Rainfall- runoff modeling using hec-hms/ Siti Munirah Ismail

The changes of natural hydrology characteristic due to the replacement of natural
vegetation to a high percentage of impervious surfaces in the watershed will effect to the
volume of runoff in receiving water. It is due to the increasing of surface runoff and flow
velocities which will cause to decrease in flow travel time. This phenomenon has
alleviate problems regarding the local runoff impacts on receiving water flow and lead to
increase in flood peak. In Malaysia, flooding is one of the natural hazards that affect the
communities and have caused damages worth of million every year. For more than thirty
years, computer models have been used as an essential tool for flood analysis. This
report depicts a hydrologic engineering study carried out at Sg. Junjung, Penang,
Malaysia for rainfall runoff modelling using HEC-HMS. The Hydrologic Modeling
System is designed to simulate the rainfall-runoff processes of dendritic watershed
systems. HEC-HMS model was used to predict design flow for major system (ARI 50
and ARI 100 years). The data collected were used to develop flow rating curve and to
derive historical and predicted flood hydrograph. The historical flood hydrograph for the
20th
-21st October 2005 was used to calibrate with the predicted flood hydrograph (HECHMS model). The calibrated model was validated with historical flood hydrograph on
storm event 15th
-17th July 2005. Hydrographs produced by this study can be used
directly or in conjunction with other software for studies of water availability, urban
drainage, flow forecasting, future urbanization impact, weir design, flood damage
reduction, floodplain regulation, wetlands hydrology, and systems operation.