Runoff Modeling of the Saugatucket River: An Application of HEC-HMS Software

Abstract

The U.S. Army Corps of Engineers had revised its HEC-1 software. The new version is HEC-HMS (Hydrological Modeling System). This versatile software retains all computational and analysis capabilities of the old version with additional features, which includes CAD (Computer Aided Design) like modeling techniques (icon and dialogue box driven). The main objective of this project is to model flow response from a rainfall event in the Saugatucket River. Through model selection process, HEC-HMS was selected as the appropriate software for implementation. The modeling technique used here is different from standard professional practice in the model calibration and validation. This project utilizes actual observed flow data for model calibration and validation. Standard professional practice depends highly on synthetic methods for model calibration. Model validation is often ignored. Features of HEC-HMS allow for the application of observed data for model calibration. In implementation, an interesting discovery was made. The percent impervious for some subbasin areas in the Saugatucket watershed were dependent on leaf interception. This is evident in small storms, which leaf interception has major influences. In using the observed data, the Muskingum coefficients "K" and "x" cannot be derived directly due to contribution from subbasin areas. A technique was developed to solve this problem, which includes implementing the convex routing method prior to deriving Muskingum coefficients "K" and "x". At the conclusion, the summer model is validated by an independent wet weather data set.