Urban flooding response to rainstorm scenarios under different return period types

• A new urban rainstorm pattern design method. • Realization of design value of characteristic rainstorm elements in multivariate environment. • The effects of various return period definitions on urban flooding results. Urban flooding research cannot be overemphasized due to its environmental, economic and societal concern. Research on the response of urban flooding under different rainstorm scenarios would be conducive to the design of drainage projects, and helps the government department to master the waterlogging process in advance. Thus, this paper introduces a new rainstorm pattern designing method using Copula theory, Most-Likely design realization method and Monte Carlo simulation based on the rainfall data in a Chinese megacity, Zhengzhou. Furthermore, a coupled one-dimensional and two-dimensional hydrodynamic model, MIKE FLOOD, was used to determine the urban flooding response to various rainstorm scenarios. The results show that more than 75 percent of waterlogging disasters in Zhengzhou city were caused by short duration rainstorms within 3 hours, and the one-hour single-peak rainstorm process plays a main role. The rainstorm volume (RV) under Kendall return period type decreased significantly compared with the radical “Or” return period. And the RV under survival Kendall return period type was improved compared to the conservative “And” return period. Moreover, the rainstorm scenario corresponding to “Or” return period brought about the most serious waterlogging disaster, with the peak inundation volume of 1.8 × 10 5 m³ and the maximum water depth of 1.86 m.