Field Observations on Turbulent and Wave Shear Stresses in Surf Zones: Effects from Wave Breaking and Rough Seabed

Understanding the hydrodynamics and turbulent flows is crucial in modeling and monitoring the sediment transport, geological, biogeochemical, and biological processes in nearshore environments. It is difficult to have a quantitative study due to the complex process of wind, waves, tides, wave-current interaction and multi-scale flow dynamics. Based on the up-to-date literature review and our recent efforts, wave-current turbulence in nature rough seabed of coastal environments are largely unexplored. As a result, we propose to study the wave-current turbulence, wave stress under surf-zone breaking waves over nature rough seabed in fields. We have shown the ability and experiences to perform high-quality field experiments to observe turbulent mixing in shallow waters in the challenging coastal zone where waves and currents coexist. In this proposal, field experiments and data analysis will be conducted to explore the mechanisms driving the turbulent mixing under surf-zone breaking waves over the nature rough seabed over an algal reefs, Taoyuan coast. A suite of instruments including pressure sensor, velocimetry, and video camera will be deployed along a line in the cross-shore direction to measure the wind, waves, currents, turbulence, and wave breaking over the reef. New types of high-frequency and high-resolution velocimeters called velocity profilers and current profiler will be used to obtain detailed flow structures. This project aims to understand how wave breaking and bottom roughness affecting the distributions of turbulent and wave stresses in shallow waters. This could be examined by comparing the measured quantities under breaking and non-breaking waves and on the reef flat and sandy bottom, respectively.