Control of Sediment Deposition at Big Sandy Draw Bridge and Interstate 20

摘要

The objective of the study was to identify causes and recommend remedial measuresfor the sand deposition at the Big Sandy Draw bridges on Interstate 20. The source of the sand is both water and wind erosion on the 11.3 sq mi watershed. Deposition in the vicinity of the bridges is caused by severe backwater from Beals Creek, located about one-quarter mile downstream. Two historical and the one, two, ten, twenty-five, fifty, and one-hundred year precipitation events were modeled using HEC-1. Yang's sediment transport equation was used to estimate the sediment load for each of these events. HEC-2 was used to determine a rating curve above the bridges. The FEMA study data was used to set the Beals Creek water surface for concurrent flow in Big Sandy Draw and Beals Creek. Based on the results of the study, a basin 400 ft long, 200 ft wide and 12 ft deep will just accommodate the 100-year event. Due to the stochastic nature of the rainfall/runoff no definitive recommendation can be made about basin size. A smaller basin will require more frequent removal of the sediment. Right-of-way and access requirements will likely dictate the best basin size.