Risk of hydrological failure under the compound effects of instant flow and precipitation peaks under climate change: A case study of Mountain Island Dam, North Carolina

Abstract

The risk of flooding as a result of infrastructure failures among aging dams in the United States continues to increase dramatically, which lead to the severe consequences in socio-economic and environmental terms. Environmental impacts regarding the failure of hydrological facilities, including the loss of sustainable habitats and clean water previously provided by reservoir, have raised concerns. In this study, the potential risks to hydrological infrastructure within the context of the 100-year joint probability of maximum rainfall and peak water stage were examined over the Mountain Island Dam (North Carolina, USA) for the period of 1950–2099. We found that nearly 92% of annual maximum extreme rainfall events were closely related to the passage of hurricanes over the dam’s watershed over the 25 years of the validation period. The results show that the projected annual maximum precipitation is likely to intensify under the RCP8.5 climate scenario and the frequency of the annual precipitation maxima exceeding 100 mm/day is projected to increase in the future. Noticeably, it is found that even weaker storm events can contribute a significant amount of rainfall at inland locations. The probability of occurrence of a hurricane like Gustav is higher than that of a 100-year storm rainfall event under the RCP8.5 climate change scenario, this type of storm rainfall will more likely occur near the Mountain Island Dam in the future. Inspectors should focus more on observing water level fluctuation and rainfall volume variation at station two under the same rainstorm - water level situations, because it is more sensitive to the once-in-a-century co-occurrence event than other stations. A HEC-RAS (The Hydrologic Engineering Center (HEC) developed the River Analysis System (RAS) to aid hydraulic engineers in channel flow analysis and floodplain determination) simulation demonstrated that the occurrence probability of hurricane Gustav induced rainfall is more than that of 100-year rainfall events and this type of storm rainfall would highly likely occur near the Mountain Island Dam again under the future warming conditions by the conditional prediction of Copula function. Insights gained suggest that it is critical to evaluate the risk of dam failures regarding either extreme weather conditions or potential environmental concerns under the climate change scenarios, especially where human lives are threatened.