HYDROGRAPHIC SURVEYING TO IDENTIFY THE GEOGRAPHIC DISTRIBUTION OF SEDIMENTS AND SUBAQUEOUS SOILS IN CLOPPER LAKE

Naturally occurring fluvial processes transport sediments through flowing water. This natural process is impeded when dam construction inhibits the ability for a water body to efficiently transport sediment loads. As a result of this process, sediment is deposited in reservoirs which decrease the storage capacity of the water body. Sediment that accumulates in shallow water environments can undergo a process which enables it to support aquatic life (Subaqueous Soils), while sediment that is deposited in deeper portions of the reservoir may need to be removed by dredging in order to extend the life of the dam. In either case, knowing the geographic distribution of these materials can help to create a comprehensive reservoir/dam management plan. Unfortunately, mapping the locations of these materials can be costly and can involve extensive intrusive subsurface investigations. This case study explores the use of remote sensing techniques such as bathymetric mapping, sub-bottom profiling and side scan sonar in an attempt to map the distribution of both subaqueous soils and sediment without the need for costly intrusive investigation. The project was conducted on Clopper Lake, a 90 acre impoundment located in Gaithersburg Maryland. The results of each remote sensing technique are analyzed in a Geographic Information System (GIS) environment in an effort to identify trends occurring in the fluvial processes. This paper presents the challenges, pitfalls and successes of each method and presents the results of the analysis, including the interpreted locations of both subaqueous soils and sediment accumulations.