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Title: MODELING THE EFFECTIVENESS OF SILT FENCE

Author
item BRITTON, SHERRY - OKLAHOMA STATE UNIVERSITY
item Robinson, Kerry
item BARFIELD, BILLY - OKLAHOMA STATE UNIVERSITY

Submitted to: Federal Interagency Sedimentation Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 3/25/2001
Publication Date: 3/27/2001
Citation: N/A

Interpretive Summary: Vast quantities of valuable topsoil are lost each year as a result of soil erosion. When sediment reaches a stream or lake it can decrease water quality and harm aquatic life. Drastically disturbed lands, such as construction sites for roads and buildings, are particularly vulnerable to soil erosion. Using silt fences is one method of capturing and retaining sediment on-site. Little information is presently available about how silt fences perform when exposed to sediment-laden flows. This study examined the performance of silt fences exposed to both clear-water and sediment- laden flows. The sediment can plug the openings in the silt fence and substantially decrease the amount of water that passes the fabric. A simplified method was developed to allow the user to predict the flow rate through a fabric. This information should be of interest to the wide range of disciplines charged with reducing soil erosion, minimizing sediment runoff, and improving water quality.

Technical Abstract: Research on three woven silt fence products (fabrics A, B, and C) was conducted to evaluate their effectiveness at separating sediment from runoff water. The three fabrics were tested over a range of flow rates and sediment feed rates. Sediment of known size and gradation was developed from glass beads ranging in size from 1.5 to 177 um. Using a digital encoder, the changes in head against the fabric were measured. From the head information, the flow rate exiting the fabric was determined by calculating the volumetric changes in the model during the recession period of each test. Head versus discharge plots were developed to compare the clear-water and sediment-laden flows of each fabric. Each fabric demonstrated unique clear-water flow behavior. Fabric A was slightly affected by sediment-laden flow, while sediment had a dramatic influence on fabric B. The performance of fabric C fell between the other fabrics. The number and size of the fabric openings were observed to influence how much sediment passed the fabric. Preliminary modeling efforts suggest that a simple modification of the orifice equation fit the data well. The performance of the fabrics was also evaluated based on their trapping efficiencies and average sediment concentrations exiting the flume. This study provides valuable information about silt fence performance and a preliminary model of flow through the fabric.