Description of Project
Background
Kansas streams and their associated riparian corridors are one of the state’s most vital
natural resources. Perennial streams provide a large percentage of the state’s
population with water for drinking, irrigation, and recreation. Kansas stream corridors
are undergoing adjustments and degradation due to land use changes from agriculture
and urban development. The cumulative effect of these changes is an increase in
chemical and sediment pollution, a decrease in aquatic and terrestrial wildlife habitat,
and an increase in property loss due to flooding and erosion.
A stream is a product of its watershed. The watershed’s climate, topography, geology,
vegetative cover, and landuse all combine to determine the physical characteristics of a
stream. Stream channel dimension, pattern, and profile along with riparian condition and
sediment loads and sources, are measurements used to describe the physical
characteristics of a watershed. This type of data was previously unavailable.
In 1998, the Kansas Water Office was awarded an United States Environmental
Protection Agency grant for the: Geomorphic Assessment and Classification of Kansas
Riparian Systems. The purpose of the grant is to collect baseline stream corridor data.
This information will enhance our understanding on the function of Kansas stream
corridors. The collected data will allow State agency personnel, and others, to begin
applying a watershed approach to stream corridor protection and restoration. The
current approach is a site specific, or patch in place method for addressing impaired
stream corridors.
Project Objectives
The primary objective of this project is to gather fluvial geomorphology and ancillary
data necessary for understanding stream function and proper stream corridor
management.
Additional objectives include:
1. Apply a uniform stream classification system to Kansas watersheds.
2. Design and implement streambank stabilization and riparian restoration
demonstration projects on selected stream reaches.
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Project Approach
The predominate factor affecting the physical characteristics of stream corridors is
bankfull flow. Bankfull flow is the peak of effective discharge and determines the
physical characteristics and dimensions of a stream channel. It is the dominant channelforming flow. This volume of flow varies from stream to stream, but the frequency of
occurrence for most streams is similar. In Kansas, bankfull flow has a recurrence
interval between 1.1 and 1.6 years depending on the stream’s drainage area and
location in the state. The recurrence range reflects the flood frequency over time;
meaning that the bankfull flow may not occur at this frequency from year to year, but
rather it is likely to occur. Large flow events are too infrequent to govern channel
characteristics, though high flow events are effective at channel change when they do
occur (Dunne and Leopold, 1978). Low flow conditions are common and frequent and
ineffective at shaping the channel (Dunne and Leopold, 1978). There are several
bankfull flow indicators in Kansas. These include: the presence of an active floodplain at
the incipient point of flooding, an elevation associated with the top of the highest
depositional features, a break in bank slope, a change in particle size distribution,
presence of small benches, and exposed roots below an intact soil layer. These
indicators are not consistent from site to site nor are they always readily visible.
To document the correct elevation of the bankfull flow, data is collected at or near
United States Geological Survey (USGS) stream-flow gaging stations. USGS maintains
approximately 140 stream-flow gaging stations in Kansas. Streamflow data collected at
each site includes: width, area, mean velocity, water elevation, and discharge. The
drainage area is also documented for each gage station. This data is collected on a
frequent basis for a water resource information database. Over time, this information is
recorded for a wide variety of flow conditions, and is documented in discharge notes (9207 forms). USGS also develops rating tables for each gage. These tables list the
discharge at a particular elevation. Further data analysis of the USGS measurements
provide information for two aspects of the stream flow: 1) flood recurrence interval, in
years, from flood frequency analysis and 2) hydraulic geometry data for channel width,
depth, cross sectional area, and flow velocity vs. stream discharge. Regression analysis
is performed on the latter to obtain relationships between discharge and the width,
depth, cross sectional area, and velocity of a particular flow. In many cases these
relationships are very accurate.
Collecting data at USGS gage locations is necessary to verify a field determined
bankfull stage. At the present time, surveying is complete at 86 gaging stations. Some
stations are excluded due to controlled flow conditions immediately upstream of the
gaging station (reservoirs).
Data Collection Procedures
In order to document the physical characteristics of stream corridors, surveys are
conducted to determine the dimension, pattern, profile, riparian condition, and sediment
yield (at a given discharge) for each suitable USGS gage station.
