Characterizing and understanding the effects of spatial resolution in urban hydrologic simulations

Abstract

Model subdivision is used to capture spatial heterogeneity in input parameters and it is well-established that spatial resolution affects model output. Although previous research has observed scale effects in urban hydrology, there is no general consensus about it or the underlying mechanism(s). The objective of this study was to investigate the effects of spatial resolution on model predictions in an urban catchment, and to understand the mechanism(s) responsible for the scale effect. The study area is the Faneuil Brook sub-basin of the lower Charles River watershed in Boston. The general approach used in this study is to develop models at various spatial resolutions (from 4 to 616 subcatchments), perform simulations and compare the predictions of total outflow volume and peak flow. Models were developed based on actual drainage networks, and artificial ones generated based on a fractal algorithm using the program Artificial Network Generator (ANGel), which was written as part of this research. Simulations were performed using the EPA Storm Water Management Model (SWMM) and model output was compared for 90 different storms.