
V= A1D1 + A2 D2 + A3 D3
Where
V = Volume of the sediments in the meadow
A1 = Area with average bedrock depth D1
D1= Average bedrock depth of 2.5 ft bgs
A2 = Area with average bedrock of D2
D2 = Average bedrock depth of 7.5 ft bgs
A3 = Area with average bedrock of D3
D3 = Average bedrock depth of 12.5 ft bgs
17
Topographic Data
The perimeter of the meadow was traced in Photoshop CS5 from a file originally
created in Global Information Systems (GIS) to estimate the acreage. Based on field
observations, the perimeter of the meadow was generally consistent with the tree line
with exception of the southern border of the meadow, which does not follow the tree
line as distinctly as in other areas (Figure 2-1). The southwestern part of the meadow,
just north of the western inflow weir, has a relatively steeply sloping edge and contains
little vegetation. The soil, lacking organic matter and root mass, was not consistent with
the soil and vegetation in the meadow and was excluded from meadow area calculations.
Seismic Refraction Surveys
Seismic waves travel at different velocities through different materials. Velocity
is higher through dense material compared to less dense material. Seismic primary
waves generally travel at a velocity of 5,000 to 6,000 meters per second through granitic
bedrock rock, 200 to 2,200 meters per second through sand, 400 to 1,500 meters per
second through sand and gravel, and 400 to 2,100 meters per second through glacial till
(Burger, 1992). The vertical boundary of the meadow (depth to bedrock) was identified
by performing seismic refraction surveys. Figure 2-2 shows a schematic of seismic
waves traveling through a horizontal layer of alluvium and bedrock.
Nine seismic surveys were performed using an EG&G Geometrics 12-channel
seismograph because it was portable and had low impact on the meadow. The survey
18
equipment included 12 geophones, a seismograph, battery for power, metal strike plate,
and sledgehammer. The strike plate was placed approximately 7.5 feet (ft) from the first
geophone that was placed 7.5 ft from the second geophone. The remaining geophones
were placed linearly in 15-foot intervals, totaling 165 ft of survey length. Figures 2-3
and 2-4 are photographs of the equipment in use and the geophones. Figure 2-1 presents
the locations where the seismic surveys were preformed. The strike plate was struck
several times at each location to stack data and raise the signal level above background
noise level. Measurements were repeated at opposite ends of the line and arrival times
for both directions were compared and repeated if not within 10 percent. Two seismic
surveys were not used to estimate bedrock because the first arrival times were not
distinct. Bedrock depth was calculated based on the seismic wave patterns and elapsed
time using the formula below (Telford et al., 1990). The time vs. distance graphs for
each seismic study and the calculated bedrock depths are presented in Appendix A. The
results of the seismic surveys, including the calculated velocities and the depth to
bedrock at each location, are discussed in Section 4.
Table 2-2: Calculating the depth to bedrock in the meadow
D = (Xc/2) √ ((V2-V1)/ (V2+V1))
Where
D = Depth to bedrock
Xc = Critical distance where V1 and V2 intersect
V1 = Velocity of sound waves in layer 1
V2 = Velocity of sound waves in layer 2
19
Limitations of Seismic Refraction Surveys
The depth estimate is a factor that may cause variation in estimating the volume
of water potentially stored in the meadow. Seismic surveys are more easily interpreted
in areas with a flat bedrock surface. Based on the survey results, the bedrock in the
meadow may be sloping or uneven. Drilling to bedrock to confirm its depth would allow
for a more accurate estimate of the volume of sediments in the meadow, however, it was
not feasible for this study due to the cost and the sensitive nature of the meadow.
2.3 Soil Borings
Twenty-one soil borings were hand augured throughout the meadow to serve
different purposes (Figure 2-1). The soil boring logs are presented in Appendix B. Ten
soil borings were used to characterize the soil using the Unified Soil Classification
System (ASTM D2488-93). Fifteen soil borings were used to install piezometers and
two soil borings were used to collect soil samples to determine effective porosity.
2.4 Piezometer Installation
Fifteen two-inch piezometers were installed in boreholes throughout the
meadow, 11 of which housed pressure transducers. Figure 2-1 presents the locations of
the piezometers and those that contained transducers. The transducers recorded water
level and temperature every 20 minutes for the entire duration of the study period. The
water level measurements are discussed in more detail in Section 2.6. The piezometers
were spaced throughout the meadow to measure water levels representative of the entire
20
meadow. The piezometers were constructed using schedule 40 polyvinyl chloride (PVC)
riser with a Solinst screen attachment or by cutting holes in the PVC and wrapping and
clamping it with landscape mesh. The boreholes were drilled using a hand auger to
refusal, which was between two and six ft below ground surface. The annulus was filled
with clean sand to one half foot within from ground surface. Native soil was used to fill
the annulus to ground surface above the sand. Each piezometer was capped with a PVC
end cap with a small hole drilled in the top. A wire was attached to the cap that held the
transducer. All Piezometers were surveyed to determine exact location and elevation.
Construction details are presented in Appendix C.
2.5 Determining Effective Porosity
Methods Used
Based on the soil logs and field observations, two zones of soil were present in
the meadow. A representative sample from each zone was collected from soil boring
SB-20 from 1.6 ft below ground surface (bgs) to 2.2 ft bgs and from 2.2 ft bgs to 2.8 ft
bgs. The samples were shipped under chain of custody to PTS Labs where they were
analyzed for effective porosity using American Society for Testing and Materials
(ASTM) method D425M-88 (ASTM D425M-88, 2008) and grain size distribution using
ASTM D422/4464M (ASTM D422/4464M, 2007). The full lab report from PTS and
the standard operating procedures (SOPs) of the methods are presented in Appendix D.
21
American Society for Testing and Materials D425M is a method used to
determine the effective porosity of a soil sample. This method involves using a
centrifuge to spin the soil sample at 1000 times gravity, which is enough to reduce the
capillary fringe forces and remove water from the sample to determine how much water
it can yield.
American Society for Testing and Materials 422/4464M is a method used to
determine the grain size distribution in a soil sample. This method involves sieving the
soil sample using several different sized sieves and calculating the percent of mass left
on each sieve at the end of the test. The soil samples were not sorted past 75
micrometers (No. 200 sieve) because it was unnecessary to determine the effective
porosity of the bulk of the sediments.
The effective porosity of the material was used to calculate the specific yield of
the materials in the meadow using the following equation:
Table 2-3: Calculating specific yield
Sy = (Vtop* Øtop ) + (Vmiddle * Ømiddle) + (Vbottom * Øbottom)
Where,
Sy
= specific yield of the meadow
Vtop
= volume from 0 to 5 ft
= (A1+A2+A3) * H1
Vmiddle
= volume from 5 to 10 ft
= (A2+A3) * H2
Vbottom
= volume from 10 to 15 ft
= A3 * H3
Øtop
= effective porosity of top 2.5 ft
= 35.8%
Ømiddle
= effective porosity from 2.5 to 7.5 ft
= 26.7%
22
Table 2-3 (Continued)
Øbottom
= effective porosity from 7.5 to 12.5 ft
= 21.0%
A1
= area with average depth of 2.5 ft to bedrock
= 17.5 acres
A2
= area with average depth of 7.5 ft to bedrock
= 26.6 acres
A3
= area with average depth of 12.5 ft to bedrock
= 17.3 acres
H1
= average change in depth from 0 to 5 ft
= (5ft – 0ft)/2 = 2.5 ft
H2
= average change in depth from 5 to 10 ft
= (10ft – 5ft)/2 = 2.5 ft
H3
= average change in depth from 10 to 15 ft
= (15ft – 10ft)/2 = 2.5 ft
Note:
Area measurements are discussed in Section 4
Limitations of Determining the Effective Porosity
The estimate of the specific yield is approximate and depends on the accuracy of
input variables. Little is known about the sediments below five or six ft in the meadow.
Hand auguring only gave a limited view of what kinds of sediments were present.
Depending on the effective porosity of the deeper sediments, the volume of water stored
in the meadow could vary. In general, coarse gravel can range from 13% to 25% for
effective porosity with a mean of 21% (McWorter and Sunada, 1977). An effective
porosity value of 21% was used for the deeper sediments, but if it varied greatly the
potential volume of water in the meadow could vary as well. Justification for using an
effective porosity value of 21% for the deeper sediments is discussed further in Section
4.
2.6 Ground Water Level and Temperature Measurements
The ground water level measurements were used to estimate the volume of water
stored in the meadow. The remote location of the meadow and deep snow conditions
23
limited the ability to manually record water levels throughout the study period. In order
to accurately capture groundwater fluctuations during the study period, 11 pressure
transducers were installed in the piezometers. The Solinst Level Logger 3001 transducer
was used due to its high sensitivity. Each transducer was installed in a piezometer one
foot (PZ-01, PZ-03 through PZ-06) or one inch from the bottom of the piezometer (PZ07, PZ-08, and PZ-10 through PZ-13). Figure 2-1 presents the locations of piezometers
containing transducers. The transducer measured the pressure induced by the water
column above the transducer and the temperature. The pressure was converted to height
of the water column by multiplying the pressure, measured in pounds per square inch
(psi), by 2.31 ft. Pressure and temperature readings were automatically recorded by the
data logger every 20 minutes. The data were downloaded onto a laptop computer in July
and October 2010. Appendix E contains the graphed water level and temperature data.
2.7 Weir Construction and Surface Water Level Measurements
Four 90-degrees “V”-notch weirs were constructed at the inflow and outflow
locations in the meadow, which are referred to as the eastern inflow weir, western
inflow weir, northern inflow weir, and the outflow weir. The eastern, western, and
outflow weirs were attached to preexisting culverts. The northern weir was constructed
in the opening in the berm and funneled flow from three up-gradient culverts into the
meadow (Figure 1-5). Figure 2-5 presents a conceptual drawing of the water flowing
through the weir and the placement of the piezometer and transducer. The weirs were
constructed from ossified stranded board and plywood to fit over the face of the culvert
24
(or in the berm) and allow water to flow through the notch. A transducer was installed in
a piezometer two to four ft upstream of each weir to measure the height of the water
flowing through the notch. Figures 2-6 through 2-9 present photographs of each weir.
The height measurement allowed later calculation of how much water passed through
the weir. The transducer data were calibrated by manually recording water levels during
different flow heights.
The following equation was used in conjunction with the manual measurements
to estimate the flow through the weirs (United States Department of the Interior, Bureau
of Reclamation, 2001):
Table 2-4: Calculating the discharge using height measurements
Q = 2.49h12.48
Where
Q = discharge over the weir (ft3/s)
h1 = head on the weir (ft)
This equation is most accurate when estimating the discharge rate through a 90degree “V”-notch weir at rates from 0.05 ft3/s (22 gallons per minute [gpm]) to 255 ft3/s
(1,908 gpm). The flow did not reach the maximum flow rate for the use of this equation.
However, the discharge rate dropped below 22 gpm during dry months. Accurate flow
measurements were collected manually during site visits by timing how long it took
water to fill a five-gallon bucket. The water levels recorded by the transducer during the
low flow months were calibrated using the manually recorded or visually observed
25
water levels. If the recorded or observed water level was significantly lower or higher
than the manually recorded reading, the difference between the recorded level and the
actual measured level was either added or subtracted from the recorded water level. The
weirs required little to no maintenance during the study period.
2.8 Outflow Overflow Area
During a site visit on June 26, 2010, water was observed flowing around the
outflow culvert, over the roadway. At this time, the water flowing over the road was less
than two inches deep. However, higher water marks were observed. Figure 2-10 presents
a conceptual diagram of the outflow culvert and the overflow area. The roadway where
water flooded and the channel immediately upstream of the outflow culvert were
surveyed. The survey data were plotted in Excel and the volume of water potentially
moving through the overflow channel at the highest possible flow was calculated. Table
2-5 presents a summary of the equation used for solving for overflow discharge using
the Manning Equation.
Table 2-5: Calculating the overflow discharge
Q = (1.0/n) A (R2/3) (S1/2)
Where
Q = Discharge, m3/s
n = Manning roughness coefficient, 0.028 for coarse gravel (Cowan, 1956)
A = cross-sectional area of channel, m2
R = hydraulic radius = A/P in m where
S = bottom slope of channel, m/m
P = wetted perimeter of cross-sectional flow area, m
26
Based on the survey data, water began to overflow into the channel when water
level at the outflow weir reached 1.65 ft. Four ranges of overflow discharge were
calculated using outflow weir water levels of 2.4 ft, 2.2 ft, 2 ft, and 1.82 ft. The
calculations for each discharge range are provided in Appendix F.
2.9 Precipitation Data
In order to estimate the total input of precipitation directly contributing to the
water budget, the total precipitation (rain and snow) during the study period was
multiplied by the meadow area. Precipitation data were recorded at the Van Vleck
Meteorological Station (Van Vleck Station) operated by Sacramento Municipal Utilities
District (SMUD) located 0.5 miles northeast from the meadow. Snow data recorded at
the station from 2009 through 2010 were retrieved from the California Department of
Water Resources California Data Exchange Center (CDEC) website. The Precipitation
as rain data were unavailable through the CDEC website and were received directly
from SMUD. Figure 2-11 presents the air temperature and precipitation that occurred at
the Van Vleck Station during the study period. Longer term precipitation records for
rain and snow were graphed and downloaded from the CDEC website and are provided
in Figures 2-12 and 2-13. Figure 2-12 presents the precipitation data as rain that was
reported from 2003 through 2010. Figure 2-13 presents the snow data reported as water
content (the amount of water contained in the snow) recorded from 2000 through 2010.
27
2.10 Slope Run-off
Based on field observations, much of the sloping area around the meadow
appears to directly run-off toward an inflow weir (which already accounts for the inflow
as surface flow). However, some sloping areas likely contribute water directly to the
meadow that did not flow through a weir. Slope run-off was calculated by multiplying
the area of the slope by 68% of the precipitation received (based on the precipitation
estimates discussed above). Sixty-eight percent of the total precipitation was used
instead of 100% because not all of the precipitation that falls on the meadow contributed
to slope run-off. Some water is retained in the soil. The estimate of 68% was based on a
comparison from the area upslope of the northern weir, where the amount of rain and the
amount of discharge through the weir was known. During a rain event from December 6
through 10, 2009, 6.1 inches (0.51 ft) of rain were recorded at the Van Vleck Station.
The area upslope area of the northern weir was multiplied by the total feet of rainfall
(250 acres x 0.51 ft = 127.5 af of water) to calculate the total volume of rain that fell upgradient of the northern weir that potentially passed through the northern weir. The
increase in height at the weir was noted and the total increase in volume that occurred
after the precipitation even was calculated at 87 af for that storm event. Sixty-eight
percent (87 af/127.5 af) of the total rainfall passed through the weir.
A topographic map was used to outline the areas that would likely contribute
slope run-off towards the meadow and is shown in Figure 2-14. The area was
determined using the common area wand tool in Photoshop CS5. The areas in Figure 2-
28
14 were multiplied by 68% of the total rainfall experienced to estimate how much water
was contributed to the meadow via slope run-off.
