SEDIMENT TRANSPORT AND GEOMORPHOLOGY ISSUES IN THE WATER RESOURCES DIVISION

Proceedings of the U.S. Geological Survey (USGS) Sediment Workshop, February 4-7, 1997

SEDIMENT TRANSPORT AND GEOMORPHOLOGY ISSUES IN THE WATER RESOURCES DIVISION

G.F. Koltun, M.N. Landers, K.M. Nolan, and R.S. Parker

Information needs for sediment data are changing rapidly. Historically, the Water Resources Division provided data and analyses regarding sediment transport and geomorphology issues that dealt primarily with engineering structures in the river environment. Indeed, these early sediment studies contributed substantially to the reputation of the United States Geological Survey (USGS) as a leading agency for assessing the Nation's water resources. Today, the most pressing sediment-related problems are associated with environmental questions such as the transport and fate of attached pollutants, effects of sediment on aquatic biota and their habitat, and changes in sediment transport related to land use change. In short, current sediment issues require that sediment studies now address multiple objectives in water resources management. This change places new demands on sediment transport and geomorphology studies in the USGS and on traditional methods which served the organization so well in the past.

Present and future work in sediment transport and geomorphology in the Water Resources Division is based on the following tenets:

Sediment is the largest contaminant of surface water by weight and volume and has been identified by the United States Environmental Protection Agency as the number one problem threatening America's waterways.
Understanding the fate of sediment-bound pollutants requires an understanding of the transport and deposition of sediment.
The physical system of a river provides the framework for understanding the chemical and biological systems. Increasingly sophisticated studies of the chemistry and ecology of river systems place additional demands on our understanding of the physical system.
Hazards such as debris flows, landslides, and channel changes during floods continue to be a nationwide problem.

Listed below are some current issues confronting the USGS and some examples (listed with bullets) of on-going or recently completed projects that address those issues:

Predicting response to channel or watershed modification -- Channel and (or) watershed modifications can be identified as the primary cause of most anthropogenic sediment issues in the United States. Specific problems associated with this issue include prediction of the impacts of urbanization, agricultural practices, and stream channelization or restoration.

Investigations of sediment response to land use are being conducted by several National Water Quality Assessment (NAWQA) study units across the country.
The effects of urban land uses on stream-water quality and geomorphology are being investigated in many studies in the southeastern U.S., for example in the Upper Chattahoochee River Basin that includes the metropolitan Atlanta area in Georgia (Faye and others, 1980).
Investigations of agricultural land-use effects and the effectiveness of best-management practices are underway in the delta region of Mississippi, in the Beaver Creek watershed in Tennessee, and in two small watersheds in southern Delaware.
A study being conducted in Missouri examines the present state of instability of Ozark streams resulting from long-term land-use changes and their effects on the physical aquatic habitat (Jacobson, 1995).
Many stream channels in southeastern Nebraska were dredged and straightened during the early 1900's. A recent USGS study examined the impacts of these stream modifications (Wahl and Weiss, 1995).
A study being conducted on the Cache River in Illinois examines channel instabilities (thought to be related to channel modifications) that endangers a federally-protected wetland.

Instream mining -- Current issues concerning instream sand and gravel mining are the effects of extraction method, and the amount and timing of extraction on channel response.

A study in the Front Range of Colorado focuses on an area of rapid population growth where the maintenance and development of infrastructure requires large volumes of three resources, aggregate (primarily stone, sand, and gravel), water, and energy. The objective in this study is to provide the public and decision makers with information about the location and characteristics of land, natural aggregate, water, and energy resources.
Sand from the Brazos River is being mined and used for construction purposes in nearby Houston, Texas. The USGS is conducting a study to evaluate the effects of instream sediment removal on channel erosion and on sediment delivery to the Gulf of Mexico where sand is needed to replenish beaches.

Forest fires and floods -- Forest fires are known to play a role in altering the hydrologic regime of an area. Increased flooding and sediment transport is one common consequence. Although research funds are sparse, interest remains in the issue of off-site impacts of forest fires.

Studies are being conducted in Bandelier National Monument, New Mexico, and Custer State Park, South Dakota, to examine the changes in sediment discharge and resulting modifications to the channels following forest fires.
A forest fire and subsequent floods in the Buffalo Creek watershed, Colorado, pointed to the vulnerability of the western portion of this urban corridor. A study in this watershed is being conducted to examine the frequency of such events, the importance of fires and subsequent floods in mountain landscape evolution, and the problems such floods create downstream in the urban infrastructure (e.g. Denver water supply reservoir).

Flood plains -- Flood plains are of interest as a conveyor of water and sediment and as a repository of sediment and associated contaminants.

