Author(s): Qing Chang, So Kazama, Yoshiya Touge
Keywords: Urban hydrological model; SWMM; Scale analysis; Parameters;
Abstract: Urban catchments typically have high spatial variability and fast runoff processes which resulting in short response times. Thus distributed models are widely used in urban hydrology due to the capability to better capture the spatial heterogeneity. Selecting the proper spatial resolution (i.e., degree of aggregation) is not a trivial issue because this will affect the model output. However, a general consensus about the effect does not exist. This study investigated the impact of model input resolution on the outputs of detailed hydrodynamic models of an urban catchments in Sendai City of Japan. The aim is trying to quantify the impact of spatial resolution on model results and calibrated model parameters. Firstly a high resolution model was build up and calibrated. Based on this, a series of model was built via an upscale approach. The performances of these models were compared and afterward each model was calibrated independently. The parameterization and prediction capacities were discussed during and after the calibration. Finally, the runoff of an adjacent small catchment were modeled to analyze the model fidelity of performance and prediction at local scale. There were obvious scale effects across models due to the non-linearity nature of model structure. The peak flow tended to decrease with the upscale process while the total flow generally keep constant. Independent calibration had endowed all the models satisfied performance during the calibration period which indicated that calibration could completely compensate models’ scale effect. However, the deterioration during the validation suggested a result of missing certain spatial information.