Chapter Nine Shore Processes and Deposits Associated with Exceptional Events

Abstract

Patterns of evolution of many shorelines are dominated by exceptional storms, especially in terms of shore-normal profile adjustment and shoreline migration. As Forbes, Parkes, Manson, and Ketch have stressed, exceptional storms play a major role because, among other effects, wave power is a quadratic function of wave height; surges associated with such exceptional storms raise the level of wave attack on the shore; higher water levels enable waves of a given size to shoal and penetrate farther landward; setup, run-up, overtopping, and overwash are enhanced during storms; more energetic near-bed current velocities and shear stresses occur during storms; and the foregoing effects can produce exceptionally high sediment transport rates and rapid profile change. Processes generated by exceptional storms include shoreface sediment mobilization and adjustment of the nearshore profile, beach, dune and cliff erosion, barrier breaching and overwash, and longshore modifications that may affect tidal inlets. Understanding storm-induced processes is not only important in terms of coastal management, but is also fundamental in palaeoenvironmental shoreline reconstructions.