2007 Annual Report
1a.Objectives (from AD-416)
The prime objectives of the agreement are to (1) identify-cost effective solutions for protecting levees of commercial aquaculture ponds and irrigation reservoirs, streambanks and edge-of-field gullies from accelerated erosion by hydraulic and geotechnical processes in highly erodible soils of Mississippi, (2) predict sediment-transport capacity of diffused and concentrated flows, and (3) determine magnitude, frequency and duration relations for sediment transport for stable streams in the southeastern United States.
1b.Approach (from AD-416)
ARS and the University of Mississippi will conduct field and laboratory studies of erosion processes, rates and controlling variables responsible for accelerated erosion of levees, streambanks and edge-of-gullies. Cooperative work will utilize the hydraulic laboratory facilities of the ARS National Sedimentation Laboratory to conduct tests on physical models of typical levees and document the effectiveness of various mechanical treatment alternatives that serve to dissipate wind-wave energy and are cost effective. Data from laboratory and field testing facilities will be analyzed to develop improved predictors of fractional sediment transport rates for diffused and concentrated flows. Historical flow and sediment-transport data from streams throughout the southeastern United States will be sorted by ecoregion and relative stability to determine "background" rates of suspended-sediment transport.
This report serves to document research conducted under a Specific Cooperative Agreement between ARS and the Civil Engineering Department of the University of Mississippi. Additional details of research can be found in the report for the in-house project 6408-13000-017-00D, "Integrated Assessment and Analysis of Physical Landscape Processes that Impact the Management of Agricultural Watersheds." During FY 2007, laboratory experiments on floating wave barriers were continued. Extensive tests of many different geometries, mooring techniques, and levels of buoyancy were performed using the instrumented, automated wave flume constructed for this project. The resulting data were processed, yielding a preliminary best design consisting of a combination of plastic irrigation pipe sizes restrained by vertical pilings. This design was successfully field tested in Schafer Lake, near Carlisle, Arkansas. Visual observations of reduced wave heights were confirmed by measurements of wave height/energy that showed significant reductions. Monitoring was accomplished through regular email, telephone contact, and, when appropriate, site visits. At appropriate stages in the project, progress has been documented by the preparation of reports, conference proceeding papers, and journal articles.