2.11 Evapotranspiration
Evapotranspitation was estimated using the Monthly Average Reference
Evapotranspiration by ETo Zone (University of California, Davis and California
Department of Water Resources, 1999). The area of the meadow within the weirs, 59.1
acres (61.4 acres – 2.3 acres north of northern weir), was multiplied by the annual
evapotranspiration rate of 4.5 ft.
2.12 Developing a Water Budget
To develop a water budget, the total inflow values and total outflow values were
estimated. Figure 2-14 presents a schematic of the input and output factors that were
accounted for in the water budget. The change in storage was calculated using the
equation in table 2-6.
Table 2-6: Calculating change in storage
Change in Storage = Input – Output
Input Factors
Output Factors
Surface water entering through three inflow weirs
Surface water exiting through the outflow weir
Precipitation directly on the meadow
Surface water flooding the overflow channel and
over road during periods of high flow
Slope runoff not captured through an inflow weir
Evapotranspiration
Groundwater intrusion into the meadow was not considered significant and not
factored in the equation because the meadow is surrounded by outcropping bedrock.
29
However, little is known about bedrock fractures beneath the meadow alluvium. The
amount of water that possibly enters or leaves the meadow via bedrock fractures is
discussed in Section 4.
2.13 Estimating Residence Time of Water in the Meadow
In order to calculate the residence time of water in the meadow, the timing of
discharge peaks for the input and the output locations were compared. The sensitivity of
the transducers combine with turbulence in the weirs presented a significant limitation
with drawing comparisons based on one daily reading. However, the few input and
output peaks that appeared distinct were compared. The delay between the inflow
discharge peak and the outflow discharge peak was identified as the residence time of
water in the meadow. Precipitation and slope run-off discharge peaks and troughs were
also compared to the outflow discharge peaks.
Another limitation with identifying the residence time of water in the meadow
using the comparison of quantities of discharge is that the majority of discharge enters
through the eastern weir via Tells Creek to the outflow weir. The water has a
significantly shorter residence time if starting from the eastern inflow weir compared to
the northern or western inflow weir based on distance and flow path. The large quantity
of the peak from the eastern inflow weir may mask the other inflow discharge peaks of
smaller quantities.
30
2.14 Figures
Figure 2-1: Meadow study features
31
hammer
strike
plate
geophones
Bedrock
alluvium
(waves
travel at
higher
velocity)
bedrock
Figure 2-2: Seismic survey diagram
surface wave
32
Figure 2-3: Photo of enhanced engineering seismograph
33
Figure 2-4: Photo of geophones and attachment cable
34
Figure 2-5: Conceptual diagram of weir, piezometer, and transducer
35
Figure 2-6: Photo of eastern inflow weir and piezometer
The photo was taken on October 23, 2010.
36
Figure 2-7: Photo of northern inflow weir
The photograph was taken on November 15, 2009.
37
Figure 2-8: Photo of the western inflow
The photograph was taken before water began flowing on October 9, 2009.
38
Figure 2-9: Photo of outflow culvert
The photograph was taken on November 5, 2010.
39
Figure 2-10: Conceptual drawing of the outflow area
The dashed line shows the elevation of the high water mark where water flows through
the overflow channel over the road. The dash-dotted line shows the elevation where
water begins to flow through the overflow channel.
40
Figure 2-11: Air temperature and precipitation
40
41
Figure 2-12: Accumulated rain from 2003 through 2010
42
Figure 2-13: Snow data from 2000 through 2010
43
Figure 2-14: Water budget input and output factors
43
44
Chapter 3
GEOLOGY AND HYDROGEOLOGY
3.1 Regional Geologic Setting
The regional geology is characterized by Mesozoic igneous granodiorite bedrock
which is part of the Sierra Nevadan batholith (Norris and Webb, 1990 and Strand and
Koenig, 1965) overlain by alluvium consisting of glacial deposits and local weathered
rock. The Sierran Batholith is composed of various plutons that were formed prior to the
Cenozoic period (Cecil et al, 2006). Uplift and western tilting that occurred during the
past five million years are mostly responsible for the erosion rates and subsequent
modern topography (Harden, 2004). Sequences of Paleozoic marine dolomite/limestone
and Pliocene volcanic pyroclastic rocks are present ten miles west of the meadow and
continue toward the Sierra Nevada foothills. Further west in the foothills, a
metavolcanic belt is present, and is mostly comprised of Upper Triassic marine rocks
and Jurassic-Triassic metavolcanic rocks. Some areas within the metamorphic belt
contain Mesozoic basic and ultrabasic intrusive rocks as well as pre-Cretaceous
metamorphic limestone. Two miles north- northeast of the meadow, middle to lower
Jurassic marine rocks are present (Strand and Koenig, 1965). Figure 3-1 presents a map
of the regional geology of the area surrounding the meadow.
No faults are documented in the immediate vicinity of the meadow.
Approximately ten miles to the northwest, a fault is present and strikes in the northwestsoutheast direction. Faults are present in the Lake Tahoe Basin and the region to the east
45
of the meadow (Kent et. al, 2005). Areas of faulting are also present throughout the
metamorphic belt in the Sierra Nevada Foothills to the west of the meadow.
3.2 Site Specific Geology
Glacial deposits from the Pleistocene are present throughout the area. The
alluvium in the meadow is composed mostly of recent weathered material from the
surrounding slopes. A combination of peat and organic zones, silt, sand and gravelly
alluvium was observed in boreholes. Figure 3-2 presents a local geologic map of the
Van Vleck Meadow and surrounding area.
The upper layer of soil encountered in the meadow, typically observed just
below the root mass to two ft below ground surface, consists of silt or sandy silt. The
second layer of soil, typically encountered below two ft below ground surface, was
medium to fine sand with occasional fine gravel.
Bedrock is exposed at the surface of the meadow in some areas and extends up to
16 feet below ground surface (ft bgs) as indicated by the seismic surveys but typically
do not extend past 12.5 ft bgs. The estimated bedrock depth map is presented in Figure
3-3. Generally, the bedrock is most shallow along the edges of the meadow and in the
central area of the meadow where bedrock outcrops. Four cross sections are presented in
Figures 3-4 through 3-7. The results for bedrock depth are discussed in more detail in
Section 4.
46
3.4 Hydrogeology
Regional annual precipitation typically ranges between 45 and 65 inches of rain
and between 28 and 58 inches of snow measured in water content (California DWR,
2011). Snow as water content is the measured amount of water that is produced when
the snow is melted (United States Department of Commerce, National Oceanic
Atmospheic Administration, 2011). Precipitation typically occurs between October and
April in an average year. See Figures 2-11 and 2-12 for rain and snow trends from 2000
and 2003 through 2010. Thunder and lightning storms with relatively low amounts of
precipitation are common during the summer months (California DWR, 2011).
The annual lake evaporation rate in the study area (and much of northern
California) is 40 to 50 inches (3.3 ft to 4.2 ft) (Data from United States Geological
Survey, 1968). Although the meadow is not fully saturated with water available above
the ground surface during all of the year, such as a lake, this estimate gives the highest
possible evaporation rate for a conservative estimate if the water were available.
Evapotranspiration was estimated at 258 af for the study period (4.2 ft x 61.4 acres).
During the study period, groundwater levels ranged from above ground surface
to approximately two ft below ground surface. Groundwater levels fluctuate throughout
a given year and from year to year.
The meadow has five sources of surface water. Three of the five inflow points
are located in the northernmost 2.3 acres of the meadow, north of the berm that bisects
47
this part of the meadow (Figure 1-5). The northern weir was constructed in a 10-foot
opening in the center of the berm. The weir allowed water to flow in from the three
inflow culverts that did not contain weirs. Precipitation that fell directly on the 2.3 acres
and the run-off from the surrounding slopes also passed through this weir.
Tells Creek, which enters the meadow at the eastern inflow culvert (Figure 2-6),
flows southwest through the eastern edge of the meadow. Tells Creek originates as a
spring approximately a mile northeast of the meadow. After passing through the outflow
weir at the south end of the meadow (Figure 2-9), the water continues flowing to the
west and empties into Union Valley Reservoir, which drains to the South Fork of the
American River. Tells Creek was dry during the fall of 2009 when the outflow weir was
installed. Water continued flowing from Tells creek through the summer and fall of
2010. The western culvert enters the meadow on the western side of the meadow
(Figure 2-8). The western inflow weir is the smallest of all the locations and did not
contribute as much water to the meadow compared to the other locations.
48
3.5 Figures
Figure 3-1: Regional geology
Qal – Alluvium, Qg – Glacial deposits, Qpvb – Pleistocene volcanic, basalt, gra –
Mesozoic granite rocks, granite and adamellite, grt - Mesozoic granite rocks, tonalite and
diorite (Strand and Koenig, 1965).
49
Figure 3-2: Map of local geology.
The original map is 1:24,000 Loon Lake Topographic Quadrangle (USGS, 1993), and
was modified by Lesh, 2010. Qal – Alluvium, Qg – Glacial deposits.
50
Figure 3-3: Bedrock depth map and cross section locations
51
Figure 3-4: Cross section view of meadow along transect line A-A’
Figure 3-5: Cross section view of meadow along transect line B’-B
52
Figure 3-6: Cross section view of meadow along transect line C’-C
Figure 3-7: Cross section view of meadow along transect line D’-D
53
Chapter 4
RESULTS
4.1 Determining the Specific Yield of Water in the Meadow
In order to determine the specific yield of the groundwater aquifer underlying the
meadow, the volume of the sediments within the meadow and the effective porosity of
those sediments were measured and calculated.
Lab Results
The sample results for porosity and effective porosity are presented in Table 4-1
below. The effective porosity values were used to calculate the specific yield of the
meadow. The results for effective porosity are within the expected range based on other
reported results for the type of sediment present. The results for total porosity were
higher than expected and may be indicative of laboratory error.
Table 4-1: Porosity results
Sample ID
Depth
(ft bgs)
Total Porosity ASTM
D425 (%Vb)
Effective Porosity
ASTM D425 (%Vb)
SO-VVM-101510-SB-20-2.2
1.7- 2.2
71.4
35.8
SO-VVM-101510-SB-20-2.8
2.3 - 2.8
53.9
26.7
Notes: ft bgs = ft below ground surface
Vb = Bulk volume
Sample orientation was vertical
Table 4-2 presents a summary of the particle size results, which were also
consistent with field observations. The particle size distribution confirmed field
54
observation in that the top two ft consisted of silty sediments and the sample below two
ft consisted of a medium sand.
Table 4-2: Grain size results
Mean Grain
Size
Median
Grain
Size
Particle Size Distribution, weight percent
Silt
Sample
Depth,
ft.
Description
mm
Gravel
Coarse
Medium
Fine
Silt
Clay
Clay
1.7-2.2
Silt
0.021
0.00
0.00
3.45
14.58
66.33
15.64
81.97
2.2-2.8 Medium sand
0.390
0.00
5.86
41.54
Notes: (1) Mechanical sieve does not differentiate silt clay fractions
42.36
(1)
(1)
10.24
Sand Size
&
Determining the Volume of Meadow Sediments
Seismic surveys were performed to estimate the depth of bedrock throughout the
meadow (Figure 3-3). Figure 4-1 presents the areas and average depths derived from
Figure 3-3. The seismic refraction data tables and graphs for each survey location are
presented in Appendix A. A summary of the calculated velocities and bedrock depth are
presented in Table 4-3 below.
Table 4-3: Compiled seismic survey velocities and estimated bedrock depths
Survey
Number
Velocity
(ft/s)
S-01A
3,279
S-01B
V1
Velocity
(m/s)
V1
Velocity V2
(ft/s)
Velocity V2
(m/s)
Estimated Depth
to Bedrock (ft)
1,000
16,111
4,914
8.1
2,900
885
19,600.00
5,978
10.0
S-02A
--
--
--
--
--
S-02B
--
--
--
--
--
S-03A
2,466
752
16,701
5,094
7.8
55
Table 4-3 (continued)
Survey
Number
Velocity
(ft/s)
S-03B
4,051
S-04A
V1
Velocity
(m/s)
V1
Velocity V2
(ft/s)
Velocity V2
(m/s)
Estimated Depth
to Bedrock (ft)
1,235
18,974
5,787
12.9
667
203
16,400
5,002
7.7
S-04B
960
293
20,800
6,344
11.5
S-05A
1,600
488
9556
2,914
3.4
S-05B
1,500
458
9500
2,898
3.8
S-06A
--
--
--
--
--
S-06B
--
--
--
--
--
S-07A
1,909
582
17,667
5,388
9.4
S-07B
1,159
354
17,263
5,265
7.5
S-08A
1,500
458
17,647
5,382
13.8
S-08B
1,682
513
17,875
5,452
16.8
S-09A
1,500
458
20,625
6,291
7.0
S-09B
2,222
678
20,000
6,100
8.9
Average
1,957
597
17,051
5,201
9.2
Minimum
667
203
9,500
2,898
3.4
Maximum
4,051
1,235
20,800
6,344
16.8
Meadian
1,641
500
17,657
5,385
8.5
-- Indicates unreliable data and was not used to estimate bedrock depth
The velocities are generally consistent with known bedrock and alluvium
velocities (Burger, 1992). The velocity through the first layer (alluvium) at seismic
survey S-04 is slower than the other velocities through the first layers. This may be due
to the lack of moisture at the location of seismic survey S-04. Groundwater level at all
other locations was relatively close to the surface.
56
Based on the estimated depths, approximately 17.5 acres of the meadow have an
average depth to bedrock of 2.5 ft, 26.6 acres have an average depth of 7.5 ft, and 17.3
acres have an average depth of 12.5 ft. The total area of the meadow is 61.4 acres. These
areas were found by highlighting the areas shown in Figure 4-1 using the common wand
tool in Photoshop CS5. The total volume of the meadow in cubic meters was calculated
using the equation shown in Table 4-4 below. The calculation gives an estimated
volume of 86.98 af or 107,284.06 m3 of total sediment in the meadow.
Table 4-4: Calculating the volume of sediments in the meadow
V = (A1D1+ A2 D2 + A3 D3)(233.48 m3/af)
= ((17.5 acres * 2.5 ft) + (26.6 acres * 7.5 ft) + (17.3 acres * 12.5 ft) (233. 48m3/af)
= (43.75 af + 199.50 af + 216.25 af)( 233. 48 m3/af)
= 459.5 af * 233.48 m3/af
= 107,284.06 m3
Where,
A1
= Area with average bedrock depth D1
= 17.5 acres
D1
= Average bedrock depth in area A1
= 2.5 ft
A2
= Area with average bedrock of D2
= 26.6 acres
D2
= Average bedrock depth in area A2
= 7.5 ft
A3
= Area with average bedrock of D3
= 17.3 acres
D3
= Average bedrock depth in area A3
= 12.5 ft
Note:
3
233.48 m = 1 af
Calculating the Specific Yield of the Meadow
In order to calculate the specific yield of water in the meadow, the volume of
sediment was converted to acre-ft (af) of sediment and multiplied by the effective
57
porosity attained from lab analysis. Based on field observations from 21 soil borings, the
sample collected within the top two feet in soil boring SB-20 is representative of the top
two ft of soil throughout the meadow. The effective porosity from this sample collected
in the silty zone had an effective porosity of 35.8% and was used to calculate the
specific yield of the sediments within in the top two ft of the meadow.
