Wave Transformation on Reef and Some Consideration on Its Application to Field

Abstract

ABSTRACTABSTRACTThe field observation of waves on the reef characterizing the most coasts of the Ryukyu Islands was carried out at Busena Coast, Okinawa Islands, as shown in Fig. 2, and accordingly, model experiments of the wave transformation on the reef were conducted. The data obtained from the field observations were analyzed for statistical and spectral characteristics of waves, and wave transmission coefficients were compared with experimental ones to clarify the applicability of the experimental results to the field.The peak frequency of wave power spectra on the reef is found to be around 0.11 Hz, and the high frequency part of incident wave spectrum (spectrum E in Fig. 4) is very close to the equilibrium spectrum proposed by Phillips. The powers of wave spectra in the reef lagoon decay rapidly. They seem to approach to a constant value as the waves travel on the reef. The wave heights in the reef lagoon decay considerably comparing to the incident wave heights. For the applicability of the model experiments, the parameter, q, which is a ratio of the water depth on a reef to that at offshore side, seems to be the most important factor and the results from the experiments agree fairly well with those from field observations when the value of the parameter, q, becomes large.