Lateral variability of overbank sedimentation on a Devon flood plain

Abstract

Deployment of sediment traps over a 12-month period has enabled investigation of the lateral variability of overbank deposition rates and particle size composition of deposited sediment across a frequently inundated flood plain section of the River Culm, southeast Devon, UK. Although a general exponential decrease in deposition rate and grain size with distance from the channel occurs, significant deviations from these trends are associated with the microtopography of the flood plain and secondary flow routes and, in particular, with ditches. The coarsest material and the greatest variability in deposition rates occur within a few metres of the channel. Similar trends are evident for mean particle size, percentage silt and clay, arithmetic sorting and skewness. These parameters also display substantial variation at the distal margins of the flood plain due to the presence of drainage ditches.