The specific yield of the sediments between two and five ft was calculated using
an effective porosity of 26.7%, which was based on the sample collected from soil
boring SB-20 in the medium sand zone from 2.2 to 2.8 ft bgs. This sample appeared to
be representative of the soil in the meadow from two ft until refusal was met
(approximately five to six ft) while hand auguring. The sediments below refusal have
not been observed and therefore the effective porosity of the sediments below this point
is not definitively known. The sediments at depth in the meadow are likely coarser
grained than the surface sediments, including coarse gravel, cobbles, and boulders. The
mean effective porosity for coarse gravel is 21% (McWorter and Sunada, 1977).
Therefore, the deeper sediments from 5 ft to bedrock were estimated to have an effective
porosity of 21%. It is reasonable to assume that the alluvium at depth is coarser than
sediments at the top of the meadow just below the root mass. Table 4-5 below
summarizes the calculation of the specific yield of the meadow.
58
Table 4-5: Calculating the specific yield of the meadow
Sy = (Vtop* Øtop ) + (Vmiddle * Ømiddle) + (Vbottom * Øbottom)
= (153.5 af * 0.358) + (109.8 af * 0.267) + (43.3 af * 0.21)
= 55af + 29.3af + 9.1af
= 93.4 af
Where,
Sy = specific yield of the meadow
Vtop
= volume from 0 to 5 ft
= (A1+A2+A3) * H1
= (17.5 acres + 26.6acres + 17.3acres ) * 2.5 ft
= 61.4 acres * 2.5 ft
=153.5 af
Vmiddle
= volume from 5 to 10 ft
= (A2+A3) * H2
= (26.6+17.3) * 2.5 ft
= 43.9 acres * 2.5 ft
= 109.8 af
Vbottom
= volume from 10 to 15 ft
= A3 * H3
= 17.3 acres * 2.5 ft
= 43.3 af
Øtop
= effective porosity of top 2.5 ft
= 35.8%
Ømiddle
= effective porosity from 2.5 to 7.5 ft
= 26.7%
Øbottom
= effective porosity from 7.5 to 12.5 ft
= 21%
A1
= area with average depth of 2.5 ft to bedrock
= 17.5 acres
A2
= area with average depth of 7.5 ft to bedrock
= 26.6 acres
A3
= area with average depth of 12.5 ft to bedrock
= 17.3 acres
H1
= average change in depth from 0 to 5 ft
= (5ft – 0ft)/2 = 2.5 ft
H2
= average change in depth from 5 to 10 ft
= (10ft – 5ft)/2 = 2.5 ft
H3
= average change in depth from 10 to 15 ft
= (15ft – 10ft)/2 = 2.5 ft
The area measurements are shown on Figure 4-1. The specific yield of the
meadow is estimated to be approximately 93.4 af of water if the meadow is fully
59
saturated. If the water level in the meadow is 2.5 ft bgs, which it is for some of the year,
specific yield would be estimated at approximately 38.4 af (93.4 af – 55 af).
Limitations of Determining the Effective Porosity
Because the majority of sediments in the meadow were not accessible by hand
auger, there are limitations to the estimate of specific yield within the deeper zone of the
meadow. Hand auguring presented a limited view of the types of sediments that are
present. However, general assumptions can be made about the effective porosity given
the location and types of material observed. Depending on the effective porosity of the
deeper sediments, the volume of water stored in the meadow could vary. An effective
porosity value of 21% was used for the deeper sediments, but if it varied greatly the
potential volume of water in the meadow would potentially vary as well. Although it is
important to acknowledge that a range of effective porosities could exist, the values used
in Table 4-5 were the most accurate based on samples collected given that the sediments
at depth are slightly coarser than sediments at the surface.
4.2 Groundwater Fluctuations
Water pressure and temperature data were automatically collected every 20
minutes by pressure transducers and stored on data loggers during the study period.
After downloading the data, the data were averaged for each day for each location. The
daily pressure value was converted to ft of water by multiplying the value by 2.31 ft/psi
(one pound per square inch is equal to 2.31 ft per one pound per square inch). Graphs
60
that include the daily recorded pressures and temperatures are presented in Appendix E.
Table 4-6 below shows the average water levels for all piezometers during four different
periods including October 24 through December 31, 2009, January 1 through March 31,
2010, April 1 through June 30, 2010, and July 1 through October 23, 2010. The periods
were selected based on natural trends that were apparent when initially analyzing the
data. Figure 4-2 presents the data from Table 4-6 in graph format.
Table 4-6: Average groundwater level data
October 24 - December
January 1 - March
April 1 - June 30,
July 1 - October
31, 2009
31, 2010
2010
23, 2010
PZ-01
0.43
0.4
0.02
2.73
PZ-03
0.83
0.36
0.29
1.89
PZ-04
1.15
0.29
-0.12
1.36
PZ-05
1.3
0.44
0.56
0.95
PZ-06
0.89
0.71
0.31
0.37
PZ-07
2.82
2.79
1.63
0.92
PZ-08
-0.36
-0.53
-0.66
0.03
PZ-10
0.58*
0
-0.29
1.37
PZ-11
----PZ-12
0.69
0.39
0.7
1.22
PZ-13
1.43*
1.03
0.86
2.9
Notes: Water level measurements are shown in ft below ground surface (the negative values indicate
water level above ground surface).
* November 15, 2009 through December 31, 2009
-- Inconclusive data
Limitations
Some of the short-term fluctuations of water levels were due to equipment
malfunctions. The averaging of several months limited the effect of shorter-term errors.
The averaged data appear to be representative of conditions based on field observations.
61
If a cold snap occurred when water level was close to surface ice may have plugged the
top of the piezometer, which may have influenced the pressure readings. The
groundwater levels tended to quickly fluctuate several ft when temperatures dropped
near freezing. The short-term fluctuation recorded is likely related to the water freezing
and ice thawing at the surface rather than actual fluctuations in water level.
Because of the above-mentioned limitations, any single minimum or maximum
groundwater level reading may not be representative of the actual water level.
Therefore, comparing minimum and maximum readings from a single point in time at
all locations is not useful in determining hydrologic functions of the meadow. However,
some important general trends should be noted. Typically, the water levels increased
from the time the piezometers were installed (October or November 2009) to May 2010.
Water level was at ground surface or within one foot of ground surface in most
piezometers during this period. Groundwater level increased to the highest level in most
piezometers during the April 1 to June 30, 2010 period. This increase was likely due to
the influx of water from snow melting as air temperatures increased. Groundwater levels
begin to decrease by early July 2010. The temperature of groundwater at all locations
abruptly increased between June 9 and 13, 2010.
Piezometer PZ-08 recorded noticeably higher water levels compared to the other
locations because it is located in a low and relatively flat area that drains more slowly
than the other areas. Field observations indicate that ground water levels were above
62
ground surface in few piezometers for some of the year. Piezometer PZ-07, which is
located 3.4 ft higher and to the east of piezometer PZ-08, recorded the lowest water
levels compared to all other piezometers during the first three periods. Piezometer PZ-07
also showed the sharpest climb in water level from the second period to the third period.
Piezometer PZ-06 is located at a slightly higher elevation than the other surrounding
piezometers in the north part of the meadow (PZ-01 though PZ-05) and the water level
was slightly lower here as expected.
All data trends agree with field observations with exception of piezometer PZ05. Readings from piezometer PZ-05 were elevated beyond a realistic level. Based on
visual observations, the water level was noted as being six inches higher on the outside
of the piezometer (in the annulus between the piezometer and the native soil) compared
to the inside of the piezometer. The screen may have become blocked when the water
level was depressed and the water was subsequently unable to drain into the piezometer
when the surrounding water level increased. The data points were corrected to a
practical level based on manually recorded water level measurements at Piezometer PZ05. Piezometer PZ-11 was not included in the groundwater level measurements due to
equipment malfunction. Piezometers PZ-02, PZ-09, PZ-14, and PZ-15 did not contain
transducers.
63
4.3 Surface Water Level Data
Surface water level data included the data collected from the eastern inflow,
western inflow, northern inflow, and the outflow weirs. Water pressure and temperature
data were automatically collected every 20 minutes by pressure transducers and stored
on the built-in data loggers during the study period. After downloading the data, the data
were averaged for each day for each location. In order to convert the recorded pressure
in pounds per square inch to ft of water, the daily pressure value was multiplied by 2.31
ft/psi. Drastic short-term fluctuations of water level (20 minutes to 1 hour timescale)
were most likely due to equipment sensitivity and turbulence. The water flowing past
the piezometer can be very turbulent during times of high flow and may have
contributed to the unrealistic fluctuations in pressure readings. Even though the pressure
readings were averaged over an entire day, sporadic results due to turbulence appear to
have still skewed the data. Visual observations and manual water level measurements
were used to calibrate the water levels converted from the recorded pressure.
The following sections discuss the estimated water levels and calculated
discharge for the outflow weir and overflow channel as well as the inflow weirs. The
height of the water level above the notch in the weir was used to calculate the discharge
using the equation Q = 2.49h12.48 where Q is the discharge over the weir (ft3/s) and h1 is
the head on the weir (ft).
64
Water level and temperature data as well as discharge and temperature data were
graphed for each location and are presented in Figures 4-3 through 4-15 and are
discussed in the following sections. Table 4-7 presents the average daily discharge for
the same four periods addressed in the Section 4-2. The daily average discharge was
used for comparing each period because each period is not equal. The first period is
shorter than the other periods and the last period is longer than the other periods.
Table 4-7: Average daily discharge (af/day)
Period and days
Outflow
Overflow
Daily
Outflow
Eastern
Western
Northern
Daily
Inflow
October 25 - December
31, 2009 (67 days)
3.08
0.00
3.08
3.15
0.11
3.07
6.33
January 1 - March 31,
2010 (89 days)
18.61
3.55
22.17
10.43
0.42
4.15
15.00
April 1 - June 30, 2010
(90 days)
42.28
18.81
61.09
45.62
7.09
6.99
59.94
July 1 - October 24, 2010
(115 days)
4.52
0.00
4.52
2.75
0.17
0.45
2.57
The results for each location shown in Table 4-7 are discussed individually in the
following sections. It is important to note that the inflow values presented in Table 4-7
are only considering inflow via surface water, while the outflow weir tracks all water
exiting the meadow (whether it was surface water inflow or precipitation as rain or
snowmelt). Precipitation and slope run-off are discussed in the water budget in a later
section. Overall, the outflow daily rate exceeded the total daily rate of surface water
inflow during three of the four periods. The highest discharge rate for both surface water
65
inflow and outflow occurred during the third period, from April 1 through June 30,
2010. The lowest outflow discharge rates occurred during the first period from October
25 through December 31, 2009, while the lowest inflow discharge rates occurred during
the last period from July 1 through October 24, 2010. Surface water daily inflow
exceeded outflow during the first period from October 25 through December 31, 2009.
Prior to downloading the data, it was expected that short-term fluctuations in
water level would be comparable between each location and conclusions could be made
about the residence time of water in the meadow. It was expected that inflow discharge
peaks would occur at distinct time before the outflow peak would occur and the
difference in time between would indicate residence time. These expectations were not
fully met in that the short-term peaks were somewhat indefinable, possibly due to
turbulence in the culverts. Because the pressure transducers are very sensitive
instruments, small amounts of turbulence in the water passing through the weirs can
affect the readings. Based on field observations, turbulence increased as water level
increased. However, some distinct peaks were visible and were used to estimate
residence time of water in the meadow. Water flowing through each inflow weir has a
different residence time based on the distance from the outflow weir. The timing of the
peak discharge from each inflow weir was compared to the timing of the peak discharge
from the surface water outflow weir and overflow channel to find the residence time of
water from the inflow weir. Residence time is discussed in Section 4.7 following
individual discussions regarding each weir.
66
In terms of total volume, the total surface water inflow was greater than the total
surface outflow for the first period, as shown in Table 4-8 below. The total outflow
discharge was greater than the inflow discharge during the other periods. As expected,
the period from July 1 through October 24, 2010 experienced the lowest amount of total
inflow, when snowmelt run-off was almost non-existent because the majority of snow
had already melted. The total inflow via surface water locations during the entire study
period is less than the total surface water outflow, which was expected because other
input factors such as precipitation and slope run-off were not included in the above
comparison. The other factors of the water budget will be discussed in Section 4.6.
Table 4-8: Calculating the surface water inflow and outflow
Input (af)
Surface Water
Location
October 25 December 31, 2009
January 1 - March
31, 2010
April 1 - June 30,
2010
July 1 - October 23,
2010
Total
Output (af)
Eastern
Western
Northern
Total
Input
214.4
7.5
208.8
430.7
209.7
0
209.7
938.6
37.8
373.9
1,350.3
1,675.1
319.9
1,995.0
4,151.3
645.3
635.6
5,432.3
3,847.4
1711.5
5,558.9
312.5
18.8
51.4
382.7
514.8
0.5
515.3
5,616.8
709.4
1269.7
7,596
6,247.0
2,031.9
8,278.9
7,595.9
Outflow
Overflow
Total
Output
8,278.9
4.3.1 Outflow Culvert and Overflow Channel
Pressure readings were based on the level of the transducer to be 0.3ft above the
base of the culvert. This elevation is equivalent to the center of the notch on the weir
67
(0.4ft from the base of the culvert with the slope of the culvert adding 0.1ft at the
location of the transducer). The data points were adjusted based on manual
measurements taken throughout the study period.
Based on the discharge calculations and water level observations, approximately
6247 af of water discharged through the outflow culvert over the course of the study
period. Figure 4-3 presents the water levels (before and after calibration) used to
calculate the discharge of the outflow weir and the overflow channel. The graph
presented in Figure 4-3 shows the water level that was originally calculated from the
calibrated pressure readings. The calculated water level was adjusted based on visual
observations to find the adjusted water level. The water level was corrected based on
field observations of deposition and high water marks to result in the actual water level.
The highest water level possible was 2.4 feet in the culvert and the actual water level
represents this shown on Figure 4-3.
Figure 4-4 presents the calculated discharge from the outflow weir and from the
overflow channel. Figures 4-5 and 4-6 show the combined discharge of the outflow weir
and overflow channel compared to the water temperature and precipitation measured at
the Van Vleck Station.
