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

EROSION AND SEDIMENTATION RESEARCH IN THE U.S. DEPARTMENT OF AGRICULTURE, AGRICULTURAL RESEARCH SERVICE

By S.J. Bennett and C.V. Alonso,
USDA-ARS,
National Sedimentation Laboratory,
P.O. Box 1157,
Oxford, MS 38655

Introduction: Mission of the Agricultural Research Service and Historical Perspective

The ARS is the research branch of the USDA, and its mission is to provide access to agricultural information and develop new knowledge and technology needed to solve agricultural problems of national importance to ensure adequate availability of high-quality, safe food and other products, to sustain a viable and competitive food and agricultural economy, to enhance quality of life and economic opportunity for rural citizens and society as a whole, and to maintain a quality environment and natural resource base. Of the six main ARS programs, the Soil, Water and Air division conducts research on conserving and managing our soil, water and air resources to minimize the effects agriculture has on the environment while keeping costs to the consumer low and profits to the farmer as high as possible.

Traditionally, most research has focused on farm management and practices, soil conservation techniques, and the impact of agrichemical transport on water quality and ecology, and how these areas affect farm productivity and sustainability, the socio-economics of farming communities and the preservation of natural resources. To meet these challenges, the ARS established national laboratories and experiment stations throughout the country, and approximately 18 are currently pursuing research on erosion and sedimentation. Each laboratory is staffed with scientists from several disciplines conducting research pertinent to both its geographic location, thus serving the needs of local communities, as well as providing leadership and support for national programs. The major centers for this research are, and will continue to be, the National Sedimentation Laboratory at Oxford, MS, and the National Erosion Laboratory at West Lafayette, IN (1). Several of the ARS Watershed Research Centers are contributors, including the Southwest Watershed Research Center at Tucson, AZ, the Northwest Watershed Research Center at Boise, ID, and the North Appalachian Experimental Watershed at Coshocton, OH. Interests in controlling erosion from irrigated lands has increased in the past decade, and several of the irrigation laboratories are contributing, with the ARS location at Kimberly, ID, providing leadership on this effort. There is, and has been, considerable interest in the development of erosion models and decision support systems for assisting land managers and conservation specialists in their efforts to reduce the adverse impacts of soil erosion on agricultural productivity and the environment. The key ARS locations contributing to this effort are the National Soil Erosion Laboratory, the National Sedimentation Laboratory, the Southwest Watershed Research Center, and the Grasslands Research Laboratory at Temple, TX.

Research on erosion and sedimentation is still firmly rooted in agricultural areas and vicinities, hence soil conservation and farm management practices remain the most active areas of study. Off-site impacts of erosion and sedimentation, a revitalization of fundamental research, and the emergence of integrated, interagency projects have provided greater insight and advanced technologies broader in scope and application than ever realized. Such diversification affords research opportunities in upland areas, streams and channels, and biology and ecology which span scientific, agency, and academic boundaries, improving both the relevancy and visibility of the research in national and international communities.

The Erosion Prediction and Control National Program (2) has been established to provide knowledge and technology by which agricultural activities may be conducted while keeping erosion of soil and attached chemical and biological substances to a minimum. Specific objectives of this program include: (a) developing and evaluating control technologies, such as mechanical (terraces, water flow control structures), vegetative (tree or grass wind breaks, alternating crop strips, stiff grass hedges), or tillage based (conservation tillage), (b) developing and advancing the application of erosion prediction models, and (c) advancing the state-of-the-art with respect to understanding erosion processes.

A number of current research areas within the ARS are briefly described below. This document is limited in scope to the agenda of the workshop, and provides a succinct description of a few key research areas specific to the general area of erosion and sedimentation.

