Sediment Deposition into a Valley-Margin Lake in a Managed Floodplain, Catahoula Lake, Louisiana, USA

Friday, 19 December 2014
Richard Keim1, Karen Latuso1,2, Ronald D DeLaune1 and David C Weindorf3, (1)Louisiana State University, Baton Rouge, LA, United States, (2)Louisiana Department of Environmental Quality, Baton Rouge, LA, United States, (3)Texas Tech University, Lubbock, TX, United States
Sediment sources to valley-margin lakes vary spatially and temporally depending on relative dominance of the main or tributary rivers. Catahoula Lake is the largest valley-margin lake in the lower Mississippi River Alluvial Valley and is hydrologically influenced by backwaters of the Mississippi and Red rivers and headwaters of the Little River. Our objective was to understand effects of hydrological management of the floodplain and the lake itself on lake sediments and recent changes in vegetation. Comparison of 137Cs profiles with prior 210Pb and 14C profiles indicates the recent deposition rate has been low (0.3 cm/yr) but triple that prior to settlement. Sediment chemistry profiles indicate dominance of acidic coastal-plain sediments from the tributary Little River in the past ~60 yr, but spatially mixed influence of acidic and neutral, Mississippi-Red sediments prior to that. We conclude that a century of increasing hydrologic management of the Mississippi and Red rivers has disconnected Catahoula Lake from their sedimentary influence and that the consequent change in chemical composition of surficial sediments may be contributing to ecologic changes in the lake.