Effects of bed-form roughness on long-wave transformation over fringing reefs

Abstract

This thesis presents the formulation and implementation of a series of flume experiments to investigate long-wave transformation over bed-form roughness in fringing reef environments. The experiments were carried out in the Large Wave Flume at the O.H. Hinsdale Wave Research Laboratory, Oregon State University that measures 104 m long, 3.66 m wide, and 4.6 m high. A reef model has a 1:12 face slope and a long flat for investigation of wave shoaling and breaking as well as bore development and propagation. The model is 2.36 m tall and the water depth ranges from 2.36 to 2.66 m to reproduce dry and wet reef conditions. The bed-form roughness is modeled by timber beams placed across the flume in four configurations by varying the height and periodicity. The incident solitary wave height varies from 0.05 to 0.5 of the water depth to cover a range of wave breaking conditions. A series of wire and sonic gauges recorded the wave transformation along the flume for different bed roughness conditions a digital camera recorded images of the breaking waves on a background grid painted on a tank wall. The results show significant effects of the bed-form roughness on the shoaling process, the breaking water depth, and the breaking wave height on the reef slope as well as the wave height attenuation and bore speed on the reef flat.