The data indicate that the flow gradually increased during the late fall through
the winter of 2009/2010. In late March 2010, the flow increased again as air
temperatures and snowmelt run-off increased. The recorded data indicate that the
68
highest flow occurred from late March through June 2010. Flow generally began to
decrease in July 2010 during the relatively dry summer months until precipitation
increased again in October 2010. The increase in water temperature as shown on Figure
4-5 is also a function of an increase in baseflow, which would contribute water that is
warmer than snowmelt.
Piezometer Breakage
On June 8, 2010, the piezometer in the outflow culvert broke and the measuring
point level changed from 0.3ft above the culvert base to 0.7ft above the base of the
culvert. This change in level was verified by visual observation on June 26, 2010. The
0.4ft change (0.7 ft – 0.3 ft) was factored into the remaining data points that were
affected after June 26, 2010. Figure 4-3 shows the water levels before they were
corrected for the change in elevation.
Compensating for Unrealistic Pressure Increase
The total pressure climbed to unrealistic values after the outflow culvert
piezometer broke. Water turbulence could have caused the transducer to tap against the
bottom of the culvert or against debris flowing through the culvert. Bernoulli’s Effect
created by water flowing past the unprotected transducer may have also been a factor in
inconsistent readings. Although the data were corrected for a 0.4 ft change in the
measuring point, the pressures recorded after the breaking of the piezometer were
unrealistic. When compared to visual observations, the total pressure values recorded
69
after the breaking point appeared to be elevated by approximately four psi, which is
equivalent to 9.24 ft of water (4 psi * 2.31 ft/psi). The water levels recorded after the
breakage were elevated values, however, the time in which general changes in level
occurred may be considered valid. To compensate for the elevated readings, 9.24 ft was
subtracted from water level readings from June 8 to July 3, 2010 when another water
level measurement was manually recorded to calibrate the water level data.
By reducing the water level values by 9.24 ft after the piezometer breakage, the
levels are more consistent with actual water levels manually recorded. The actual water
level after corrections is also presented in Figure 4-3.
4.3.2 Overflow Channel
The overflow channel is located on the upstream side of the culvert where the
outflow weir is constructed. The overflow channel allows water to overflow onto the
road and return to the creek downstream of the outflow weir. When water flowed
through the overflow channel and flooded over the road, it missed the weir and gauging
equipment. Based on surveyed elevations of the channel and outflow weir, water began
to flow though the overflow channel when the water level above the weir reached 1.65
ft. Figure 2-10 presents a conceptual drawing of the overflow channel and the outflow
weir. Plant and soil disturbance as well as recently deposited debris confirm the
maximum height of water that flowed through the overflow channel during the study
period.
70
It is reasonable to assume that the water level in the channel and the culvert
increased in the same increments while overflow occurred (water levels greater than
1.65 ft). Based on the high water marks at 0.75 ft in the channel, the highest water level
in the culvert would have been 2.4 ft (1.65 ft + 0.75 ft). A summary of the calculations
for estimating how much water potentially flowed through the overflow channel are
shown below in Table 4-9. The detailed calculations for finding the total overflow
channel discharge are shown in Appendix F.
Table 4-9: Calculating overflow channel discharge during the high flow
Q = (1.0/n)A(R2/3)(S1/2) = (1.0/0.035)( 0.966)(0.1152/3)(0.0041/2)
= (28.6)(0.966)(0.236)(0.063)
= 0.4 m3/s
= (0.4 m3/s)(70.05af/day) = 30.4 af/day
Where,
Q
= discharge, m3/s
A
= cross-sectional area of channel
= 0.966 m2
S
= bottom slope of channel
= 0.004
n
= Manning roughness coefficient, for coarse gravel with
cobbles (Cowan, 1956)
= 0.035
R
= hydraulic radius = A/P
= 0.115 m
P
= wetted perimeter of cross-sectional flow area
= 8.42 m
y
= height of the overflow area
= 0.21 m
b
= base of the overflow area
= 0.8 m
T
= top of the overflow area
= 8.4 m
The maximum estimate of daily discharge shown above was calculated at 30.4
af/day (when the water level reached 2.4 ft at the weir). The high water level mark was
71
identified by debris and soil erosion evidence in the channel and across the road. The
discharge values for flows less than the maximum were calculated using three other
water levels including 2.2 ft, 2.0 ft, and 1.82 ft. These three water levels were chosen
because they are relatively evenly spaced heights to estimate the discharge during
different periods. These water levels measured at the outflow weir produced 21.5 af/day,
13.6 af/day, and 0.5 af/day of flow through the overflow channel, respectively. Table 410 below presents the discharge values used for specific ranges in water level height.
Table 4-10: Estimating overflow discharge from water level
Water Level
above Weir
(ft)
Calculating Water
Level in Overflow
Channel (ft)
Water level
in Overflow
Channel (ft)
Water Level
in Overflow
Channel (m)
Discharge
(af/day)
Estimating
discharge for
water level
readings
2.4
2.4 - 1.65 = 0.75
0.75
0.23
30.40
>2.3 ft
2.2
2.2 - 1.65 = 0.55
0.55
0.17
21.50
2.1 to 2.3 ft
2.0
2.0 - 1.65 = 0.35
0.35
0.11
13.60
1.91 to 2.0 ft
1.82
1.82 - 1.65 = 0.18
0.17
0.05
0.50
1.65 to 1.9 ft
Approximately 101 days were recorded as having water levels high enough to
produce flow in the overflow channel (a water level greater than 1.65 ft at the outflow
weir). Discharge calculations for the overflow channel are shown in detail in Appendix
F. Based on four ranges of water levels identified in Table 4-9, 30.4 af/day flowed
through the overflow channel for 48 days, 21.5 af/day flowed through the overflow
channel for 21 days, 13.6 af/day flowed through the overflow channel for 8 days, and
0.5 af/day flowed through the overflow channel for 24 days. The total quantity of water
72
that passed through the overflow channel during the study was calculated to be 2,031.9
af.
Limitations
The lack of controls on the overflow channel is a limitation in this study. Debris
flowing through the overflow channel may have obstructed water in the overflow
channel and raised the water level in the culvert. Conversely, debris at the face of the
culvert may have blocked the culvert and increased the water level in the channel. The
discharge estimate is only as accurate as the water levels that were recorded at the
outflow weir because the water levels in the overflow channel are based on the height
measured at the outflow weir.
4.3.3 Eastern Inflow
The average discharge for each of the four periods during the study from the
eastern inflow weir are presented in Table 4-7. Figures 4-7 through 4-9 present graphs of
the water levels, discharge and water temperature, and discharge and precipitation.
Based on the water level observations and discharge calculations, approximately 5,616.8
af of water discharged through the eastern inflow weir over the course of the study
period.
Figure 4-7 shows the water level that was originally calculated from the
calibrated pressure readings. The calculated water level in was adjusted based on visual
observations to find the adjusted water level. The adjusted water level was corrected
73
based on field observations of deposition and high water marks to result in the actual
water level.
The maximum height of water possibly passing through the culvert was
just below 2.54 feet based on high water marks on the upstream side of the culvert. The
adjusted water level contained some readings that were above 2.54 feet. These readings
were modified to 2.54 feet to show the actual water level. The actual water level was
used to calculate the discharge of the eastern inflow weir. The highest adjusted water
level reading at the eastern inflow weir was four feet (Figure 4-7). This reading is
unrealistically elevated due to turbulence and was not representative of the actual
conditions because the height of the culvert is only 2.54 ft and high water marks indicate
water level was just below the top of the culvert. All water levels recorded above 2.54 ft
were likely due to equipment sensitivities and turbulence. Visual observations confirm
that water did not flow around the culvert at this location.
The eastern inflow data indicate that water level and discharge fluctuations
throughout the study period were generally consistent with the outflow water level and
discharge fluctuations. The eastern inflow data indicate a steady but slow increase in
discharge from October 2009 to March 2010 and a steeper increase from March to midMay 2010 (Figure 4-8 and 4-9). The discharge was highest from mid-May through June
2010. The flow decreased more quickly from June to July 2010 and slowly from July to
October 2010. In the beginning of October 2010, the discharge increased again, likely
due to an increase in precipitation.
74
The fluctuations in discharge correspond to temperature (Figure 4-8). As
temperature increases, water level and discharge increase. This is due to snowmelt
runoff from the area upstream feeding the eastern inflow weir. The majority of surface
water enters the meadow from the eastern inflow weir as expected because Tells Creek
flows through this weir. The fluctuations in discharge also correspond as expected to
precipitation (Figure 4-9). Precipitation significantly decreased by May 29, 2010.
Discharge did not decrease until June 18, 2010, 19 days after the cessation of
precipitation. Snow melt contributed to the delay.
4.3.4 Western Inflow
The average discharge for each of the four periods from the western inflow weir
are presented in Table 4-7. Based on water level measurements and the visual
observations, the western inflow weir discharged approximately 709.4 af to the meadow
during the study period. The total discharge is significantly less than the other locations,
as expected. Figures 4-10 through 4-12 present graphs of the western inflow water level,
discharge and temperature, and discharge and precipitation. Figure 4-10 shows the water
level that was originally calculated from the calibrated pressure readings. The calculated
water level was adjusted based on visual observations to find the adjusted water level.
The adjusted water level was corrected based on field observations of the highest
possible water level to show the actual water level. As shown on Figure 4-10, the
highest water level occurred on May 20, 2009 at 1.83 ft. This measurement is not
75
possible because it is higher than the culvert height (1.5 ft) and the highest water level
mark observed was below the top of the culvert. The few measurements that were
recorded higher than 1.5 ft were reduced to the maximum possible height of 1.5 ft, as
shown in Figure 4-10. No evidence of overflow around the culvert was observed. The
water levels in the western inflow culvert were similar to the other locations in terms of
the increases and decreases between the four periods as well as the level of the change.
The highest water levels were observed between late May and early June 2010. The
temperature at this location is notably higher throughout the study period compared to
other locations (Figure 4-11). This is likely due to the southern exposure of the weir and
the lack of vegetation surrounding the water flowing into the culvert that would have
provided shade. There is a possibility that groundwater contributions could be a factor in
causing the higher water temperatures at this location. However, field observations
during the spring, summer, and fall indicate that groundwater is not a likely contributor
at this location. By mid-summer 2010, the western inflow did not contribute water to the
meadow until significant precipitation occurred again in the late fall of 2010.
4.3.5 Northern Inflow
The northern inflow data is consistent with the other weir locations. Based on
water level measurements and the visual observations, the northern inflow weir
discharged approximately 1,269.7 af to the meadow during the study period. The
average discharge for each of the four periods during the study from the northern inflow
76
weir are presented in Table 4-6. Figures 4-13 through 4-15 present graphs of the water
level, discharge and temperature, and discharge and precipitation. Figure 4-13 shows the
water level that was originally calculated from the calibrated pressure readings. The
calculated water level was adjusted based on visual observations to find the actual water
level.
An increase in discharge was observed in the fall of 2009 as shown on Figures 414 (discharge and temperature) and 4-15 (discharge and precipitation). The data indicate
that the discharge increased from 1.53 af/day on December 17, 2009 to its peak of 16.32
af/day on December 23, 2009. The second increase resulted in a discharge increase from
1.25 af/day on January 9, 2010 to 19.07 af/day on January 13, 2010. A four-day
precipitation event that resulted in 6.09 inches preceded the increase on December 21,
2009 by six days. The January 11, 2010 increase occurred eight days after a minimal
precipitation event. The temperature did not increase significantly enough to melt snow
that would have caused an increase in discharge (Figure 4-14). The rain event preceding
the January increase at the northern weir occurred from December 27, 2009 through
January 2, 2010 and only resulted in 2.64 inches of precipitation. The January 11, 2010
increase is not fully explainable by precipitation and temperature data and may be an
anomaly.
An average decrease in discharge occurred from 10.12af/day on March 13, 2010
to 0.11 af/day on April 19, 2010 (Figures 4-14 and 4-15). This may be due to a drop in
77
temperatures during the night and water freezing. During this time period, steady
precipitation occurred. Lower nightly temperatures may have contributed to freezing and
or the majority of precipitation occurs as snow instead of rain. The discharge increased
again after mid April to a peak of 25.04 af/day on June 7, 2010.
When downloading the data on April 24, 2010, the piezometer was manually
pushed one foot further into the ground at the northern weir. This resulted in readings
that were approximately elevated by one foot. The increase in water level was accounted
for by subtracting one foot from the readings for the remainder of the study period.
4.4 Precipitation
Meadow Precipitation
Precipitation data attained from the CDEC website were used to estimate the
approximate amount of water contributed by rain or snow that fell directly on the
meadow. Figure 2-13 presents the precipitation as rain and snow that was recorded at the
Van Vleck Station during the study period. The Van Vleck Station received up to 85.2
inches (7.1 ft) of rain and 46 inches (3.8 ft) of snow as water content during the study
period. The snow values may be low compared to the actual amount that was
contributed to the meadow. Based on visual observations, the Van Vleck Station is
located in a sheltered location, along an eastern slope, compared to the open area of the
meadow. It is possible that more snow was able to accumulate in the open meadow. On
April 24, 2010, field staff manually dug to the ground surface at the northern inflow
78
weir and north of piezometer PZ-06. Both locations resulted in a snow depth greater
than eight ft. Visual observations near the weather station indicate snow levels of only
six ft. The amount of snow recorded at the Van Vleck Station was used as a
conservatively low number for the snow input to the meadow.
The 2.3 acre-area of the meadow that is north of the northern inflow was not
included in estimating the amount of precipitation the meadow received since the rain
and snow that fell in that area was accounted for by the northern inflow weir. The 2.3
acres north of the northern inflow weir was subtracted from the total meadow area. The
meadow area between the weirs was then multiplied by the feet of rain and snow as
water content. As shown in Table 4-11 below, the meadow received approximately
644.9 af of water from precipitation during the study period.
Table 4-11: Calculating snow and rain direct input
Area that received direct rain and snow = total area – area north of weir
= 61.4 acres – 2.3 acres = 59.1 acres
Total direct rain input
59.1 acres * 7.1 ft rain
= 420.1 af
Total direct snow input
59.1 acres * 3.8 ft snow melt
= 224.8 af
Total rain and snow input received by meadow
420.1 af rain + 224.8 af snow melt
= 644.9 af
Slope Run-Off
The contribution of water to the meadow via slope run-off was calculated by
multiplying the area of the slope by 68% of precipitation received. Based on the
estimation of water volume from slope run-off upgradient of the northern weir,
79
approximately 68% of the volume of water that is precipitated on the slope reached the
northern weir. This 68% of rainfall was used to estimate how much water entered the
meadow directly from the slopes surrounding the meadow (the slopes that did not funnel
water through a weir). The total slope area that contributed run-off directly to the
meadow (not via a weir) was estimated to be 163.86 acres. Figure 2-14 presents the
areas where slope run-off likely contributes to the meadow input. As shown in Table 412 below, slope run-off contributed 791.1 af from rain and 423.4 af from snowmelt to
the meadow. The total contribution of slope run-off was estimated to be 1,214.5 af
(791.1 af + 423.4 af).
