A novel method for calculating distributed water depth and flow velocity of stormwater runoff during the heavy rainfall events

Abstract

• Traditional calculation method of runoff depth and flow velocity is inefficient. • The proposed novel method fully couples hydrological model and hydrodynamic model. • Runoff depth can be simplified as a power function of the catchment area. This work presents a novel method to calculate the distributed water depth and flow velocity of heavy rainfall-induced stormwater runoff. Although the shallow water equations or other numerical models are often employed to deal with the calculation of distributed water depth and flow velocity of runoff, it still suffers from low computational efficiency due to low convergence. This restricts its applicability to early warning of geological disasters (floods and debris flows). The novel method proposed in this work fully integrates the conceptual hydrological model and hydrodynamic model and gives full play to the advantages of both. In the novel method, based on the two equivalence relations between the hydrological model and the hydrodynamic model, i.e., the discharge at the boundary of the catchment and the total water storage in the catchment calculated by the two models should be equal at all times, a governing equation in Ordinary Differential Equation (ODE) form of stormwater runoff simulation is obtained, named distributed runoff model (DRM). The effectiveness and practicality of the DRM have been verified by three validation systems. Results indicate that the DRM can calculate distributed water depth and flow velocity of heavy rainfall-induced stormwater runoff with a low degree of difficulty and a high degree of accuracy and efficiency.