Tide effects on wave attenuation and wave set-up on a Caribbean coral reef

The effects of tides on wave attenuation and wave set-up were investigated at Great Pond Bay, a Caribbean reef located in St Croix, U.S. Virgin Islands. Measurements of wave pressure fluctuations were made at three stations across the reef profile. Total wave set-up was measured between the forereef and the reef crest or backreef lagoon. Wave spectra indicate significant filtering of energy at the peak frequencies as waves traveled across the reef. The energy dissipation calculations imply an average energy reduction of 62% between the forereef and reef crest. Mean energy reduction between the forereef and lagoon was 90%. Energy dissipation between the forereef and reef crest increased 15% between high and low tide and 6% between forereef and lagoon. Tidal reduction of water depth at the reef crest intensified wave breaking and this condition increased energy dissipation. Measurements of wave set-up ranged from 0.8 to 1.5 cm. Calculations of wave set-up using Tait's 1972 model showed good agreement with observations. (C) 1998 Academic Press.