The flood plain of the Clark Fork, Montana, is impacted by fluvial deposition of fine-grained tailings derived from the Butte-Anaconda mining and smelting district. Objectives of a USGS study are to examine the extent and interaction of the channel and contaminated flood plain, and to develop a physically based model for cut-bank erosion.
Dendro-geomorphic methods are being used in the Kankakee River basin to determine long-term sedimentation rates in the flood plains. and then compare sedimentation rates in natural and channelized reaches.

Regulated rivers -- Sedimentation problems on regulated rivers are considerably different from natural rivers. Problems include: sedimentation in reservoirs, channel effects downstream of dams, dam removal, and in-stream flow requirements for maintenance of channels and fisheries. Reservoirs can profoundly affect the geomorphology of streams that have a large natural sediment load, as the reservoir traps sediment and releases clear water. The resulting downstream geomorphic effects of clear water releases from dams typically includes channel instability (as the channel and banks are eroded to satisfy the sediment carrying capacity of the waters), channel bed armoring, and alteration of habitat (Collier and others, 1996).

In the Black Canyon National Monument, a series of upstream dams has eliminated wide seasonal discharge fluctuations resulting in decreased channel cross-sectional areas, reduced frequency of gravel and cobble bar reworking, accumulation of fine sediments on formerly coarse banks and bars, and increased riparian vegetation encroachment. Changes in channel dimensions and riparian vegetation communities are strongly linked in these environments and an ongoing study is detailing the interaction of flow and vegetation along the channel banks (Auble and others, 1994).
In the Green River below Flaming Gorge Dam, Utah, habitat improvements for an endangered fishery are made by seasonal releases from the dam (Andrews, 1986). In a recent USGS study (Andrews and Nelson, 1989) a 2-dimensional model was used in one critical habitat reach to study how the river adjusts its shape to larger discharges.
A 1996 experimental flood in the Grand Canyon was done to provide data needed to predict the movement of water and sediment during floodflows. Methods for predicting the movement of water and sediment had previously been developed and applied by USGS and other scientists at lower flows. Measurements at flood flows were needed to extend the usefulness of these methods and to provide model verification (Collier and others, 1997).
The USGS is collecting data In the Elwha River basin of northwestern Washington to assess how sediment stored in two reservoirs will be released if, or when, the dams are removed. Removal of these dams could allow a return of an anadromous fishery in this river, but land managers need to understand the possible downstream impacts on habitat and infrastructure from alterations in the sediment transport (National Park Service, 1996).

Channel stability / biological impacts -- Channel stability has long been a impact of channel stability on structures, such as bridges, located in or near the channel. That focus has shifted somewhat in recent years to include concern for biological communities living in or near the channel. Examples of problems with biological implications are: predicting the size of flushing flows for spawning sites and maintenance of backwater areas, identifying the temporal changes in bedload transport for substrate mobility, and analyzing bank stability for riparian environments.

Scour around bridge foundations is the leading cause of failure among more than 487,000 bridges over water in the United States. Field-data collection and research studies have been conducted in 37 states in recent years to address the need for improved scour design techniques and more complete descriptions of channel scour processes. The USGS has compiled nearly 400 measurements of local scour at bridge piers, most collected in the past decade; and has evaluated stream geomorphology and potential channel scour at hundreds of bridge sites for state departments of transportation. Results of this work include an advanced understanding of scour processes, extensive channel-scour data collected during floods, improved instrumentation to collect scour data, and more reliable predictive techniques.
Water rights form the basis of some of the channel maintenance issues in the west. An example is an ongoing study of the Snake River in Idaho where one objective is to determine streamflows necessary to maintain channel islands which are ecologically important habitats. Detailed topographic surveys are utilized in a 2-dimensional hydraulic model to predict velocity distributions around the islands at a variety of flows.
The objective of a USGS project on the Missouri River from Buford, North Dakota, to St. Louis, Missouri, is to determine whether off-channel habitat areas will be sustainable or whether these habitat areas will simply fill with sediment resulting in decreasing conveyance at high stages and increasing the hazard of levee breaks. Such detailed examination of sediment distribution in a reach uses a 2-dimensional model.
The relationship between storm runoff, channel disturbance, and benthic community abundance and structure was the focus of a study recently completed in the Big Darby watershed in Ohio (Hambrook and other, 1996).

Cost efficient methods -- The WRD collects basic sediment data that support interpretive studies conducted by WRD and other agencies. In 1996, sediment data were collected approximately daily at 153 stations across the U.S. That number represents a decrease of about 30 percent in the number of daily sediment stations that were operated a decade ago. The reduction in basic data collection has occurred despite the fact that many difficult questions regarding sediment transport and deposition continue to be asked. One reason often given for the decline in basic data collection is the associated cost.

