Calibration of Distributed Rainfall-Runoff Model in Hamilton County, Ohio

Abstract

Appropriate parameter estimation for the assessment of green infrastructure alternatives in combined sewer systems (CSS) is becoming more important in rainfall-runoff modeling. This chapter studies the calibration of eleven individual storm events in a distributed rainfall-runoff model in SWMM5 for the assessment of green infrastructure in a combined sewer system. High detail rainfall and flow measurements were used. Parameters that represent the area in the model were assumed fixed in this study.The model independent parameter estimation (PEST) method was used for both parameter estimation and sensitivity analysis. A base flow that includes dry weather flow (DWF) and ground water infiltration (GWI) improved the performance of the simulated hydrographs in the CSS. This study shows that there was not unique set of parameters values that can be used for simulation of the single storm events selected. There was significant variation of the calibration parameter values. Roughness and depth storage in the impervious surfaces were the more sensitive parameters within the calibration process. The sensitivity analysis identified high non-linearity due to high correlation between parameters. There is a systematic bias in the model that needs further research.