Interim guidance for prediction of wave run-up on beaches

Abstract

A method of predicting wind wave run-up (for any desired quantile or statistic value) on smooth linear mild slopes has been presented. The method is based on a re-analysis of an extensive laboratory measurement run-up data base of Mase [(1989), Random wave run-up height on gentle slopes. J. WatWay, Port, Coastal, Ocean Engng Div., ASCE 115, 649–661] and Mase and Iwagaki [(1984), Run-up of random waves on gentle slopes. Proceedings of the 19th Coastal Engineering Conference, ASCE, pp. 593–609]. The predictive run-up measurement equation is based on a modified dimensionless form of the Hunt [(1959), Design of seawalls and breakwaters. Proc. J. WatWay Harbour Div., ASCE, 85, 123–152] formula with a linear intercept term (which appears to be due to mild slope wave set-up). Values of the slope coefficient in the run-up predictive equation are based on the Rayleigh probability distribution in accordance with findings from the present re-analysis of the Mase data set. Run-up prediction for a given quantile or statistic value is then found utilizing the slope coefficient based on Rayleigh theory combined with the predictive linear equation found herein for the average run-up height R mean in a stationary wave train. In the case of rough slopes and permeable beaches, it is obvious that the true run-up would be reduced from the predicted values of run-up given by the smooth slope method provided herein. At present the extent of such reduction is a matter of speculation. As an interim measure, it is recommended that conservative design practice be followed by using the run-up values predicted via the method given herein unless sufficient justification for run-up reduction based on laboratory or field findings can be provided.