Compartmentalisation of beachface sediments along the southwestern coast of Australia

Abstract

Identification of littoral cells is a prerequisite for the determination of sediment budgets on sandy coasts. In this context, the aims of the project were, first, to investigate the applicability of statistical techniques, particularly auto-correlation and cluster analysis, to the definition of littoral cell boundaries; second, add detail to sedimentological and environmental observations previously reported for the southwestern Australian coast; and third, provide a basis for future examination of sediment transport in a nearshore environment that is generally subject to low wave energy. The alongshore component of sediment compartmentalisation has been determined for the sandy beaches of the study area and relationships between environmental parameters and beachface sediment characteristics have been established. Using data describing textural and compositional attributes, the systematic alongshore variation in sediments was determined from the cluster analysis and auto-correlation. Results from the grouping of sediments were then used in conjunction with geomorphic variables to determine boundaries of six sediment compartments. Littoral cells are better developed on the southern sector of the coast where shoreline salients and headlands are larger and act as boundaries. These barriers limit, but do not prevent, inter-compartment sediment transport. The findings of this study provide a context for further investigation of littoral cell dynamics and coastal sediment transport. The statistical techniques applied to data describing the alongshore distribution of sediments are readily repeatable in other contexts and have general applicability and offer a rigorous procedure for definition of coastal regions.