Investigation of the drainage loss effects with a street view based drainage calculation method in hydrodynamic modelling of pluvial floods in urbanized area

Drainage loss effects are crucial for flash flood modelling induced by torrential rains in urbanized environment. This paper proposes a novel approach for incorporating drainage loss effects into two-dimensional hydrodynamic overland flow simulations with the open source databases offered by geographical information providers. Street inlet locations within the road network are determined using street view images based on feature points extracted throughout automatic navigation along the roads in the panoramas, where the runoff of the surface flood flow is determined by the drainage network's capacity. By implementing the proposed data acquisition and drainage loss calculation method into the 2D overflow model HiPIMS as an alternative to the often-unrealizable physically based method or to the overly simplistic rainfall reduction method, the flood modelling results are validated against field observations during severe flood events in an intensely urbanized area to demonstrate the feasibility and effectiveness of the newly proposed method. In comparison to other simulation scenarios without drainage loss effects or with those considered by the rainfall reduction method, the drainage loss effects induced by the newly proposed method are analyzed for both the spatially lumped and distributed urban flood patterns. While the drainage effects are more essential after the rainfall peak hours for the flood extent as spatially lumped results, the low-lying area with dense building complexes are found to benefit more from the drainage effects in a spatially distributed way. Variations of the speed and direction of flood flows caused by the drainage effects at inlets are observed to depend on the surrounding environment. Competitions between the drainage effects and the gravity effects induced by topographical features are revealed with street-level evaluations of the flood modeling results using high-resolution hydrodynamic modeling in conjunction with the proposed drainage calculation approach.