Based on the results of full-scale flume tests, characteristics of combined wave and surge overtopping at relative freeboard were analyzed and classified. According to this classification, discharges of combined wave and surge overtopping measured from the full-scale flume test was fitted with the Weibull distribution, and distributions of individual overtopping volumes and instantaneous overtopping discharge were studied respectively. New empirical equations have been proposed to estimation the distribution of individual overtopping volumes and instantaneous overtopping discharge, which improved the estimation accuracy of them compared with the existing methods.