Subareal wave pressures, layer thicknesses, run-up and run-down velocity on sea walls

Abstract

Wave pressures, layer thickness, run-up and run-down velocities were measured on the splash/subareal zone (the part of the seawall which is partially in water during run up and partially in the air during run down) of plane seawalls for a wide range of hydrodynamic parameters and seawall slopes. The complete wave breaking range (spilling, plunging, collapsing and surging) is covered in the study. The maximum wave pressure in the subareal region can be as high as 1.2 times the static pressure due to water column equal to the incident wave height. The maximum wave pressure at any point is higher than the water pressure induced by the layer thickness due to the dynamic contribution of the flowing water on the seawall. The maximum run up and run down velocity can be as high as 25 times the maximum horizontal water particle velocity in deep water. The run-down velocity is found to be higher than the run-up velocity for the same input condition. Using the measured data, empirical formulae are proposed to predict the subareal wave pressures, layer thicknesses, and run-up and run-down velocities. The proposed formulae incorporate the surf similarity parameter and relative elevation of the location on the subareal region of the seawall. The empirical equations are simple, reliable and hence can be used for the optimal design of plane seawalls.