Conservation Farm Management Practices

Tilling farmlands remains the most damaging activity responsible for soil loss and the mobilization of fine-grained material. Conservation tillage systems have been developed to maximize crop production while reducing soil losses, and includes such practices as specialized and alternative tilling procedures, increasing and maintaining surface residue coverage and surface roughness, creating infiltration channels, improving animal management on pastures, and increasing canopy coverage (3). The construction of vegetative barriers, such as stiff grass hedges and grass strips, and the establishment of riparian buffer zones have been proven to reduce soil loss and agrichemical transport from agricultural fields as well as dispersing runoff from areas of concentrated flow (4). In particular, the expiration of the Conservation Reserve Program in 1995, where well-established grasslands are returned to cropland production, poses a major threat for future soil loss and sedimentation problems. Studies have been initiated to quantify the effects of tillage on soil quality and erodibility and to formulate and emplace conservation techniques before conversion takes place (5). The ultimate success of conservation techniques depends not only on proven technology but on farmer participation, socioeconomic perceptions of conservation, and appropriate legislation such as National Practice Standards.

Fundamental Research on Soil Erosion and Erosion by Concentrated Flows

A fundamental understanding of soil erosion processes is a necessary prerequisite for developing adequate erosion-control technology. By using simple outdoor plots and rainfall simulators, the ARS has been a leader in quantifying soil detachment and transport processes and these same tools are in use today. Recent work has focused on better characterization of rainfall erosivity using NEXRAD technology, the effects of surface seal development, soil roughness, aggregate strength and proportion of rock fragments on sediment yield, rill development, rill hydraulics and microtopography evolution, the mechanics of crack formation, the effects of cracks and subsurface pressures on infiltration and runoff, agrichemical partitioning within detached soils, and erosion by head-cut formation and migration (6). New technology, such as non-intrusive acoustic and laser devices, provide greater insight into a soil's physical characteristics, of particular importance in evaluating its strength and erodibility (7). These studies are proving instrumental in developing and testing accurate, physically-based models for soil erosion (see later). Understanding and characterizing spatial and temporal variations in a soil's properties and the impact of antecedent conditions (history effects such as climate, farming practices or biological activities) remain the challenges for future research.

Sediment Transport Mechanics

The entrainment, transport and deposition of sediment has a major impact on erosion and channel stability, channel capacity as related to flood risk, reservoir viability, and in-stream ecology. Field and laboratory investigations have concentrated on the formative processes controlling sediment transport including sorting processes in mixed-size sediments, turbulence and bedform stability, the dynamics of sediment-laden flows, the effect of flow unsteadiness on sediment flux and bed configuration, and the intrusion of fine-grain material into open-framework gravel beds (8). The inability to quantify and predict suspended sediment loads and the need to identify the source of fine-grained sediment, whether from bank erosion or hillslope input, has necessitated employing sophisticated technology and the expertise of academia. A cooperation currently exists to develop an automated, field-based acoustic probe to measure instantaneous depth- averaged suspended loads (9). By coupling new conceptualizations with technology, the ARS is emerging as an invaluable resource for federal agencies and academia.

Channel Adjustment and Evolution

Geomorphic analyses provide detailed information on the dynamics of channel evolution critically important for identifying unstable stream reaches and guiding the placement and choice of stabilization techniques. With more than 75% of the sediment from channel erosion emanating from stream banks in some parts of the country, research on bank stability and channel evolution has focused on the effects of pore pressures on bank strength, the deposition and entrainment of failed blocks of cohesive material, quantifying the volume of material entering the stream through bank failure, and characterizing the dynamics of meanders and redefining the concept of dominant discharge within incised channels (10). Concurrently, scientists have been developing a physically-based numerical model of the evolution of unstable river channel morphology, a model able to simulate the effects of riparian vegetation on flow resistance and bank material properties and failure frequencies (11). Coupled with detailed field experiments, simulations provide a means to investigate the effects of low-cost vegetative bank protection treatments in restored river channels in addition to temporal variations in channel geometry and flow capacity as a guide for effective channel management.

