Sand Beach Ecology: Swash Features Relevant to the Macrofauna

Abstract

Aspects of swash climate of significance to benthic macrofauna were studied over 19 tidal cycles on 10 beaches representing a range from reflective to ultra-dissipative extremes. Dissipative beaches typically had slopes of 1:50-1:80, swash periods of 40-60 sec and wave period/swash period ratios about 0.2. Reflective beaches had slopes steeper than 1:15, swash periods of 11-13 sec and wave period/swash period ratios about 0.80. Intermediate beaches typically displayed slopes of 1:25-1:45, swash periods of 15-30 sec and wave period/swash period ratios of 0.4-0.65. Most beaches displayed more reflective characteristics at high tide and more dissipative characteristics at low tide. Control of swash climate was primarily by beach slope and wave height, the former being more important towards the reflective extreme, the latter towards the dissipative extreme and both being critical in intermediate beaches. The implications of different swash climates for beach fauna are discussed.