Effect of Spatial Resolution in Modeling Stormwater Runoff for an Urban Block

This study assesses the role of spatial resolution in hydrologic and hydraulic models by means of two models developed at different resolutions for an urban block using the U.S. Environmental Protection Agency’s stormwater management model (SWMM). The first is a high-resolution model, in which distinct elements are represented as individual hydrologic response units (HRU). The second is a low-resolution model, in which the entire block is represented as a single HRU. Flow observations during five storms were used to calibrate the models, while a separate set of six storms was used to assess their performance. The high-resolution model was found to systematically underestimate peak flows, whereas the performance of the low-resolution model was found to be dependent on the type of storm. Overall, the two models displayed similar accuracy according to most metrics, thus justifying modeling at high resolution only in those cases where a detailed representation is necessary.