A new assessment method on co-occurring mountain and plain floods based on copula functions

Abstract

Abstract Adjacent mountain area and plain area generally belong to the same climate zone, and a close hydraulic connection is also found between them. However, the flood controls in these two areas belong to different management departments. Flood occurring in these two areas can bring serious waterlog disasters, posing great threat to human lives and property. Previous studies mainly focused on the individual flood event in mountain or plain areas, while the research on the floods simultaneously occurring in both areas is insufficient. Hence, this study establishes a copula function-based assessment method to systematically analyze the characteristics of simultaneously-occurring floods in mountain and plain areas in Hangzhou City, thereby providing a basis for the collaborative management of floods in both areas. Results show that the proposed approach can give water level combinations in mountain and plain areas that are prone to co-occurring floods. Moreover, the water level in plain area is most likely to simultaneously appear with the water level in mountain areas under similar return periods, indicating that floods of equivalent level are likely to occur in plain areas when severe floods occur in mountain areas. This study provides a better understanding on the interplay of floods simultaneously occurring in mountain and plain areas, offering insights for coordinating the flood protection system in these two areas.