Table 4-12: Calculating slope run-off
Slope Area (acres)
Contribution from
Precipitation as Rain
(68% * 7.11 ft)
Contribution from
Precipitation as Snow (68% *
3.8 ft)
Northeast
26.28
126.9
67.9
Southeast
57.16
276.0
147.7
Southwest
13.3
64.2
34.4
Northwest
67.12
324.1
173.4
Total
163.86
791.1
423.4
Slope on Map
4.5 Evapotranspiration
Evapotranspitation was estimated using the Monthly Average Reference
Evapotranspiration by ETo Zone (University of California, Davis and California
Department of Water Resources, 1999). The area of the meadow within the weirs, 59.1
acres (61.4 acres – 2.3 acres north of northern weir), was multiplied by the annual
80
evapotranspiration rate of 4.5 ft. Transpiration occurs at its highest levels in this region
from June through September (Lesh, 2010). Evapotranspiration was estimated at 266 af
for the study period (4.5 ft x 59.1 acres).
4.6 Calculating Water Budget
The water budget input and output factors, as well as their contribution amount,
are listed in Table 4-13 below. The total input was approximately 9,455.4 af for the oneyear study period while the total output was approximately 8,555.2 af.
Table 4-13: Calculating change in storage
Change in Storage = Input – Output
Input Factor
Contribution (af)
Output Factor
Contribution (af)
Inflow Weirs
7,596.0
Outflow Weir
6,247.0
Precipitation
644.9
Overflow Channel
2,031.9
Slope Run-off
1,214.5
Evapotranspiration
276.3
Total Input
9,455.4
Total Output
8,555.2
The change in storage is 900.3 af (9,455.4 af – 8,555.2 af). An explanation for
this volume of water must be accounted for in the water budget. In October 2009 before
the meadow became saturated, the average depth to groundwater was 2 to 2.5 ft bgs. If
completely filled, 147.8 af of soil (59.1 acres * 2.5 ft) would account for approximately
52.9 af of water (147.8 af soil * 0.358 porosity value). If 52.9 af were subtracted from
the change in storage, 847.4 af (900.3 af – 52.9 af) would still be unaccounted for. If
847.4 af were spread out over the entire meadow within the weirs (59.1 acres), the water
81
height would be 14.3 ft (847.4 af/ [61.4 acres -2.3 acres]) which is not plausible. It is
plausible that this surplus of 847.4 af identified in the water budget is permeating the
bedrock beneath the meadow alluvium and recharging deeper aquifers. The equivalent
of 847.4 af of water permeating bedrock over an entire year is 2.3 af per day (847.4
af/365 days). The rate of permeability over the entire meadow for 2.3 af is 0.04 ft per
day (2.3 af/59.1 acres), which is plausible.
4.7 Estimating Residence Time Based on Daily Discharge Peaks
In order to calculate the residence time of water in the meadow, the discharge
peaks for the input factors were compared to the discharge peaks of the outflow
locations. As noted earlier, the sensitivity of the transducers combine with turbulence at
the weirs presents a problem drawing comparisons based on one daily reading. For this
reason, most of the discharge peaks are difficult to compare. However, the input and
output peaks and troughs that appeared distinct were compared using the daily data.
Specific peaks that were distinct are shown in Figures 4-16 through 4-18.
A limitation with identifying the residence time of water in the meadow using
the comparison of discharge quantities is that the majority of discharge flows through
the eastern weir via Tells Creek to the outflow weir. The water has a significantly
shorter residence time if starting from the eastern inflow weir compared to the northern
or western inflow weir based on distance and flow path.
82
Figure 4-16 presents a graph comparing the eastern inflow and outflow final
discharge peaks prior to the decline in discharge during the summer months. This
comparison shows that there was a delay of two to three days from the peak or trough of
the discharge passing through the eastern inflow weir to the peak of the outflow weir
and overflow. The initial decrease in discharge from 64.27 af/day to 45.91 af/day
(change of 18.36 af) at the eastern inflow weir occurred on June 17, 2010. The initial
drop in discharge from 86.24 af/day to 31.78 af/day (change of 54.46 af) at the outflow
weir location occurred on June 19, 2010. The change in outflow was more significant
than the change in the eastern inflow and may be accounted for by the decrease in
discharge from the northern and western inflow weirs.
The discharge quantity from the northern inflow weir and western inflow were
significantly less than the discharge quantity from the eastern inflow weir. Figure 4-17
presents the discharge peaks for all surface water inflow and outflow locations prior to
the decrease in discharge that occurred during the summer months. The northern inflow
discharge peak occurred on June 15, 2010 with a discharge rate of 23.15 af/day, which
was four days prior to a decline in discharge at the outflow weir and overflow channel.
The change in discharge was 13.15 af/day (23.15 af/day - 10 af/day) and was somewhat
gradual.
It is important to note that the output quantity used in the comparison above
includes the overflow channel discharge in addition to the outflow weir. As discussed in
Section 4.3.2, the discharge amount of the overflow channel was based on high water
83
marks. Four ranges of overflow discharge quantities were calculated to estimate the
discharge at the outflow locations (0.5 af/day, 13.6 af/day, 21.5 af/day and 30.4 af/day).
Although it would be beneficial in analyzing the output peaks using data collected every
20 minutes, it is impossible given that peaks during the overflow period are based on
general ranges of quantities calculated for the water budget. The increase and decrease
in flow occurs as steps from 0.5 af/day to 13.6 af/day, and from 13.6 af/day to 21.5
af/day and 21.5 af/day to 30.4 af/day.
The western inflow discharge peak occurred on June 6, 2010 with a discharge
rate of 21.56 af/day, which was 13 days prior to a decline in discharge at the outflow
weir and overflow channel. The discharge peak at the western inflow was not well
defined, gradually decreasing to approximately four af/day two weeks after the decrease
began. The change in discharge was 17.56 af/day (21.56 af/day – 4 af/day). The gradual
and minimal decrease in discharge from the western inflow weir is problematic in
defining the residence time of water in the meadow. Thirteen days is longer than
expected and it is more likely that the large quantities of water coming from the other
inflow weirs masked the changes that occurred due to the changes in flow at the western
inflow weir.
Regarding the specific peak discharge event discussed above, the decrease in
outflow discharge was 54.46 af. The eastern, northern, and western inflow weirs resulted
in a decrease of 49.07 af (18.36 af, 13.15 af, and 17.56 af). The residence time of water
entering the meadow was estimated to be two to three days through the eastern inflow
84
and approximately four days through the northern inflow weir. The residence time of
water entering through the western inflow weir was unidentifiable. Based on field
observations and the observed flow paths to the outflow weir, the western inflow
residence time does not likely exceed the residence time of the northern inflow wier
discharge. The two- to three-day residence time estimated for water entering the eastern
inflow weir is longer than expected, given the short distance and somewhat direct path
to the outflow weir.
Figure 4-18 compares the peak inflow from precipitation and slope run-off that
occurred on November 23, 2009 with the peak total outflow that followed three days
later. The eastern inflow discharge gradually increased as opposed to increasing
abruptly. The precipitation and slope run-off increase was steep while the outflow
discharge increase occurred over four days. The gradual increase of the outflow weir
discharge is likely due to the gradually increasing discharge from the eastern inflow
weir. The outflow weir showed a total increase in discharge of 12.7 af during the peak
on November 26, 2009. Slope run-off and precipitation contributed 19.06 af, the eastern
inflow weir contributed 5.15 af, and the northern and western inflow weirs combined
contributed 1.42 af prior to the outflow peak. The quantity of water entering the meadow
(25.63 af) is greater than the quantity leaving (12.7 af). This indicates that some of the
water that flows into the meadow is contributing to saturating the meadow. The total
input to the meadow (surface water, precipitation, and slope-slope run-off) is slightly
85
greater than the total output (excluding evapotranspiration, which was negligible during
this time of year if existent at all).
Figure 4-19 presents a graph showing the total input and total output (excluding
evapotranspiration). Evapotranspiration is minimal and was not included on this graph
as a daily rate. However, evapotranspiration was factored into the water budget as a total
value for the four months that it would have realistically contributed to the water budget
during study period. As shown in Figure 4-19, total output exceeded total input from
March mid-May and late June through the end of summer 2010. The total input is
greater than total output from October 2009 through part of March 2010 and from late
May through June 2010. These values were based on daily averages of 72 readings
collected.
4.8 Short-Term Fluctuations in Water Level
Even though the daily outflow discharge peaks were unable to be compared to
the inflow discharge peaks during periods of relatively high flow (when water flowed
through the overflow channel), a four-day period prior to high flow conditions was
examined using the water level data recorded in 20-minute intervals. Figure 4-20
presents peak water levels during a four-day period from November 21 through
November 24, 2009. During this period, 1.57 inches of rain occurred. The precipitation
data were recorded as daily values so the exact timing of the peak of the rain event is
unknown, which is a limitation when examining water levels on a short time scale. The
86
analysis of water levels recorded in 20-minute intervals during a rain event show the
timing in which water level peaks occurred at each weir due to precipitation.
The incremental precipitation recorded at the Van Vleck Weather Station
indicated that the meadow received 1.2 inches on November 22, 2009 (12 am to 12 pm)
and 0.55 inches on November 23, 2009 as shown in Figure 4-20. Arrows identify the
peaks used to examine the short-term fluctuations in water level during the period of
interest.
As shown on Figure 4-20, the outflow water level peaks occur later than the
inflow water level peaks. Generally, the water level at the outflow weir increases due to
precipitation in the meadow, slope run-off or other inflow sources (northern, eastern,
and western inflow weirs). During this period, the northern outflow peaks occurred four
hours and 40 minutes (November 22, 2009 12:40 to 17:20) to six hours and 20 minutes
(November 23, 2009 11:00 to 17:20) before the outflow peak occurred. This does not
suggest that the water entering the meadow out the northern inflow weir reached the
outflow weir in four hours and 40 minutes to six hour and 20 minutes. This suggests that
an increase in water level due to precipitation and slope run-off up gradient of each weir
occurs at the northern inflow weir four hours and 40 minutes to six hours and 20
minutes prior to the increase in water level at the outflow weir. The increase in water
level due to precipitation and slope run-off up gradient of the western inflow weir occurs
87
four hours (November 23, 2009 14:20 to 18:20) to five hours and 20 minutes (November
24, 2009 13:00 to 18:20) before the increase in water level at the outflow weir.
The increase in water level at the eastern inflow weir is more gradual and the
peaks are less defined compared to the peaks at the other inflow weirs. One distinct peak
identified in Figure 4-20 occurred 20 minutes prior to the peak at the outflow location
(November 24, 2009 18:00 to 18:20). The outflow peak on November 24, 2009 at 18:20
follows an 18-hour period of no rain (the last rain recorded was on November 23, 2009
which leaves up to 18 hours of no rain). The western inflow shows a water level peak
five hours and 20 minutes prior to the outflow location. The outflow peak that occurs on
November 24, 2009 at 18:20 may be due to the increase in water level at the eastern
inflow (increase in discharge) and not due to the influence of rainfall immediately up
gradient of the outflow weir as potentially indicated by the other two peaks.
The western inflow water level peaks are steeper than the peaks from the
northern or eastern inflow weirs (Figure 4-20). It is expected that the western inflow
peaks would decrease more quickly than the other locations because the slope run-off
area up gradient of the western inflow is much smaller than the slope run-off area for the
northern and eastern locations. The eastern inflow water level peaks are much more
muted than the other inflow locations, likely due to the fact that the eastern inflow weir
is supplied by Tells Creek and a spring upstream. The slope run-off area up gradient of
the eastern inflow is much greater than both the northern and western inflow weirs. The
88
outflow water level peaks in the four-day period appear to have a relatively gradual
decrease in water level following a peak compared to the western and northern inflow
water level peaks. This gradual decrease in water level at the outflow weir may be due to
the continued gradual increase in water level at the eastern inflow weir. In addition,
peaks at the northern and western inflow weirs occur in steps where each peak is slightly
higher than the last, indicating a general increase in flow during the four-day period
presented in Figure 4-20.
Essential, this four-day study indicates that the outflow location responds more
slowly to precipitation and slope –run compared to the northern and western inflow
locations. The peaks of the eastern weir are less noticeable compared to other locations
as expected for the reasons listed above.
Limitations
The limitation in the four-day analysis is the precipitation data, recorded on an
daily basis. The peaks can be related to the precipitation within a 24-hour period. For
instance, the first water level peak examined at the outflow location occurred on
November 22, 2009 at 17:20. According to the precipitation data, 1.2 inches of rain
occurred during November 22, 2009. It is unknown whether the precipitation event
started at 12:00AM on November 22, 2009 or if it started only an hour before the water
level peak occurred at the outflow weir. Short-term comparisons are possible only
89
between the outflow and inflow weirs because the water level data were recorded on 20minute intervals.
It is important to note that the pressures recorded in 20 minute intervals (shown
in Figure 4-20) underwent several calibrations and adjustments to reach daily averaged
data to calculate the water budget and examine peak flow days. The water levels
presented in Figure 4-20 were not adjusted based on field measurements, observations,
and were not adjusted based on the highest possible flow. This four-day analysis of data
recorded at short time interval and was only intended to assess the response time of
water levels. Since the data in Figure 4-20 did not undergo calibration at the same level
as the other data sets, there is expected to be some differences in the appearance of the
graph. The water levels presented in Figure 4-20 should be viewed as a comparison of
timing and not as a comparison of height (quantity).
90
4.8 Figures
Figure 4-1: Calculating meadow volume
91
Figure 4-2: Average groundwater levels
The groundwater levels during each time period are shown in the figure as ft below
ground surface. The water levels typically fluctuate up to 2.5 ft during the study period.
The water levels were recorded in feet below ground surface and the negative values
indicate water level above ground surface.
92
Figure 4-3: Outflow water levels
This graph shows the water level that was originally calculated from the calibrated pressure readings. The calculated water
level was adjusted based on visual observations (squares) to find the adjusted water level. The point at which the piezometer
likely broke is shown by the arrow. The water level was corrected based on field observations of deposition and high water
marks to result in the actual water level.
92
93
Figure 4-4: Outflow weir and overflow channel discharge
This figure presents the discharge from the weir and the overflow calculated from the water level presented in Figure 4-3.
The combine discharge is the total discharge passing through the weir and the overflow channel.
93
94
June 17, 2010 - Decrease in
discharge
May 18, 2010 Increase in water
temperature
Figure 4-5: Outflow discharge and temperature
The total outflow discharge is graphed with the temperature of the water passing through the weir. Notice the increase in
temperature starting on May 18, 2010 and the decrease in discharge starting June 17, 2010. The one-month delay between
increasing temperatures and decreasing discharge occurs as the last of the snow pack melts and excess water leaves the
meadow. The temperature increase is a function of baseflow contributing water that is warmer than snowmelt.
