Abstract:
This study focuses on flood event based hydrological modeling using HEC-HMS and geographic information system (GIS) on sub-catchments of Neelum and Jhelum rivers of Muzaffarabad, District Pakistan. The sub-catchments of Neelum and Jhelum, in Muzaffarabad, are the domain of the study because it is a region subject to frequent occurrences of severe flash flooding. Modeling was done on extremely high rainfall event of July 2002 for calibration and on July-August 2010 event for validation purpose. Soil conservation services (SCS) and Green Ampt loss methods were used to simulate the loss component of the model. Parameters were estimated for SCS-CN and Green Ampt loss methods using HEC-Geo HMS model. Digital elevation model (DEM) was the main input for basin processing of the catchments. Land Cover maps obtained from images of Landsat 4-5 and soil maps were merged together to obtain curve number (CN) of each sub basins while parameters for Green and Ampt i.e loss method were obtained from Green and Ampt lookup table. Lag time, basin lag, curve number and initial abstraction parameters were calculated using the above methods. Correlation analysis between observed and simulated hydrograph showed that SCS Curve Number had significant correlation (r = 0.7) while Green Ampt which had low correlation (r = 0.58) on sub basin 1. Results found Nash value of 0.98 using SCS curve number and 0.97 using Green and Ampt loss method in calibrated events for Neelum River sub catchment. Parameters estimated through GIS and HEC-Geo HMS tools enhanced model capabilities to simulate stream discharge that was in close agreement with observed stream flow. Peak discharge rates by incorporating land use, soil type and hydrological conditions show efficient loss methods for flood forecasting and managements strategies
