Impact of modeling methods on urban flood processes at community scale

Constructing rainfall-runoff models at the community scale involves challenges due to varying data availability and the potential generalization of critical microtopographical features or the use of different modeling approaches. It is crucial and urgent that the differences among various modeling methods are understood under different external boundary conditions. This work examines the synergistic relationship between these modeling approaches and the LID facilities within communities, while also considering the impact of key microtopographical features on runoff processes. The study finds that: (1) Full hydrodynamic models exhibit significant biases at lower cumulative rainfall levels, which diminish as cumulative rainfall increases. Simulation errors reduce notably after accounting for downspouts, yet considering LID facilities cause overall increase in errors. (2) LID facilities enhance runoff control at lower cumulative rainfall levels but reduce it at higher cumulative rainfall levels. (3) Directly connecting downspouts to rain gardens significantly reduces inundated area, volume, and peak flow, enhancing the regulatory efficiency of LID facilities. (4) Surface and subsurface runoff processes at the community scale show limited sensitivity to changes in rain garden overflow well heights during lower cumulative rainfall levels. This study offers insights into selecting appropriate community-scale rainfall-runoff modeling methods under various boundary conditions.