The Impact of Erosion and Sedimentation on Ecology, and Stream Restoration

Agricultural activities have often resulted in the degradation or loss of habitat and habitat resources in adjacent or downstream river corridors and lakes, yet little information exists to assess such impact as well as providing guidelines for restoration. A two-fold approach has been adopted by ARS personnel in cooperation with other federal agencies: (a) experimental projects to determine the effects of agricultural runoff, sedimentation and stream stabilization measures on ecological systems and water quality, and (b) formulating appropriate stream restoration techniques to be used with channel stabilization (12). Recent work has demonstrated that shortages of woody debris, pool habitat, substrates other than sand, and flashy hydrology are the primary deficiencies in physical aquatic habitats in warm-water streams damaged by channel erosion, and these same ecosystems respond positively to certain types of stabilization techniques such as spur dikes, stone weirs, emplacement of woody vegetation, and low-drop grade control structures (12). Constructed wetlands on or near farms can also partition runoff-related agrichemicals and sediments, thus minimizing their impact on stream ecosystems (13). An interagency handbook in preparation, headed by the NRCS with contributions from ARS personnel, will provide complete guidance on planning, designing, and evaluating stream restoration projects (14).

Recent Advances in Modeling Sediment Yield

Models for sediment yield provide invaluable information when applied to those areas lacking of data, for guiding data collection programs in gaged watersheds, and for predicting future impacts of agricultural activities, climate, land-use, stream stabilization and flood control practices. The level of sophistication of current hillslope and watershed models has increased significantly: the integration of GIS and digital elevation models with numerical techniques and physically-based conceptualizations provide for better characterizations of runoff and soil yields, in-stream flow and sediment routing, bank erosion and channel widening, and the effects of changing land coverage, agricultural and engineering practices (15). Cooperations have been established linking national laboratories with state-of-the-art computational centers in academia (16). ARS operational models for natural resource conservation assessments such as the Revised Universal Soil Loss Equation (RUSLE), the Water Erosion Prediction Project (WEPP), Agricultural Non- point Source Pollution (AGNPS), Soil and Water Assessment Tool (SWAT) and Topographic Parameterization (TOPAZ) are continually being improved, tested and expanded (17). These models receive prominent national support at ARS and NRCS locations, and have been implemented throughout the country by both federal and non-federal users. However, the acquisition of reliable field data is imperative for model verification, improvement and applicability. Thus, experimental watersheds, such as Goodwin Creek and Reynolds Creek (18), provide unrivaled long-term data-bases for model formulation and development, and their continued maintenance and viability is of critical importance.

Interagency Cooperations: DEC and MDMSEA

The benefits of interagency cooperations are obvious: synergistic agreements amongst action agencies which pool resources and expertise for immediate response to specific societal needs. Although primarily applied in nature, consortiums offer opportunities to provide leadership and develop technology while expanding the research base and impact of the particular agency. Two current programs involving ARS personnel exemplify the benefits of such cooperations.

The Demonstration Erosion Control (DEC) Project, established in 1984, seeks to develop and demonstrate a watershed or systems approach to address problems associated with watershed instability: erosion, sedimentation, flooding, and environmental degradation. Watersheds in the Lower Mississippi Valley, areas devastated by erosion, channel incision and channel widening, were targeted. Several federal agencies and some universities, each with clear roles, objectives, and expertise are participating including the COE, NRCS, ARS, COE-WES, USGS, and the University of Mississippi. Notable advances in land treatment, stable channel assessment, stream bank erosion, stream habitat restoration, computational and physical modeling of rivers, sediment transport mechanics, and grade control structure design have been recorded in literature published by DEC-affiliate personnel.

The Mississippi Delta Management Systems Evaluation Area (MDMSEA) Project, established in 1994, seeks to design and evaluate best management practices to reduce adverse agricultural impacts on water resources and ecological processes (19). A consortium of 15 federal, state, and local agencies are involved, and the principal agencies are the ARS, USGS, and Mississippi Water Resources Research Institute. The project targeted three research watersheds each comprising an oxbow lake, thus providing closed-systems for integrated research. Although only in use for one year, precision farming techniques have significantly reduced the amount of herbicide required for weed control in cotton and soybean fields. Hence, the proven success and national impact of interagency cooperations will foster new liaisons in the future.

Information Sources (National Program Leaders, Research Leaders and key personnel)

In lieu of detailed references, the interested reader is encouraged to contact the key personnel involved in the specific research.

