Water Resources Research Act Program

Details for Project ID 2008SC55B

Assessing suspended sediment transport potential and supply in an urbanizing coastal plains stream

Institute: South Carolina
Year Established: 2008 Start Date: 2008-03-01 End Date: 2009-02-28
Total Federal Funds: $31,465 Total Non-Federal Funds: $75,983

Principal Investigators: Anand Jayakaran, Susan Libes

Project Summary: Non-point source pollution is an issue that seriously impacts the use of the states water resources for aquatic life use, recreational use, and for shell fish consumption. Almost 60% of the States rivers appear on the 303(d) list of polluted waters for bacterial pollution; further impairment by suspended sediments is also widely seen in many of the water courses. The Crabtree Canal is located in an urbanizing watershed, currently on the 303(d) list for fecal coliforms. The stream was also on the 303(d) list for dissolved oxygen in 2000. An analysis of data measured over the last two years at a USGS gage located at the watershed outlet shows that dissolved oxygen and turbidity are still sources of impairment in the Crabtree Canal. Principal sediment inputs are landscape sources due to land development activities, in-channel sources as a consequence of channel maintenance activities, and from bank instabilities due to increased peak flows that result from watershed urbanization. Evidence of bank instability and mass wasting is widely seen in the Crabtree Canal system. The watershed has undergone considerable urbanization in the last few decades. The study aims to provide a working management tool to determine hydrodynamic conditions on the watershed driven by hypothetical storm events and alternative ditch management techniques. The tool will aid the Horry County stormwater department determine potential zones of stream instability, and evaluate alternate stream management techniques. Changes in flow regime will be quantified as alterations to peak flows, flow stages, and average channel velocity; changes in sediment transport capacity quantified in terms of changes in stream power, and average shear stresses on the channel bed and banks. In conjunction with determining the sediment transport potential, the current availability of sediment for transport by flowing water in the Crabtree Canal system will be assessed. By determining both the ability of a stream to transport sediments, and the availability of sediments to be transported, a better understanding of sediment transport rates can be attained. Additionally, the quantification of the amount of organic material associated with sediments is an aspect that could shed some light on the dissolved oxygen impairment measured in Crabtree Canal. The overall objectives of this study are to: 1. Develop a hydrodynamic model for Crabtree Canal in the Kingston Lake Watershed to model changes in flow regime and sediment transport capacity with alternative channel configurations. 2. Determine temporal distribution of suspended sediment transport rates at a point in the Crabtree Canal. 3. Determine spatial distribution of sources that supply sediments to the main stem of Crabtree Canal. 4. Relate sediment contributions to organic loadings in the Crabtree Canal.