Abstract

Assessing the overtopping risk has become a necessity in face of ever-changing, extreme weather conditions. This study proposed a novel probabilistic framework to evaluate the overtopping risk of a case embankment dam equipped with both gated Ogee spillway and erodible auxiliary spillway i.e., “fuse plug”. The reservoir routing equations have been adapted to account for the existence and subsequent destruction of the fuse plug. The characteristics of rainfall events and the catchment hydrological parameters were considered as random variables. Furthermore, an innovative random rainfall generator based on copula process was introduced to produce stochastic rain hyetographs. Considering the reservoir at Ogee crest level and normal water level, the probabilities of overtopping from the fuse plug were 9.2% and 10.6% in case of a 1000-year-daily rainfall, respectively. For these normal water levels, the probabilities of overtopping from dam crest are 0.52% and 0.55%, indicating an approximately identical risk. In addition, the uncertainty in the ratio of rain event to daily rain event, curve number, rainfall depth, and concentration time (in sequence) result in significant variations of reservoir water level. The variability in rainfall hyetograph influences the reservoir water height insignificantly. Regarding reservoir routing, the fuse plug destruction, significantly decreases the attenuation of peak discharge.