Spatial Variability of the Particle Size Composition of Overbank Floodplain Deposits

An important feature of overbank floodplain deposits is the spatial variability of their particle size composition. Analysis of such spatial variability can assist in developing an improved understanding of the transport and deposition of suspended sediment on river floodplains during overbank flood events, in investigating the fate of sediment-associated contaminants and in calibrating existing floodplain sediment deposition models. The study reported in this paper investigates the spatial variability of the grain size composition of overbank floodplain deposits at different spatial scales, through analysis of surface sediment samples collected from frequently inundated floodplain sites on the Rivers Cuhn, Stour and Severn in the UK. Significant lateral and downstream variations in the grain size composition of the sediment deposits have been documented at the study sites, and the results obtained have been interpreted in terms of the processes governing overbank floodplain flow and sediment transport and deposition, which are influenced by a number of factors including floodplain geometry and topography.