Suspended Sediment in the Swash Zone: Heuristic Analysis of Spatial and Temporal Variations in Concentration

Abstract

Abstract Swash zone sediment transport is generally measured in an Eulerian reference frame, but this approach tends to give insufficient information on spatial transport characteristics. This paper utilizes a novel technique to map measured suspended sediment concentrations (SSC) onto the x–t plane, thus providing a visualization of SSC at all locations throughout a swash cycle. The widely adopted energetics or bed shear stress approaches to modeling suspended sediment transport in the swash predict that SSC varies directly with the horizontal velocity, u, to the power of either 2 or 3. A calibrated ballistic swash model was used to predict SSC(x,t) ∝ u2 and SSC(x,t) ∝ u3. The qualitative comparison between field measurements and transport model predictions in x–t space provides the opportunity to examine the transport model performance throughout the swash zone. The agreement between observed and modeled SSC patterns was generally poor. Similar to previous observations, SSC was larger during the uprush ...