94
95
Figure 4-6: Outflow discharge and precipitation
This graph presents the total outflow discharge and precipitation. Note the decrease in precipitation starting on May 29, 2010
and the decrease in discharge on June 17, 2010. There is a delay of 19 days where precipitation as rain stops and discharge
continues at the same rate. Some of this continuation is due to the snow pack melting. By June 20, 2010 the snow has melted
and is no longer a source of water to be discharged from the meadow. Discharge as baseflow continues through the summer
as shown.
95
96
Figure 4-7: Eastern inflow water levels
This graph shows the water level that was originally calculated from the calibrated pressure readings. The calculated water
level in blue was adjusted based on visual observations to find the adjusted water level. The adjusted water level was
corrected based on field observations of deposition and high water marks to result in the actual water level.
96
97
Figure 4-8: Eastern inflow discharge and temperature
Note the correlation between temperature increasing in late spring 2010 and a high discharge quantity, which is likely due to
snow melting and providing an influx of water.
97
98
Figure 4-9: Eastern inflow discharge and precipitation
98
99
Figure 4-10: Western inflow water levels
This graph shows the water level that was originally calculated from the calibrated pressure readings. The calculated water
level was adjusted based on visual observations to find the adjusted water level. The adjusted water level in blue was
corrected based on field observations of the highest possible water level to show the actual water level.
99
100
Figure 4-11: Western inflow discharge and temperature
100
101
Figure 4-12: Western inflow discharge and precipitation
101
102
Figure 4-13: Northern inflow water levels
This graph shows the water level that was originally calculated from the calibrated pressure readings. The calculated water
level was adjusted based on visual observations to find the actual water level. All are shown in this figure.
102
103
Figure 4-14: Northern Inflow discharge and temperature
103
104
Figure 4-15: Northern Inflow discharge and precipitation
104
105
Figure 4-16: Discharge peak comparison – eastern inflow and outflow discharge
105
106
Figure 4-17: Discharge peak comparison – surface water
The graph above shows compares the timing of the last day of peak flow before decreasing during the summer months. Note
the flat level of the eastern inflow weir and output is due to the water level correction based on visual observations and
manual measurements during periods of high flow.
106
107
Figure 4-18: Peak discharge comparison – November, 2009
There is a three-day delay between the peak of precipitation and slope run-off to the discharge peak of the total output.
107
108
Output generally exceeded input
Figure 4-19: Total input and total output
Notice the total input is generally greater than total output from October 2009 through part of March 2010 and from late May
through June, 2010. Total output exceeds total input generally from late March through late May 2010 and from late June
through October 2010.
108
109
Figure 4-20: Short term water level readings
The graph above shows the fluctuations in water level using 20-minute intervals at each weir from November 21, 2009 at
12AM through November 24, 2009 at 12PM. Precipitation was recorded daily (squares).
109
110
Chapter 5
CONCLUSIONS
The purpose of this study was to define flood attenuation properties, estimate
storage capacity, and develop a water budget for the Van Vleck Meadow. Understanding
the quantity and timing of water entering and leaving the meadow assisted in
quantifying how the meadows aid in flood attenuation. Even though this study was
intended to address flood attenuation and groundwater storage only in relation to the
Van Vleck Meadow, the general results may be true for other meadows of similar size
and location.
The total input and output volumes were calculated to be 9,455.4 af and 8,555.2
af, respectively. Based on these values, the change in storage during the study period of
one year was 900.3 af. Approximately 52.9 af were accounted for by saturating the top
2.5 ft of the meadow leaving 847.4 af unaccounted. This quantity of water is accounted
for as groundwater recharge at a rate of 0.04 ft per day across the 59.1-acre area.
The estimates of inflow and outflow attained in this study confirm that the
meadow does aid in flood attenuation and may lessen the severity of the dry season by
slowly providing water as baseflow downstream. The water budget determined that the
total input exceeded total output from October 2009 through most of March 2010 and
from late May through June 2010. Total output exceeded total input generally from late
March through late May 2010 and from late June through October 2010. Approximately
two af/day discharged through the outflow weir from July through half of September
2010. This quantity of water may seem minute when compared to the largest quantity
111
discharging during the spring. However, two af/day for three months provides a total of
180 af downstream when other water sources such as precipitation were limited or did
not exist.
Short-term discharge peaks of water flowing into and out of the meadow were
difficult to analyze due to equipment sensitivities and other environmental factors, but
the general trends of discharge indicate that the meadow does aid in flood attenuation
and that the meadow does provide water downstream when inflow sources are limited.
The residence time of water in the meadow based on daily averages was estimated to be
two to three days for water entering via the eastern inflow weir and approximately four
days via the northern inflow weir. The residence time of water entering through the
western inflow based on daily averages weir was unidentifiable due to the small
quantities measured. Based on field observations and flow paths observed to outflow
weir, the western inflow residence time does not likely exceed the residence time of
water entering via the northern inflow wier.
Based on the residence times identified in the study, the Van Vleck Meadow
attenuates flood events by slowing the peak of discharge by approximately four days.
This study suggests that the meadow acts as a significant storage space for water and
provides a setting for groundwater recharge in addition to attenuating flood events.
112
APPENDIX A
Seismic Survey Data
113
Figure A-1: Seismic Survey Data for Survey S-01
Geophone
number
Distance
(ft)
0
1
2
3
4
5
6
7
8
9
10
11
12
0
7.5
15
22.5
30
37.5
45
52.5
60
67.5
75
82.5
90
97.5
105
112.5
120
127.5
135
142.5
150
157.5
165
172.5
180
S-01A
Arrival
Time
(mS)
S-01B
Arrival
Time
(mS)
0
2.87
5.00
15.12
6.50
14.56
8.06
14.18
9.75
13.1
10.25
12.31
10.87
11.43
11.37
10.87
11.75
9.62
12.50
14.25
6.87
14.50
4.62
3
0
Accurate Velocities
Note: Survey A is shown from left to right and Survey B is shown from right to left on the graph
S-01A V1
S-01A V2
S-01B V1
S-01B V2
Change
dist
20
145
23.2
156.8
Change
time
6.1
9
8
8
Velocity
(feet/mS)
3.28
16.11
2.90
19.60
Velocity
(feet/s)
3,279
16,111
2,900
19,600
Critical
Distance
(Xc)
20.00
Depth
(feet)
8.14
23.20
9.99
114
Figure A-1 (continued)
115
Figure A-2: Seismic Survey Data for Survey S-02
Geophone
number
S-02A Arrival S-02B Arrival
Distance (ft) Time (mS) Time (mS)
0
1
2
3
4
5
6
7
8
9
10
11
12
0
7.5
15
22.5
30
37.5
45
52.5
60
67.5
75
82.5
90
97.5
105
112.5
120
127.5
135
142.5
150
157.5
165
172.5
180
Note: Survey A is shown from left to
right and Survey B is shown from right
to left on the graph
0
3.00
4.00
18.06
5.12
17.68
6.87
17.62
7.56
17.18
9.31
18.43
12.00
9.12
12.87
12.56
10.93
17.50
10.87
18.56
10.87
19.18
5.31
3.81
0
Change dist Change time
Velocity
(feet/mS)
2.17
Unreliable Data
Velocity
(feet/S)
Critical
Distance Depth
(Xc)
(feet)
2,171
7.60
S-02A V1
7.6
3.5
S-02A V2
172.4
16.5
S-02B V1
59
13.8
4.28
4,275
S-02BV2
30
3.7
8.11
8,108
10.45 10,448
3.08
38.00
10.57
116
Figure A-2 (continued)
117
Figure A-3: Seismic Survey Data for Survey S-03
Geophone
number
0
1
2
3
4
5
6
7
8
9
10
11
12
Distance
(ft)
0
7.5
15
22.5
30
37.5
45
52.5
60
67.5
75
82.5
90
97.5
105
112.5
120
127.5
135
142.5
150
157.5
165
172.5
180
S-03A
Arrival
Time (mS)
0
2.93
4.31
S-03B
Arrival
time Red
14.93
14.12
6.00
13.31
7.43
12.68
8.81
12.06
10.43
11.37
11.62
9.81
12.37
8.25
13.20
14.25
14.93
5.06
3.18
15.62
Accurate Velocities
1.81
0
Note: Survey A is shown from left to right and Survey B is shown from right to left on the graph
Change
in
distance
Change in
time
Velocity
(feet/mS)
S-03A V1
18
7.3
2.47
2,466
S-03A V2
162
9.7
16.70
16,701
S-03B V1
32
7.9
4.05
4,051
S-03B V2
148
7.8
18.97
18,974
Velocity
(feet/s)
Critical
Distance
(Xc)
Depth
(feet)
18.00
7.76
32.00
12.88
118
Figure A-3 (continued)
119
Figure A-4: Seismic Survey Data for Survey S-04
Geophone
number
S-04A
Arrival Time
(mS)
0
12.93
19.37
S-04B
Arrival
Time (mS)
24.18
32.25
26.56
33.81
26.56
32.56
26.50
30.68
27.13
28.93
105
112.5
120
127.5
28.87
28.68
29.81
27.06
135
142.5
150
157.5
165
172.5
180
31.00
Distance
(ft)
0
1
2
3
4
5
6
7
8
9
10
11
12
0
7.5
15
22.5
30
37.5
45
52.5
60
67.5
75
82.5
90
97.5
30.87
33.18
17.43
33.87
8.5
4.62
0
Accurate
Velocities
Note: Survey A is shown from left to right and Survey B is shown from right to left on the graph
Change
dist
Change time
Velocity
(feet/mS)
S-04A V1
16
24
0.67
S-04A V2
164
10
16.40
S-04B V1
24
25
0.96
S-04BV2
156
7.5
20.80
Velocity
(feet/S)
667
Distance
(Xc)
Depth
(feet)
16.00
7.68
24.00
11.46
16,400
960
20,800
120
Figure A-4 (continued)
121
Figure A-5: Seismic Survey Data for Survey S-05
Figure A-5: Seismic survey data and graph for survey S-05
S-05A
Geophone
Distance
Arrival Time S-05B Arrival
number
(ft)
(mS)
Time (mS)
0
0
0
1
7.5
2.31
2
15
4.00
20.5
22.5
3
30
6.25
19.87
37.5
4
45
7.93
18.81
52.5
5
60
9.93
17.75
67.5
6
75
11.37
16.43
82.5
7
90
13.12
14.75
97.5
8
105
14.56
12.87
112.5
9
120
16.00
10.68
127.5
10
135
19.93
142.5
11
150
21.00
8.31
157.5
12
165
22.18
6.06
172.5
4.68
180
0
Accurate Velocities
Note: Survey A is shown from left to right and Survey B is shown from right to left on the graph
Change in
distance
Change in
time
Velocity
(feet/mS)
Velocity
(feet/S)
S-05A V1
8
5
1.60
1,600
S-05A V2
172
18
9.56
9,556
S-05B V1
9
6
1.50
1,500
S-05B V2
171
18
9.50
9,500
Critical
Distance
(Xc)
Depth
(feet)
8.00
3.38
9.00
3.84
122
Figure A-5 (continued)
123
Figure A-6: Seismic Survey Data for Survey S-06
Geophone
number
Distance
(ft)
0
1
2
3
4
5
6
7
8
9
10
11
12
0
7.5
15
22.5
30
37.5
45
52.5
60
67.5
75
82.5
90
97.5
105
112.5
120
127.5
135
142.5
150
157.5
165
172.5
180
S-06A
Arrival
(mS)
S-06B
Arrival
(mS)
0
1.68
3.75
21.06
5.75
20.56
9.43
20
10.06
18.31
10.93
15.12
13.81
14.81
14.93
14.43
15.31
12.5
18.56
21.06
9.12
22.37
7.87
5.37
0
Unreliable
Data
Note: Survey A is shown from left to right and Survey B is shown from right to left on the graph
Change
dist
Change
time
Velocity
(feet/mS)
Velocity
(feet/S)
S-06A V1
36.5
10
3.65
3,650
S-06A V2
143.5
8.7
16.49
16,494
S-06B V1
14
11.6
1.21
1,207
S-06B V2
166
8.4
19.76
19,762
Critical
Distance
(Xc)
Depth (feet)
36.5
14.57
14.0
6.58
124
Figure A-6 (continued)
125
Figure A-7: Seismic Survey Data for Survey S-07
Geophone
number
S-07A
Arrival
Time (mS)
Distance
(ft)
0
1
2
3
4
5
6
7
8
9
10
11
12
0
7.5
15
22.5
30
37.5
45
52.5
60
