A profile zonation for seasonal sand beaches from wave climate

Hallermeier, Robert

Available guidance on the seaward limit to the wave-dominated beach profile has a generally inadequate basis in physical processes. The new model developed herein divides the shore-normal profile of a seasonal sand beach into three submarine zones parallel to the shoreline. The middle or shoal zone is intended to be a buffer region where expected surface waves have neither strong nor negligible effects on the sand bottom during a typical year. The shoal-zone boundaries are based on critical values of two Froude numbers giving distinct thresholds in sand mobilization by waves. With these critical values, the limiting water depths to the shoal zone are calculated from local sand characteristics and summary statistics of annual wave climate, assuming linear wave theory and an exponential cumulative distribution of wave height. The shoal zone extends seaward from the maximum depth for erosive cutting of the nearshore by yearly extreme waves to the maximum water depth for sand motion initiation by the yearly median wave condition. Available evidence on nearshore sand movement supports placement within this shoal zone of the seaward limit to appreciable bed activity due to surface waves. Suggested coastal engineering applications for the calculated shoal zone are discussed.

A profile zonation for seasonal sand beaches from wave climate

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