1 Dec 2022

Evaluation of Cedar Tree Revetments for Bank Stabilization at the Locust Creek Conservation Area, Missouri: Quantifying Bank Erosion Volumes from Preproject to Postfailure

Abstract: The US Army Corps of Engineers Regional Sediment Management (RSM) program funded research to assess the longevity and effectiveness of cedar tree revetments for sediment reduction. Between 1988 and 1997, the Missouri Department of Conservation (MDC) constructed multiple cedar tree revetments, plantings, and a grade-control structure at an experimental stream management area on Locust Creek within the Locust Creek Conservation Area (LCCA). For the first few years, MDC also replaced missing trees as needed. MDC monitored these sites with photographs and cross sections until 2004. This study evaluated bank stability on Locust Creek from 1970 to 2019 using aerial imagery, lidar, ground surveys, and a December 2019 site visit to estimate the areal change in streambanks and the volume of sediment eroded over the years. Based on their dates of construction, the project compared preproject, with-project, and postfailure conditions at each site. The project included cedar tree revetments, other hardwood revetments, plantings, and a grade-control structure. This research found a 50% to 64% reduction in erosion for approximately 14 years. As of December 2019, all tree revetments had failed, and banks were bare and steep. The grade-control structure remained intact and continued to stabilize bed and banks immediately upstream.

31 Aug 2022

Sediment Supply from Bank Caving on the Lower Mississippi River, 1765 to Present

Abstract: Bank caving rates and associated total sediment supply were calculated along the Lower Mississippi River from Cairo, IL, to Baton Rouge, LA, using historical maps between 1765 and 1992. Comparison of these maps reveals that the added sediment loads from bank erosion have greatly declined through time. In the pre-1960s period, erosion rates generally ranged from approximately 300 million cubic yards (MCY) to 400 MCY, with the 1880–1930s period having the highest erosion rates of approximately 600 MCY. By the 1990s, the sediment supply from bank erosion was essentially eliminated, with significant erosion being observed at only a few locations, totaling approximately 40 MCY/year. This equates to approximately a 90% reduction in the amount of total sediment being supplied to the channel system from bank erosion.