67.5
75
82.5
90
97.5
105
112.5
120
127.5
135
142.5
150
157.5
165
172.5
180
S-07B
Arrival
Time (mS)
0
4.68
7.87
19.87
10.56
18.56
12.43
18.87
13.31
19.12
14.00
18.56
14.32
17.43
15.50
15.93
16.93
15.81
17.87
15.25
17.93
13.87
18.81
9.68
5.75
0
Accurate Velocities
Note: Survey A is shown from left to right and Survey B is shown from right to left on the graph
Change
distance
S-07A V1
S-07A V2
S-07B V1
S-07B V2
Change
time (mS)
Velocity
(feet/mS)
Velocity
(feet/S)
21
11
1.91
1,909
159
9
17.67
17,667
16
13.8
1.16
1,159
164
9.5
17.26
17,263
Critical
Distance
(Xc)
Depth
(feet)
21.00
9.42
16.00
7.48
126
Figure A-7 (continued)
127
Figure A-8: Seismic Survey Data for Survey S-08
Geophone
number
Distance
(ft)
S-08A Arrival
Time (mS)
0
4.93
8.18
0
1
2
S-08B Arrival
Time (mS)
0
6
15
29.18
22.5
3
30
28.81
37.5
4
45
21.56
28
52.5
5
60
21.62
26.37
67.5
6
75
21.81
26.06
82.5
7
90
22.81
25.43
97.5
8
105
25.62
25.62
112.5
9
120
26.87
20.25
127.5
10
135
27.43
142.5
11
150
28.28
17.06
157.5
12
165
29.15
8 Accurate Velocities
172.5
4.68
180
0
Note: Survey A is shown from left to right and Survey B is shown from right to left on the graph
Change in
distance
Change in
time
Velocity
(feet/mS)
Velocity
(feet/S)
S-08A V1
30
20
1.50
1,500.00
S-08A V2
150
8.5
17.65
17,647.06
S-08B V1
37
22
1.68
1,681.82
S-08B V2
143
8
17.88
17,875.00
Critical
Distance
(Xc)
Depth
(feet)
30.00
13.77
37.00
16.83
128
Figure A-8 (continued)
129
Figure A-9: Seismic Survey Data for Survey S-09
Geophone
number
Distance
(ft)
S-09A Arrival
Time (mS)
0
4.12
6.37
0
1
2
S-09B Arrival
Time (mS)
0
6
15
15.68
22.5
3
30
15.87
37.5
4
45
9.31
15.68
52.5
5
60
10.62
14.87
67.5
6
75
12.81
14.62
82.5
7
90
13.87
14.62
97.5
8
105
14.31
12.25
112.5
9
120
14.93
10
127.5
10
135
15.37
8.87
142.5
11
150
15.43
7.06
157.5
12
165
15.68
5.25
172.5
2.31 Accurate Velocities
180
0
Note: Survey A is shown from left to right and Survey B is shown from right to left on the graph
Change
distance
Change time
Velocity
(feet/mS)
Velocity
(feet/S)
S-09A V1
15
10
1.50
1,500
S-09A V2
165
8
20.63
20,625
S-09B V1
20
9
2.22
2,222
S-09B V2
160
8
20.00
20,000
Distance
(Xc)
Depth
(feet)
15.00
6.97
20.00
8.94
130
Figure A-9 (continued)
131
APPENDIX B
Soil Boring Logs
132
Figure B-1: Soil Boring SB-01
PROJECT :
ELEVATION :
METHOD :
WATER
LEVELS :
USCS
2.6
DEPTH BELOW SURFACE
(FT)
LOCATION
Thesis
~6550
Hand
Auger
BORING NUMBER: SB-01
Van Vleck Meadow, El
Dorado County, CA
TD
4.8 ft
LOGGER
Mancuso
DATE: 10/24/2009
SOIL DESCRIPTION
SIZE
DISTRIBUTION
%G
%S
%F
ML
0
30
70
SP
0
90
10
Sandy silt (ML), dark brown, wet to saturated, mostly root mass top 0.9
ft, had slight biodecay/organic odor
_
_
_
Sand (SP), dark grayish brown, wet, sand is medium to fine,
occasional gravel (coarse and subangular to sub round)
_
0
5 __
_
_
_
_
10 __
Refusal
133
Figure B-2: Soil Boring SB-02
LOCATION
Thesis
~6500 ft
Hand
METHOD:
Auger
WATER LEVEL: 3.2 ft
bgs
DATE: 10/24/2009
USCS
DEPTH BELOW SURFACE
(FT)
PROJECT :
ELEVATION :
NA
TD: 3.85 ft
LOGGER :
%S
%F
ML
0
30
70
SP
0
90
10
L. Mancuso
SOIL DESCRIPTION
SIZE
DISTRIBUTION
%G
SBBORING
02
NUMBER
Van Vleck Meadow, El Dorado
County, CA
Sandy silt (ML), dark brown, wet to saturated, some root mass top 1
ft, had slight biodecay/organic odor
_
_
_
Sand (SP), dark grayish brown, wet, sand is medium to fine,
occasional gravel (coarse and subangular to sub round)
_
0
5 __
_
_
_
_
10 __
_
Refusal
134
Figure B-3: Soil Boring SB-03
BORING
NUMBER
PROJECT :
ELEVATION :
METHOD:
USCS
DEPTH BELOW SURFACE
(FT)
LOCATION
Thesis
~6500
Hand Auger
WATER LEVEL: 2.5 ft bgs
SB-03
Van Vleck Meadow, El Dorado
County, CA
TD: 3.98 ft
DATE: 10/24/2009
SOIL DESCRIPTION
SIZE
DISTRIBUTION
%G
%S
%F
ML
0
30
70
SP
0
90
10
LOGGER: L.Mancuso
Sandy silt (ML), dark brown, wet to saturated, some root mass top
0.5 ft, very slight organic/biodecay odor
_
_
_
Sand (SP), dark grayish brown, wet, sand is medium to fine,
occasional gravel (coarse and subangular to subround)
_
3.98 ft bgs
5 __
_
_
_
_
10 __
_
Refusal
135
Figure B-4: Soil Boring SB-04
SB04
BORING
NUMBER
USCS
DEPTH BELOW SURFACE
(FT)
Thesis
~6500
Hand
METHOD:
Auger
WATER LEVEL: 1.1 ft
bgs
LOCATION
PROJECT :
ELEVATION :
ML
Van Vleck Meadow, El Dorado
County, CA
TD: 3.43 ft bgs
DATE: 10/24/2009
%S
%F
0
30
70
L. Mancuso
SOIL DESCRIPTION
SIZE
DISTRIBUTION
%G
LOGGER :
Sandy silt (ML), dark brown, wet , some root mass top 0.4 ft
_
Saturated
_
_
SP
0
90
10
Sand (SP), dark grayish brown, wet, sand is medium to fine,
occasional gravel (coarse and subangular to subround)
_
Refusal at 3.43 ft
5 __
_
_
_
_
10 __
_
136
Figure B-5: Soil Boring SB-05
BORING
NUMBER
LOCATION
PROJECT :
ELEVATION :
USCS
DEPTH BELOW SURFACE
(FT)
Thesis
~6500
Hand
METHOD:
Auger
WATER LEVEL: 2.3 ft
bgs
ML
SB-05
Van Vleck Meadow, El Dorado
County, CA
TD: 6 ft bgs
DATE: 10/24/2009
%S
%F
0
30
70
L. Mancuso
SOIL DESCRIPTION
SIZE
DISTRIBUTION
%G
LOGGER
Sandy silt (ML), dark brown, wet to saturated, some root mass and
sticks top 0.5 ft,
_
_
_
_
Encountered some gravel, coarse subround
SP
0
90
10
Sand (SP), dark grayish brown, saturated, sand is medium to fine,
occasional gravel (coarse and subangular to subround)
5 __
_
_
_
_
10 __
_
6 ft bgs
Refusal - Unable to hand auger past 6 ft because
vacuum on auger is too great when pulled up
137
Figure B-6: Soil Boring SB-06
BORING
NUMBER
Thesis
~6500 ft
Hand
METHOD:
Auger
WATER LEVEL: 1.1 ft
bgs
DATE: 10/24/2009
USCS
DEPTH BELOW SURFACE
(FT)
PROJECT :
ELEVATION :
SB-06
LOCATION
%S
%F
ML
0
30
70
SP
0
90
10
TD:
LOGGER :
3.31
ft
L. Mancuso
SOIL DESCRIPTION
SIZE
DISTRIBUTION
%G
Van Vleck Meadow, El Dorado
County, CA
Sandy silt (ML), dark brown, wet to saturated, some root mass top
0.4 ft
_
_
_
Sand (SP), dark grayish brown, wet, sand is medium to fine,
occasional gravel (coarse and subangular to subround)
_
Refusal at 3.31 ft
5 __
_
_
_
_
10 __
_
138
Figure B-7: Soil Boring SB-07
BORING
NUMBER
Thesis
~6500 ft
Hand
METHOD:
Auger
WATER LEVEL: 2.6 ft
bgs
DATE: 10/24/2009
USCS
DEPTH BELOW SURFACE
(FT)
PROJECT :
ELEVATION :
SB-07
LOCATION
%S
%F
ML
0
30
70
SP
0
90
10
TD:
LOGGER :
4.67
L.
Mancuso
SOIL DESCRIPTION
SIZE
DISTRIBUTION
%G
Van Vleck Meadow, El Dorado
County, CA
Sandy silt (ML), dark brown, wet to saturated, some root mass top 1
ft
_
_
_
Sand (SP), dark grayish brown, wet, sand is medium to fine,
occasional gravel (coarse and subangular to subround)
_
Refusal at 4.67 ft
5 __
_
_
_
_
10 __
_
139
Figure B-8: Soil Boring SB-08
BORING NUMBER
DEPTH BELOW SURFACE
(FT)
PROJECT :
Thesis
ELEVATION :
~6500 ft
DRILLING METHOD AND EQUIPMENT
USED :
DATE:
WATER LEVEL: 0.9 ft bgs
10/24/2009
SB-08
LOCATION :
Van Vleck Meadow, El
Dorado County, CA
Hand Auger
TD:
LOGGER :
3.00
L.
Mancuso
USCS
SOIL DESCRIPTION
SIZE DISTRIBUTION
%G
%S
%F
ML
0
30
70
Sandy silt (ML), dark brown, wet to saturated, some root
mass top 1 ft
SP
0
90
10
Sand (SP), dark grayish brown, wet, sand is medium to
fine, occasional gravel (coarse and subangular to
subround)
_
_
_
_
Refusal at 3.0 ft
5 __
_
_
_
_
10 __
_
140
Figure B-9: Soil Boring SB-09
BORING
NUMBER
PROJECT :
ELEVATION :
LOCATION
Thesis
~6500 ft
Hand
Auger
METHOD:
WATER
LEVELS :
USCS
DEPTH BELOW SURFACE
(FT)
0.6
SB-09
Van Vleck Meadow, El
Dorado County, CA
TD:
DATE: 10/25/2009
SIZE
DISTRIBUTION
%G
%S
%F
ML
0
30
70
SP
0
90
10
LOGGER :
2.25
Mancuso
SOIL DESCRIPTION
Sandy silt (ML), dark brown, wet to saturated, some root mass
top 0.4 ft
_
_
_
Sand (SP), dark grayish brown, wet, sand is medium to fine,
occasional gravel (coarse and subangular to subround)
_
5 __
_
_
_
_
10 __
Refusal at 2.25 ft
refusal surface felt smooth and flat (large
boulder)
141
Figure B-10: Soil Boring SB-10
BORING
NUMBER
Thesis
~6500 ft
Hand
METHOD:
Auger
WATER LEVEL: 0.7 ft
bgs
DATE: 10/25/2009
USCS
DEPTH BELOW SURFACE
(FT)
PROJECT :
ELEVATION :
SB-10
LOCATION
Van Vleck Meadow, El Dorado
County, CA
TD:
2.38
LOGGER
SOIL DESCRIPTION
SIZE
DISTRIBUTION
%G
%S
%F
ML
0
30
70
SP
0
90
10
L. Mancuso
Sandy silt (ML), dark brown, wet to saturated, some root mass top
0.4 ft
_
_
_
Sand (SP), dark grayish brown, wet, sand is medium to fine,
occasional gravel (coarse and subangular to subround)
_
Refusal at 2.38 ft
5 __
_
_
_
_
10 __
_
refusal surface felt smooth and flat (large boulder)
142
Figure B-11: Soil Boring SB-11
BORING
PROJECT :
ELEVATION :
Thesis
~6500 ft
Hand
Auger
1.3
DATE: 10/25/2009
SIZE
DISTRIBUTION
USCS
DEPTH BELOW SURFACE
(FT)
METHOD:
WATER LEVEL:
1.3
SB11
LOC.
Van Vleck Meadow, El
Dorado County, CA
TD
4.56
LOGGER
L. Mancuso
SOIL DESCRIPTION
%G
%S
%F
ML
0
30
70
Sandy silt (ML), dark brown, wet to saturated, some root
mass top 0.4 ft
SP
0
90
10
Sand (SP), dark grayish brown, wet, sand is medium to
fine, occasional gravel (coarse and subangular to
subround)
_
_
_
_
5 __
_
_
_
_
10 __
Refusal at 4.56 ft
refusal surface felt smooth and flat (large
boulder)
143
Figure B-12: Soil Boring SB-12
BORING
NUMBER
Thesis
~6500 ft
Hand
METHOD:
Auger
WATER LEVEL: 0.3 ft
bgs
DATE: 10/25/2009
USCS
DEPTH BELOW SURFACE
(FT)
PROJECT :
ELEVATION :
SB-12
LOCATION
Van Vleck Meadow, El Dorado
County, CA
TD:
2.75
LOGGER
SOIL DESCRIPTION
SIZE
DISTRIBUTION
%G
%S
%F
ML
0
30
70
SP
0
90
10
L. Mancuso
Sandy silt (ML), dark brown, wet to saturated, some root mass top 0.5 ft
_
_
_
Sand (SP), dark grayish brown, wet, sand is medium to fine, occasional
gravel (coarse and subangular to sub round)
_
Refusal at 2.75ft
5 __
_
_
_
_
10 __
_
144
Figure B-13: Soil Boring SB-13
BORING NUMBER
PROJECT :
ELEVATION
:
LOCATION :
Thesis
USCS
DEPTH BELOW SURFACE
(FT)
~6500 ft
Hand
METHOD:
Auger
WATER LEVEL: 1
DATE:
ft
10/25/2009
%G
%S
%F
0
30
70
SP
0
90
10
Van Vleck Meadow, El Dorado
County, CA
TD:
LOGGER :
4.2
L. Mancuso
SOIL DESCRIPTION
SIZE
DISTRIBUTION
ML
SB-13
Sandy silt (ML), dark brown, wet to saturated, some root mass top 0.5 ft
_
_
_
Sand (SP), dark grayish brown, wet, sand is medium to fine, occasional
gravel (coarse and subangular to sub round)
_
Refusal at 4.2 ft
5 __
_
_
_
_
10 __
145
Figure B-14: Soil Boring SB-14
BORING
NUMBER
PROJECT :
ELEVATION
:
Thesis
USCS
DEPTH BELOW SURFACE
(FT)
METHOD:
WATER LEVEL:
1.8
~6500 ft
Hand
Auger
SB-14
LOCATION
Van Vleck Meadow, El Dorado County,
CA
TD:
2.7
DATE: 10/25/2009
%S
%F
ML
0
20
80
SP
0
90
10
L. Mancuso
SOIL DESCRIPTION
SIZE
DISTRIBUTION
%G
LOGGER
Silt with sand (ML), dark brown, wet to saturated, mostly root mass top 0.8 ft,
slight organic/biodecay odor
_
_
_
Sand (SP), dark grayish brown, wet, sand is medium to fine, occasional gravel
(coarse and subangular to sub round)
Refusal at 2.7 ft
_
5 __
_
_
_
_
10 __
146
Figure B-15: Soil Boring SB-15
BORING
NUMBER
PROJECT :
ELEVATION
:
Thesis
USCS
DEPTH BELOW SURFACE
(FT)
METHOD:
WATER LEVEL:
2.2 ft
~6500 ft
Hand
Auger
SB-15
LOCATION
Van Vleck Meadow, El Dorado County,
CA
TD:
2.9
DATE: 10/25/2009
%S
%F
ML
0
20
80
SP
0
90
10
L. Mancuso
SOIL DESCRIPTION
SIZE
DISTRIBUTION
%G
LOGGER
Silt with sand (ML), dark brown, wet to saturated, mostly root mass top 0.8 ft,
slight organic/biodecay odor
_
_
_
Sand (SP), dark grayish brown, wet, sand is medium to fine, occasional
gravel (coarse and subangular to sub round)
Refusal at 2.9 ft
_
5 __
_
_
_
_
10 __
147
Figure B-16: Soil Boring SB-16
BORING
NUMBER
PROJECT :
ELEVATION
:
USCS
DEPTH BELOW SURFACE
(FT)
LOCATION
Thesis
METHOD:
WATER LEVEL:
0.5
SB-16
~6500 ft
Hand
Auger
Van Vleck Meadow, El Dorado
County, CA
TD:
DATE: 10/10/2010
SOIL DESCRIPTION
SIZE
DISTRIBUTION
%G
%S
%F
ML
0
20
80
SP
0
90
10
LOGGER :
3.5
L.
