SOME FACTS AND FANCIES ABOUT BEACH EROSION

Abstract

Coastal defense up to the present has employed seawalls, groynes and renourishment, all of which do not tackle the basic problem of lack in sediment supply from upcoast. The need is for sufficient sand to be continually available for the formation of the defensive offshore bar. If means are provided for this material to be returned directly on shore by subsequent swell, a stable situation 'ensues. Such normal re-deposition occurs within bays formed between headlands which have reached equilibrium shape or nearly so. Comparisons are made between various stabilization procedures. The influence of sand characteristics in renourishment is discussed. Stabilization of coasts has been carried out over many decades. The remedies have taken three major forms, namely, seawalls, groynes, and in more recent times sand renourishment. Whilst shapes and orientation of these structures have been varied in order to optimise protection, engineers in the main have relied upon bigness for greater reliability. Investment in dredging to supply sediment "temporarily" to beaches is growing prodigiously. It is now time to sit back and reassess the situation, so as to determine a change of outlook, be it only slight, that may effect greater long term economies.