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Dimension
Each site survey has at least one cross section. Several surveys have cross
sections for riffles and pools; and others for reference and degraded stream
reaches. Rebar pins are placed at each end of the cross section to allow
additional surveys to measure the same cross section and document any
changes. Each cross section normally starts at the top of left bank and ends at
top of right bank. The cross section used to determine dimension data is located
on a riffle or cross over section of the stream reach. These locations in a stream
tend to have the highest stability. The following information is gathered from each
cross section survey:
1. Bankfull Width
2. Bankfull Mean Depth
3. Bankfull Cross Sectional Area
4. Width / Depth Ratio
5. Maximum Depth
6. Width of Flood Prone Area
7. Entrenchment Ratio
8. Wetted Perimeter
9. Mean Velocity @ Bankfull Stage
10. Bankfull Discharge Estimate
11. Ratio: Lowest Bank Height / Bankfull Maximum Depth
Pattern
Channel pattern data is collected for each site to document the configuration
of the channel as it meanders through the valley. Most of this data is gathered
in the office instead of the field. Aerial photographs provide a reliable source
for scale measurements of the channel meander geometry. The following
data is collected for each site:
1.
2.
3.
4.
5.
Channel Sinuosity
Meander Length
Belt Width
Radius of Curvature (sometimes measured in field)
Meander Width Ratio
Profile
A longitudinal profile is surveyed for each gage site. Survey shots are taken
along the thalweg for at minimum distance of one meander length. At each
survey point along the thalweg, the elevation of the thalweg, edge of water,
and bankfull elevation is documented. Longitudinal profiles vary from site to
site depending on the dominant sediment size. Streams dominated by sand
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(e.g. Republican, Kansas, Arkansas, and Ninnescah Rivers) typically do not
have a prevalent riffle-pool sequence. Streambed sand is constantly moving
and shifting which creates an undulating streambed with few dominate
streambed sequences. In such cases, water surface slopes are only
determined from the profile. Otherwise, the following data is determined from
each longitudinal profile:
1.
2.
3.
4.
Average Water Surface Slope
Riffle Slope and Pool Slope (if applicable)
Riffle / Pool Sequences (if applicable)
Bankfull Stage Slope
Riparian Condition
There are two visual assessments completed at each site. They are Proper
Functioning Condition (PFC) and Stream Visual Assessment Protocol
(SVAP). The US Department of Interior, Bureau of Land Management (BLM)
and the US Department of Agriculture, Forest Service (FS) and Natural
Resources Conservation Service (NRCS) developed the guide for PFC.
SVAP was developed by the US Department of Agriculture, Natural
Resources Conservation Service.
The PFC guide was developed to qualitatively assess how well the physical
processes are functioning in riparian and wetland areas. This assessment
uses a checklist to synthesize information that is foundational to determining
the overall health of a riparian or wetland system (Prichard et al. 1998). The
checklist is divided into three categories, hydrology, vegetation, and
erosion/deposition. Each section has a series of yes/no questions and then a
summary determination that rates the function of the riparian-wetland area.
SVAP is used to provide a basic level of stream health evaluation (USDANRCS, 1998). It differs from the PFC assessment in that the user determines
a rating based on a variety of physical conditions. The assessment provides a
series of scores ranging from poor to excellent to describe each section.
There are some conditions that may not be rated, so the final score is the
overall score divided by the number of physical conditions scored. Both of
these assessments are used because they are reliable, reproducible, and are
consistent without being extremely time consuming. These assessments also
provide an overall picture of the health of riparian or wetland areas state wide
and when performed over time, will show trends or changes in condition.
Sediment Sampling
The final measurement taken is sediment sampling. One of a stream’s
functions is to move sediment through the watershed. This is a very important
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function of the stream corridor system. Sediment is listed as one of the
pollutants of concern for Total Daily Maximum Loads (TMDLs) determination.
Little rigorous sediment data has previously been collected for Kansas
steams. Collecting sediment is a procedure that requires a great deal of time
and a variety of flow conditions per site. Each stream has the ability to carry a
specific sediment load for a given discharge. Thus, it is important to develop a
sediment rating curve per site. This rating curve relates sediment discharge
as a function of stream discharge. One goal of the current project is to
establish a sediment collection network. Additional time is needed beyond the
current grant’s term to accurately collect data and understand the role of
sediment in Kansas’ river basins.