Mancuso
Silt with sand (ML), dark brown, wet to saturated, mostly root mass
top 0.8 ft, slight organic/biodecay odor
_
_
_
Sand (SP), dark grayish brown, wet, sand is medium to fine,
occasional gravel (coarse and subangular to sub round)
Refusal at 3.5 ft
_
5 __
_
_
_
_
10 __
148
Figure B-17: Soil Boring SB-17
BORING NUMBER
PROJECT :
ELEVATION
:
METHOD:
WATER LEVEL:
0.9 ft
USCS
DEPTH BELOW SURFACE
(FT)
LOCATION :
Thesis
~6500 ft
Hand
Auger
SB-17
Van Vleck Meadow, El Dorado
County, CA
TD:
DATE:
10/10/2010
LOGGER :
%G
%S
%F
0
20
80
SP
0
90
10
L. Mancuso
SOIL DESCRIPTION
SIZE
DISTRIBUTION
ML
3.75
Silt with sand (ML), dark brown, wet to saturated, mostly root mass
top 0.5 ft, slight organic/biodecay odor
_
_
_
Sand (SP), dark grayish brown, wet, sand is medium to fine,
occasional gravel (coarse and subangular to sub round)
Refusal at 3.75 ft
_
5 __
_
_
_
_
10 __
149
Figure B-18: Soil Boring SB-18
PROJECT :
ELEVATION :
Thesis
~6500 ft
Hand
Auger
METHOD:
WATER
LEVELS :
DATE:
10/10/2010
USCS
DEPTH BELOW SURFACE
(FT)
0.5 ft bgs
BORING NUMBER
SB-18
LOCATION :
Van Vleck Meadow, El
Dorado County, CA
TD:
3.25
LOGGER :
SOIL DESCRIPTION
SIZE
DISTRIBUTION
%G
%S
%F
ML
0
20
80
SP
0
90
10
L. Mancuso
Silt with sand (ML), dark brown, wet to saturated, mostly root
mass top 0.8 ft, slight organic/biodecay odor
_
_
_
Sand (SP), dark grayish brown, wet, sand is medium to fine,
occasional gravel (coarse and subangular to sub round)
Refusal at 3.5 ft
_
5 __
_
_
_
_
150
Figure B-19: Soil Boring SB-19
BORING NUMBER
PROJECT :
ELEVATION :
Thesis
~6500 ft
Hand
Auger
METHOD:
WATER LEVEL:
1.8 ft
USCS
DEPTH BELOW SURFACE
(FT)
1.8 ft bgs
DATE:
10/10/2010
SB-19
LOCATION :
Van Vleck Meadow, El
Dorado County, CA
TD:
3
LOGGER :
L. Mancuso
SOIL DESCRIPTION
SIZE
DISTRIBUTION
%G
%S
%F
ML
0
20
80
Silt with sand (ML), dark brown, wet, mostly root mass top
0.5 ft, slight organic/biodecay odor
SP
0
90
10
2.5 became saturated
Sand (SP), dark grayish brown, wet, sand is medium to
fine, occasional gravel (coarse and subangular to sub
round)
_
_
_
Refusal at 3.0 ft
_
5 __
_
_
_
_
151
Figure B-20: Soil Boring SB-20
BORING
NUMBER
SB-20
LOCATION
:
%G
%S
%F
ML
0
20
80
SP
0
90
10
TD:
LOGGER :
3
L.
Mancuso
SOIL DESCRIPTION
SIZE
DISTRIBUTION
USCS
DEPTH BELOW SURFACE
(FT)
PROJECT :
Thesis
ELEVATION :
METHOD:
Hand Auger
WATER
LEVELS :
1 ft bgs
DATE: 10/15/2010
Van Vleck Meadow,
El Dorado County,
CA
Silt with sand (ML), dark brown, wet to saturated, mostly root
mass top 0.5 ft, slight organic/biodecay odor
_
_
_
Sand (SP), dark grayish brown, wet, sand is medium to fine,
occasional gravel (coarse and subangular to sub round)
Refusal at 3.0 ft
_
5 __
_
_
_
_
10 __
152
Figure B-21: Soil Boring SB-21
SB21
BORING NUMBER
PROJECT :
ELEVATION :
METHOD:
WATER
LEVELS :
USCS
1.8 ft bgs
DEPTH BELOW SURFACE
(FT)
LOCATION
Thesis
~6500 ft
Hand
Auger
Van Vleck Meadow, El
Dorado County, CA
TD:
DATE: 10/15/2010
SOIL DESCRIPTION
SIZE
DISTRIBUTION
%G
%S
%F
ML
0
20
80
SP
0
90
10
LOGGER :
2.5
L.
Mancuso
Silt with sand (ML), dark brown, wet to saturated, mostly root mass
top 0.5 ft, slight organic/biodecay odor
_
_
_
Sand (SP), dark grayish brown, wet, sand is medium to fine,
occasional gravel (coarse and subangular to sub round)
Refusal at 2.5 ft
_
5 __
_
_
_
_
10 __
_
153
APPENDIX C
Piezometer Construction Details
154
Table C-1: Piezometer Construction Details
Date Installed
Total Depth
(ft bgs)
Transducer depth
(ft bgs)
PZ-01
10/24/2009
4.8
2.8
PZ-02
10/24/2009
3.85
2.85
PZ-03
10/24/2009
3.98
2.98
PZ-04
10/24/2009
3.43
2.43
PZ-05
10/24/2009
4.84
3.84
PZ-06
10/24/2009
3.31
2.31
PZ-07
10/24/2009
4.67
3.67
PZ-08
10/24/2009
3
2
PZ-09
11/8/2009
2.33
2.25
PZ-10
11/8/2009
2.46
2.38
PZ-11
11/8/2009
5.36
4.56
PZ-12
11/8/2009
2.83
2.75
PZ-13
11/8/2009
4.27
4.19
PZ-14
11/8/2009
2.79
2.71
PZ-15
11/8/2009
2.96
2.88
Riser Material
Screen Material
Solinst
screen
attachment
Schedule 40
PVC, 1-inch
diameter
PVC with slots
and wrapped in
landscape mesh
155
APPENDIX D
Lab Reports and Standard Operating Procedures
156
Figure D-1: Grain size summary
156
157
158
159
Figure D-2: Effective porosity results
160
Figure D-3: Grain size analysis SOP
161
162
Figure D-4: Effective porosity SOP
163
164
APPENDIX E
Groundwater Level and Temperature Graphs
165
Figure E-1: Water levels and average temperature at piezometer PZ-01
165
166
Figure E-2: Water levels and average temperature at piezometer PZ-03
166
167
Figure E-3: Water levels and average temperature at piezometer PZ-04
167
168
Figure E-4: Water levels and average temperature at piezometer PZ-05
168
169
Figure E-5: Water levels and average temperature at piezometer PZ-06
169
170
Figure E-6: Water levels and average temperature at piezometer PZ-07
170
171
Figure E-7: Water levels and average temperature at piezometer PZ-08
171
172
Figure E-8: Water levels and average temperature at piezometer PZ-10
172
173
Figure E-9: Water levels and average temperature at piezometer PZ-11
173
174
Figure E-10: Water levels and average temperature at piezometer PZ-12
174
175
Figure E-11: Water levels and average temperature at piezometer PZ-13
175
176
APPENDIX F
Overflow Channel Discharge Calculations
177
Table F-1: Overflow channel calculations- water level 2.4 ft
Variable
Q
Description
Formula
3
Solve
2/3
1/2
Result
0.4
discharge, m /s
(1.0/n)A(R )(S )
0.433
discharge, af/day
Q*70.0456199
30.353
A
cross-sectional area of channel
(y/2)(b +T)
0.966
30.4
0.966
S
bottom slope of channel
(s1 – x3)/d
0.004
0.004
n
Manning roughness coefficient,
coarse gravel with cobbles (Cowan,
1956)
R
hydraulic radius
A/P
0.115
P
wetted perimeter cross-sectional flow
area
a+b+c
8.42
y
height overflow area
Units
m3/s
af/day
m2
0.035
0.115
m
8.4
((y1+y2)/2)
((y3+y4/2))
-
0.21
m
m
0.21
b
base overflow area
x3-x4
0.8
0.8
m
T
top overflow area
x2-x1
8.4
8.4
m
a
left bank length
sqrt(y2 + (x1-x4)2)
1.61
1.61
6.00
6.00
2
2
m
m
c
right bank length
sqrt(y + (x2-x3) )
x1
x value - top left
from survey/graph
-4.1
m
y1
y value - top left
from survey/graph
99.79
m
x2
x value - top right
from survey/graph
4.3
m
y2
y value - top right
from survey /graph
99.79
m
x3
x value - bottom right
from survey/graph
-1.7
m
y3
y value - bottom right
from survey/graph
99.6
m
x4
x value - bottom left
from survey graph
-2.5
m
y4
y value - bottom left
from survey/graph
99.56
m
s1
overflow channel elevation
from survey/graph
99.68
m
d
distance - overflow channel to road
from
points
(2.7,9.8) to (-2.5, 7.5)
18.1
m
178
Table F-2: Overflow channel calculations- water level of 2.2 ft
Variable
Q
Description
discharge, m3/s
Formula
Solve
2/3
1/2
(1.0/n)A(R )(S )
0.307
Result
0.3067
discharge, af/day
Q*70.0456199
A
cross-sectional area of channel
(y/2)(b +T)
0.864
21.5
0.864
S
bottom slope of channel
(s1 – x3)/d
0.003
0.003
n
Manning roughness coefficient, for
coarse gravel with cobbles (Cowan,
1956)
hydraulic radius
R
P
A/P
y
b
base of the overflow area
x3-x4
T
top of the overflow area
x2-x1
a
left bank length
c
right bank length
x1
x value for top left side of trapezoid
y1
y value for top left side of trapezoid
x2
x value for top right side of trapezoid
y2
y value for top right side of trapezoid
x3
x value for bottom right
trapezoid
y value for bottom right
trapezoid
x value for bottom left
trapezoid
y value for bottom left
trapezoid
overflow channel elevation
y3
x4
y4
s1
d
side of
side of
side of
distance from overflow channel to
road
m3/s
af/day
m2
0.035
wetted perimeter of cross-sectional
flow area
height of the overflow area
side of
21.480
Units
0.115
0.115
m
7.5
a+b+c
((y1+y2)/2) ((y3+y4/2))
7.52
0.135
m
m
5.3
5.3
m
7.5
7.5
m
sqrt(y2 + (x1-x4)2)
1.51
1.51
sqrt(y2 + (x2-x3)2)
from survey
points/graph
from survey
points/graph
from survey
points/graph
from survey
points/graph
from survey
points/graph
from survey
points/graph
from survey
points/graph
from survey
points/graph
from survey
points/graph
from points
(2.7,9.8) to (-2.5, 7.5)
0.71
0.71
0.135
m
m
-4
m
99.73
m
3.5
m
99.73
m
2.8
m
99.63
m
-2.5
m
99.56
m
99.68
m
18.1
m
179
Table F-3: Overflow channel calculations- water level of 2.0 ft
Variable
Q
A
S
n
R
P
Description
discharge, m3/s
Formula
discharge, af/day
Q*70.0456199
cross-sectional area of
channel
bottom slope of channel
(y/2)(b +T)
0.554
(s1 – x3)/d
0.004
Manning
roughness
coefficient,
for
coarse
gravel
with
cobbles
(Cowan, 1956)
hydraulic radius
A/P
y
b
base of the overflow area
x3-x4
T
top of the overflow area
x2-x1
a
left bank length
c
right bank length
x1
x value for top left side of
trapezoid
y value for top left side of
trapezoid
x value for top right side of
trapezoid
y value for top right side of
trapezoid
x value for bottom right
side of trapezoid
y value for bottom right
side of trapezoid
x value for bottom left side
of trapezoid
y value for bottom left side
of trapezoid
overflow channel elevation
y2
x3
y3
x4
y4
s1
d
distance from
channel to road
overflow
0.193
13.550
Result
0.1934
13.6
0.554
Units
m3/s
af/day
m2
0.004
0.035
a+b+c
x2
1/2
(1.0/n)A(R )(S )
wetted perimeter of crosssectional flow area
height of the overflow area
y1
Solve
2/3
0.079
0.079
m
7.0
0.09
0.09
m
m
5.3
5.3
m
7
7
m
sqrt(y2 + (x1-x4)2)
1.30
1.30
m
sqrt(y2 + (x2-x3)2)
0.41
0.41
((y1+y2)/2) - ((y3+y4/2))
7.01
m
from survey points/graph
-3.8
m
from survey points/graph
99.67
m
from survey points/graph
3.2
m
from survey points/graph
99.67
m
from survey points/graph
2.8
m
from survey points/graph
99.6
m
from survey points/graph
-2.5
m
from survey points/graph
99.56
m
from survey points/graph
from points (2.7,9.8) to (2.5, -7.5)
99.68
m
18.1
m
180
Table F-4: Overflow channel calculations- water level of 1.82 ft
Variable
Q
Description
discharge, m3/s
Formula
Solve
(1.0/n)A(R )(S )
0.007
2/3
1/2
Result
0.0069
discharge, af/day
Q*70.0456199
0.482
A
cross-sectional area of channel
(y/2)(b +T)
0.050
0.5
0.050
S
bottom slope of channel
(s1 – x3)/d
0.004
0.004
n
Manning roughness coefficient,
for coarse gravel with cobbles
(Cowan, 1956)
hydraulic radius
R
P
A/P
y
b
base of the overflow area
x3-x4
T
top of the overflow area
x2-x1
a
left bank length
c
right bank length
x1
x value for top left side
trapezoid
y value for top left side
trapezoid
x value for top right side
trapezoid
y value for top right side
trapezoid
x value for bottom right side
trapezoid
y value for bottom right side
trapezoid
x value for bottom left side
trapezoid
y value for bottom left side
trapezoid
overflow channel elevation
x2
y2
x3
y3
x4
y4
s1
d
m3/s
af/day
m2
0.035
wetted perimeter of crosssectional flow area
height of the overflow area
y1
Units
0.020
0.020
m
2.5
a+b+c
((y1+y2)/2) ((y3+y4/2))
2.50
0.03
m
m
0.8
0.8
m
2.5
2.5
m
sqrt(y2 + (x1-x4)2)
1.00
1.00
sqrt(y2 + (x2-x3)2)
0.70
0.70
0.03
m
m
of
from survey points/graph
-3.5
m
from survey points/graph
99.61
m
from survey points/graph
-1
m
from survey points/graph
99.61
m
from survey points/graph
-1.7
m
from survey points/graph
99.6
m
from survey points/graph
-2.5
m
from survey points/graph
99.56
m
from survey points/graph
from points (2.7,9.8) to
(-2.5, -7.5)
99.68
m
18.1
m
of
of
of
of
of
of
of
distance from overflow channel
to road
181
Figure F-1: Outflow area plan view
182
Figure F-2: Outflow area profile view
183
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