  1. D. A. Farrell, USDA-ARS, National Program Staff, Building 005, BARC-West, Beltsville, MD 20705.
  2. C.R. Amerman, USDA-ARS, National Program Staff, Building 005, BARC-West, Beltsville, MD 20705.
  3. Residue management: K. McGregor, USDA-ARS, National Sedimentation Laboratory, P.O. Box 1157, Oxford, MS, 38655; L.B. Owens, USDA-ARS, North Appalachian Experimental Watershed, End of State Route 621, State Route 478, Coshocton, OH 43812; D. Wilkins, USDA-ARS, Columbia Plateau Conservation Research Center, P.O. Box 370, Pendleton, OR 97801; Tillage systems and Pasture management: K. McGregor, USDA-ARS, National Sedimentation Laboratory, P.O. Box 1157, Oxford, MS, 38655; L.B. Owens, USDA-ARS, North Appalachian Experimental Watershed, End of State Route 621, State Route 478, Coshocton, OH 43812; J.L. Steiner, USDA-ARS, Southern Piedmont Conservation Research Center, 1420 Experiment Station Road, P.O. Box 555, Watkinsville, GA 30677; D. Wilkins, USDA-ARS, Columbia Plateau Conservation Research Center, P.O. Box 370, Pendleton, OR 97801.
  4. Stiff Grass Hedges: S. Dabney, USDA-ARS, National Sedimentation Laboratory, P.O. Box 1157, Oxford, MS, 38655; K. McGregor, USDA-ARS, National Sedimentation Laboratory, P.O. Box 1157, Oxford, MS, 38655; J.C. Ritchie, USDA-ARS, Hydrology Laboratory, Bldg. 007, Rm. 104, BARC-West, Beltsville, MD 20705; Riparian Zone: A.W. Thomas, USDA- ARS, Southeast Watershed Research Laboratory, P.O. Box 946, Tifton, GA 31793.
  5. Conservation Reserve Program: J. Gilley, USDA-ARS, Soil/Water Conservation Research Unit, University of Nebraska-Lincoln, 119 Keim Hall, East Campus, Lincoln, NE 68583- 0915; K. McGregor, USDA-ARS, National Sedimentation Laboratory, P.O. Box 1157, Oxford, MS, 38655.
  6. S.J. Bennett and C.V. Alonso, USDA-ARS, National Sedimentation Laboratory, P.O. Box 1157, Oxford, MS, 38655; J.L. Hatfield, USDA-ARS, National Soil Tilth Laboratory, 2150 Pammel Drive, Ames, IA 50011; A. Kennedy, USDA-ARS, Agricultural Engineering Department, Washington State University, Room 215, Johnson Hall, Pullman, WA 99164- 6421; L.D. Norton, USDA-ARS, National Soil Erosion Research Laboratory, Purdue University, Soil Bldg., West Lafayette, IN 47907-1196; C.E. Rice, G. Hanson, K. Robinson and D. Temple, USDA-ARS, Hydraulic Engineering Research Unit, 1301 N. Western Street, Stillwater, OK 74075; M.J.M. Romkens, USDA-ARS, National Sedimentation Laboratory, P.O. Box 1157, Oxford, MS, 38655; M.A. Weltz, USDA-ARS, Pacific West Area, Southeast Watershed Research Center, 2000 East Allen Road, Tuscon, AZ 85719-1596.
  7. J.L. Hatfield, USDA-ARS, National Soil Tilth Laboratory, 2150 Pammel Drive, Ames, IA 50011; C.E. Rice, G. Hanson, K. Robinson and D. Temple, USDA-ARS, Hydraulic Engineering Research Unit, 1301 N. Western Street, Stillwater, OK 74075; M.J.M. Romkens, USDA-ARS, National Sedimentation Laboratory, P.O. Box 1157, Oxford, MS, 38655; D. Wilkins, USDA-ARS, Columbia Plateau Conservation Research Center, P.O. Box 370, Pendleton, OR 97801.
  8. C.V. Alonso, S.J. Bennett, and R.A. Kuhnle, USDA-ARS, National Sedimentation Laboratory, P.O. Box 1157, Oxford, MS, 38655.