A time series of optical back scattering data is being used as a less-expensive surrogate for suspended-sediment concentrations in San Francisco Bay. These optical back scattering data are being collected to better understand processes responsible for release and transport of sediment in San Francisco Bay.
The USGS program SEDCALC, which is used to compute records of daily sediment discharge, is being upgraded to provide new functionality and to provide a more friendly and efficient user interface.
A new sediment laboratory computer program is being developed at the USGSÕs Cascades Volcano Observatory. This program promises to improve the efficiency of laboratory operations.

Sediment as a conveyor of contaminants -- Evaluation of water-quality conditions and mass transfer of chemical constituents in the Nation's rivers are important parts of the USGS programs. Fluvial sediment is possibly the continentÕs most important contaminant and the medium by which large amounts of toxic substances are transported. The association between the transport of trace metals and sediment is so strong that the seasonal and annual transport of most trace metals can be estimated from sediment flux.

Sediment-associated contaminant transport is of concern within all four WRD regions. Nutrients, metals, pesticides, organics, and (or) radionuclides bound to sediments pose ecological and human health risks in watersheds throughout the Country. Several active interpretive studies in the U.S. have the determination of sediment and associated contaminant loads as a major element. The objectives of these studies are varied and include such goals as to (1) characterize the hydrogeology and water chemistry of watersheds, (2) assess the trophic state of lakes, and (3) provide information on which to base stream restoration strategies.

A project is under way in Wisconsin to assess the influence of vegetated filter strips on the transport of sediment and nutrients to a stream.
Detailed measurements of sediment and water chemistry are being made in several Massachusetts lakes to help assess their trophic state.
The WRD has an ongoing investigation in the southeast Region to develop and document the capabilities and procedures required to investigate and delineate the concentration and partitioning of inorganics with sediments. One product of this project was the development of a part-per-billion protocol used by the USGS for contamination-free collection and processing of whole water samples for the subsequent determination of dissolved trace elements. Effective methods have also been developed for the total trace element analysis of sediments (Horowitz, 1991).
The WRD, in partnership with Geologic Division, plans to study how much sediment is stored in the active channel of the Boise River, Idaho. These data will be used to develop a long-term assessment of storage and release of contaminants.
Investigations of water, energy, and biogeochemical budgets are being conducted at the Luquillo Experimental Forest, Puerto Rico, and at Panola Mountain, Georgia. The project at Luquillo Experimental Forest is comparing chemical weathering, erosion, and mass wasting processes in two tropical rain forest watersheds in the two dominant local rock types, volcaniclastic and quartz diorite. The project at Panola Mountain is investigating processes that control the movement and solute composition of water along hydrologic pathways that produce streamflow in a forested Piedmont watershed. See Couch and others (1996), Faye and others (1980), and U.S. Department of Agriculture (1996) for additional information.
California and Nevada WRD Districts continue to collect data on sediment being supplied to Lake Tahoe by tributary streams. Nutrients adsorbed to sediment have been blamed for increasing biological activity in the Lake, which in turn reduces lake clarity.
A study to characterize the physical, chemical, and biological processes that affect metals in acid mine drainage was conducted in the upper Arkansas River. That study identified colloidal-sized materials as a significant conveyor of trace metals (Kimball and others, 1995). Detailed transport modeling in short reaches of the channel has been used to further characterize the geochemistry (Broshears and others, 1996).

Natural hazards -- Life-threatening hazards that result from the occurrence of rare events remain an important focus of the USGS. The public relies on the USGS to assess hazards before, during, and after they occur. Such hazards include debris flows triggered by heavy rainfall or following volcanic eruptions, landslides on slopes destabilized by road or building construction, dam-break floods, surging glaciers, and earthquakes.

Landslide hazards assessment is a component of ongoing investigations in Puerto Rico and Alabama.The Federal Emergency Management Agency has asked WRD and the Geologic Division to study landslides triggered by the January 1997 floods in Idaho where landslides and debris flows closed some roads and dammed some streams.
Documentation of the recovery of channel systems following eruption of Mt. St. Helens in 1981 continues at the Cascade Volcano Observatory (CVO). Personnel at CVO are also doing basic research on debris flow behavior and assessing flood and debris-flow hazards associated with other Cascade and Alaskan volcanoes

Coastal processes -- Erosion of coastal areas and loss of adjacent wetlands are important management issues. Accelerated coastal erosion results from both natural and man-induced factors including: saltwater intrusion, subsidence, sea level rise, wind-blown surges, upstream channel modification, mineral extraction activities, navigation and drainage projects, and agricultural practices. Information integral to the understanding of this erosion problem is the movement and storage of suspended sediment in the coastal estuaries and slow-moving rivers that border the coast.

