By using the high-speed camera and flow visualization approach,a physical model experiment was designed to study hydrodynamic parametes of overtopping flows on the crest.For the cases of sea dikes with and without fence panels,the measured layer thickness on the crest decrease exponentially in term of the distance along the crest,which accords with the results predicted by the empiric formula based on the shallow water equation.For the case of the fence panels,the experimental results show that the layer th...