  9. R.A. Kuhnle, USDA-ARS, National Sedimentation Laboratory, P.O. Box 1157, Oxford, MS, 38655; Robert Derrow, National Center for Physical Acoustics, University of Mississippi, University, MS 38677.
  10. A. Simon and S. Darby, USDA-ARS, National Sedimentation Laboratory, P.O. Box 1157, Oxford, MS, 38655.
  11. S. Darby, USDA-ARS, National Sedimentation Laboratory, P.O. Box 1157, Oxford, MS, 38655.
  12. C.M. Cooper, S.S. Knight, and F.D. Shields, USDA-ARS, National Sedimentation Laboratory, P.O. Box 1157, Oxford, MS, 38655.
  13. C.M. Cooper, S.S. Knight, and S. Testa, USDA-ARS, National Sedimentation Laboratory, P.O. Box 1157, Oxford, MS, 38655.
  14. F.D. Shields, USDA-ARS, National Sedimentation Laboratory, P.O. Box 1157, Oxford, MS, 38655.
  15. J.G. Arnold and R. Srinivasan, USDA-ARS, Grassland, Soil/Water Research Laboratory, 808 E. Blackland Road, Temple, TX, 76502; R.L. Bingner, USDA-ARS, National Sedimentation Laboratory, P.O. Box 1157, Oxford, MS, 38655; J. Garbrecht, USDA-ARS, Southern Plains Area, P.O. Box 1199, El Reno, OK 73093; C.E. Rice, USDA-ARS, Hydraulic Engineering Research Unit, 1301 N. Western Street, Stillwater, OK 74075; A.W. Thomas, USDA-ARS, Southeast Watershed Research Laboratory, P.O. Box 946, Tifton, GA 31793; M.A. Weltz, USDA-ARS, Pacific West Area, Southeast Watershed Research Center, 2000 East Allen Road, Tuscon, AZ 85719-1596.
  16. R.L. Bingner and C.V. Alonso, USDA-ARS, National Sedimentation Laboratory, P.O. Box 1157, Oxford, MS, 38655; S. Wang, Center for Computational Hydroscience and Engineering, University of Mississippi, University, MS 38677.
  17. RUSLE: G.R. Foster, USDA-ARS, National Sedimentation Laboratory, P.O. Box 1157, Oxford, MS, 38655; WEPP: D.C. Flanagan, J.M. Laflen, M.A. Nearing, and L.D. Norton, USDA-ARS, National Soil Erosion Research Laboratory, Purdue University, Soil Bldg., West Lafayette, IN 47907-1196;SWAT: J.G. Arnold and R. Srinivasan, USDA-ARS, Grassland, Soil/Water Research Laboratory, 808 E. Blackland Road, Temple, TX, 76502; TOPAZ: J. Garbrecht, USDA-ARS, Southern Plains Area, P.O. Box 1199, El Reno, OK 73093.
  18. Goodwin Creek Watershed: C.V. Alonso, USDA-ARS, National Sedimentation Laboratory, P.O. Box 1157, Oxford, MS, 38655; Reynolds Creek Watershed: C.W. Slaughter, USDA- ARS, Northwest Watershed Research Center, 800 Park Blvd., Plaza IV, Suite 105, Boise, ID 83712-7716.
  19. J.D. Schreiber, USDA-ARS, National Sedimentation Laboratory, P.O. Box 1157, Oxford, MS, 38655; R. Rebich, USGS, 308 South Airport Road, Pearl, MS, 39208; J. Pote, MWRRI, P.O. Drawer AD, Mississippi State, MS 39762-5529; Frank Gwin, Jr., P.O. Drawer 727, Tchula, MS 39169.

Autobiography

Bennett, S.J., USDA-ARS, National Sedimentation Laboratory, Oxford, MS: For the past 15 months, the incumbent has served as a Research Geologist in the Channel and Watershed Processes Research Unit. His research includes experimental and theoretical investigations of sediment transport of mixed size-density fractions, bedform mechanics, turbulence, dynamics of sediment-laden flows, and erosion by concentrated flow.

Workshop Proceedings
Contributions from Other Federal Agencies
Contribution from the USGS