SEASONAL-SCALE PROCESSES OF SEDIMENT ACCRETION AND RETENTION IN A DIVERSION-FED MISSISSIPPI DELTA WETLAND

River deltas are some of the most dynamic environments on Earth, constantly reshaped by competing riverine, atmospheric, and tidal forces. While the evolution of existing deltas follows a well-understood cyclic process, little is known about the early stages of individual crevasse initiation. Today, many large rivers are heavily engineered to prevent channel switching, reduce flooding, or enhance navigation. Development of new crevasse splays has become rare and thus difficult to observe in the field. One exceptional location to study crevasse initiation in the field is in the receiving basin of Davis Pond Freshwater Diversion on the lower Mississippi River. Completed in 2002, Davis Pond diversion supplies pulses of freshwater and sediment to the surrounding marsh during scheduled high flow events. Recently, new land has emerged at the mouth of its outfall channel. In this study, we examine seasonal-scale patterns of sedimentation in the Davis Pond receiving basin. Sets of twenty-two short (5 cm) sediment cores were collected immediately following and six months after a two-week opening of the diversion (April 2015 and October 2015, respectively). Cores were analyzed for organic content, bulk density, and grain size. Activities of the radioisotope beryllium-7 were used to calculate sediment accumulation and retention rates. This work leads to the development of a sediment budget for the Davis Pond system and an analysis of restoration potential in the subsiding deltaic wetland. Lower Mississippi River diversions such as Davis Pond reconnect the river to its floodplain, mimic the land-building processes of natural crevasse splays, and provide a promising method to combat land loss in coastal Louisiana.