Sediment Transport Processes on Mixed Beaches: A Review for Shoreline Management

Abstract

Mixed beaches are a comparatively neglected area of coastal research, other than for sedimentological investigations or relatively long-term geomorphological change. The paper reviews the progress of research into processes of sediment transport on mixed sand and gravel beaches since 1980, including fieldwork, laboratory studies and modelling. First order and secondary factors are identified. The hydraulic conductivity of the bulk sediment is found to be an influence on swash and backwash infiltration and groundwater flow through the sediment. No existing transport model contains the most significant factors for mixed sediment transport, which should include swash and backwash hydrodynamics, infiltration, steep beach gradients, fractionation and differential hydraulic conductivity. Near-prototype scale physical model tests of profile response are needed, since mixed sediments cannot be scaled correctly for both hydrodynamic response and hydraulic conductivity.