One goal of this project was to collect sediment samples at each survey site.
Because of the current grant’s term, not every survey site was chosen for
sediment collection. When sediment is collected, the technique used is the
equal discharge increment method for suspended sediment, and the unequalwidth-increment method for bedload discharge (Edwards and Glysson, 1999).
These methods require fewer samples at each cross section and the samples
are located along the cross section in order to delineate equal portions of the
cross section discharge.
On some sites, with high erosion potential, rebar pins are driven flush into an
eroding streambank to measure the rate and volume of erosion. Following a
high flow event, any exposed pins are measured and then driven back into
the bank. This data provides a two-dimensional quantity of materials lost.
Multiply the height and depth of soil lost by the length of the eroded bank
provides a volume of eroded soil. This process provides information on the
location of sediment sources and can provide information for stabilization site
prioritization. Most monitoring sites are placed in areas where local interest in
erosion monitoring exists. This assures someone can measure the amount of
eroded material after each high flow event.
Project results
The results of the dimension, pattern, and profile data will develop several geomorphic
conclusions. One will be a stream classification system for the state. David L. Rosgen
developed the stream classification used in this project. The classification system uses
a morphological documentation of stream characteristics and groups then into relatively
homogeneous stream types (Rosgen, 1994). Rosgen (1996) developed the stream
classification with these specific objectives:
1. Predict a river’s behavior from its appearance.
2. Develop hydraulic and sediment relationships for a stream type and its
state.
3. Provide a mechanism to extrapolate site-specific data to stream reaches
having similar characteristics.
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4. Provide a consistent frame of reference for communicating stream
morphology and condition among a variety of interested parties
This project will provide Kansans with a stream classification system that can assist in
organizing and grouping river data into categories of similar channel morphology. The
database will help communicate information on this important and complex natural
resource.
Another project outcome is the development of regional runoff curves. Regional curves
are data supported graphs that are used to determine the bankfull discharge for
ungaged stream locations. The first step in regional curve development is delineating
hydro-physiographic regions within the state. Hydro-physiographic regions are drainage
basins that have similar climate and geology. Streams in particular regions have strong
linear relations between drainage area and bankfull channel dimensions. This
information can be used to help determine the bankfull flow and channel dimensions on
ungaged streams, when a drainage area is known. The goal is to continue refining them
as more data is collected. New data will help increase the linear relationships and divide
the state into proper hydro-physiographic regions.
Sediment samples analysis, suspended and bedload, will quantify the concentration of
sediment for a given discharge. This portion of the current project will help determine
the volume of sediment moving through a watershed. Eventually, with continuing data
collection, sediment rating curves can be developed for all Kansas streams.
Conclusion
The current project’s main goal is to increase the state’s knowledge on stream corridor
systems. In return, the knowledge will help us better understand stream processes and
develop solutions to repair impaired stream corridors. This knowledge can be brought to
bear when a member of the agriculture or urban community is seeking assistance to
improve stream corridors. Project information dissemination is an important part of the
research effort. We hope that sharing this information will allow others to improve
stream conditions and provide them with information for proper stream corridor
management.
References
Edwards, T.K. and Glysson, G.D. 1999. Field Methods for Measurement of Fluvial
Sediment. U.S. Geological Survey Techniques of Water-Resources
Investigations, Book 3, Applications of Hydraulics, Chapter C2. 89 pp.
Prichard, D., Anderson, J., Correll, C., Foggs, J., Gebhardt, K., Krapf, R., Leonard, S.,
Mitchell, B., and Staats, J. 1998. Riparian Area Management: a user guide to
assessing proper functioning condition and the supporting science for lotic areas.
TR 1737-15. Bureau of Land Management, BLM/RS/ST-98/001+1737, National
Applied Resource Sciences Center, CO. 126 pp.
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Rosgen, D.L. 1994. A Classification of Natural Rivers. Cantena, Vol. 22. pp. 169-199.
Rosgen, D.L. 1996. Applied River Morphology. Wildland Hydrology. Pagosa Springs,
CO. 352 pp.
USDA Natural Resource Conservation Service. 1998. Stream Visual Assessment
Protocol. Technical Note 99-1. NRCS National Water and Climate Center,
Portland, OR. 34 pp.
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