Wetlands interactions -- The maintenance of wetlands and their role in trapping and removing sediment and other contaminants are important water resource issues. Determination of wetland sediment budgets is paramount to our ability to understand and maintain wetland functions.

Current sediment issues, such as those discussed above, suggest that much remains to be learned within the topic areas of sediment and geomorphology. Consequently, there is continued need for high-quality sediment data of both a long-term and short-term nature. In order to better address current (and future) sediment and geomorphology issues, we must seek out improved methods of data collection and analysis to meet the broader sampling and data requirements imposed by their multidisciplinary nature. At the same time, we must pursue every efficiency in order to gather necessary data and operate within the present budgetary climate.

SELECTED REFERENCES

Andrews, E.D., 1986, Downstream effects of Flaming Gorge Reservoir on the Green River, Colorado and Utah: Geological Society of America Bulletin, v. 97, p. 1012-1023.

Andrews, E.D., and Nelson, J.M., 1989, Topographic response of a bar in the Green River, Utah, to variation in discharge, IN Ikeda, S., and Parker, G. (eds), River Meandering: American Geophysical Union, Water Resource Monograph 12, p. 463-485.

Auble, G.T., Friedman, J.M., and Scott, M.L., 1994, Relating riparian vegetation to present and future streamflows: Ecological Applications, v. 4, n. 3, p. 544-554.

Broshears, R.E., Runkel, R.L., Kimball, B.A., Bencala, K.E., and McKnight, D.M., 1996, Reactive solute transport in an acidic stream: Experimental pH increase and simulation of controls on pH, aluminum, and iron: Environmental Science & Technology, 30, p. 3016-3024.

Collier, M.P., Webb, R.H., and Andrews, E.D., 1997, Experimental flooding in Grand Canyon: Scientific American, January 1997, p. 82-89.

Collier, M., Webb, R.H., Schmidt J.C., 1996, Dams and Rivers - A primer on the downstream effects of dams: U.S. Geological Survey Circular 1126

Couch, C.A., Hopkins, E.H., and Hardy, P.S., 1996, Influences of environmental settings on aquatic ecosystems in the Apalachicola-Chattahoochee-Flint River Basin: U.S. Geological Survey WRI 95-4278

Faye, R.E., Carey, W.P., Stamer, J.K., and Kleckner, R.L., 1980, Erosion, sediment discharge, and channel morphology in the Upper Chattahoochee River Basin, Georgia: U.S. Geological Survey Professional Paper 1107

Hambrook, J.A., Koltun, G.F., Palcsak, B.B., and Tertuliani, J.S., 1996, Hydrologic disturbance and response of aquatic biota in Big Darby Creek Basin, Ohio: U.S. Geological Survey Water-Resources Investigation 96-4315, variously paginated

Horowitz, A.J., 1991, A primer on sediment-trace element chemistry, 2nd rev. ed., Lewis Publishers, ISBN 0-87371-499-7, 136p

Jacobson, R.B., 1995, Spatial controls on patterns of land-use induced stream disturbance at the drainage-basin scale--an example from gravel-bed streams of the Ozark Plateaus, Missouri: Costa, J.E., Miller, A.J., Potter, K.W., and Wilcock, P.R., eds., AGU Geophysical Monograph 89, The Wolman Volume, p. 219-239

Jobson, H.E. and Andrews, E.D., 1990, Major sedimentation issues for the USGS in Hydraulic Engineering Proceedings 1990 National Conference, San Diego, Highway Division of ASCE, pp.1009-1014.

Kimball, B.A., Callender, E., and Axtmann, E.V., 1995, Effects of colloids on transport in a river receiving acid mine drainage, upper Arkansas River, Colorado, USA: Applied Geochemistry, v. 10, p, 285-306

McKenney, R., and Jacobson, R.B., in press, Erosion and deposition at the riffle-pool scale in gravel-bed streams, Ozark Plateaus, Missouri and Arkansas, 1990-95: U.S. Geological Survey Open-File Report.

Meade, Robert (editor), 1996, Contaminants in the Mississippi River 1987-1992: U.S. Geological Survey Circular 1126.

National Park Service, 1996, Elwha River ecosystem restoration implementation: Final Environmental Impact Statement, Olympic National Park, Denver Service Center, Denver, Colorado, 281 p.

U.S. Department of Agriculture, 1996, The Southern Appalachian assessment aquatic technical report: U.S. Department of Agriculture, Washington, D.C.

Wahl, K.L., and Weiss, L.S., 1995, Channel degradation in southeastern Nebraska Rivers: ASCE Proceedings of the Watershed Management Symposium, San Antonio, Texas, p. 250-259.

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