Texture, spatial distribution, and rate of reservoir sedimentation within a highly erosive, cultivated watershed: Grenada Lake, Mississippi

Abstract

While more than 75,000 dams nationwide have served a multitude of purposes over the past 50 years, current emphasis is being placed on decommissioning those aged infrastructures considered environmentally harmful. Grenada Lake, a relatively large flood control reservoir in Mississippi, is located in a highly erodible region of the United States and is fed by historically unstable stream channels. Through a variety of stratigraphic analyses, postimpoundment sediments are identified in the reservoir, showing that the lake has lost a nominal 3% of its flood storage capacity since its inception in 1954. A simple sediment budget constructed for the Yalobusha River's contribution of channel-derived sediments shows that about 76% of this sediment remains stored upstream, about 16% is stored in the reservoir, and about 8% has exited the lake. Sediment delivery ratios, known to be low for relatively large watersheds, appear to be unaffected by upstream channel instabilities and aggressive channelization projects. Copyright 2005 by the American Geophysical Union.