Abstract
The flood mechanism and inundation behavior of a watershed in the Pothowar (semi-hilly) region of Pakistan was investigated by computer modeling. The Lai Stream Basin has an area of 235 km(2) and is located in northern Pakistan. Lai is the main stream passing through the city of Rawalpindi and has a history of flood damage of almost once every three years. The flood of 2001 was the largest among recorded events, claiming 74 human lives, affecting 400,000 people and inflicting a capital loss of US$ 250 million. Mike 11 software was used to develop a valid rainfall-runoff model for the basin using refined rainfall data and available cross-section data, and a simulation was performed to confirm the reproduction of the 2001 flood event. Thereafter, the model was slightly modified to simulate standard flood discharges for various return periods. Flood inundation was then assessed by generating flood maps of the area for various future scenarios using a geographic information system interface. From the results of this study, recommendations regarding the orderly arrangement of gauged data, increasing in the number of rainfall gauging stations, installing automatic water-level gauging stations, establishing a proper flood warning code, establishing an efficient flood forecasting and warning system, regular channel desilting activities, updating the rating curve at a reference point and generating a flood hazard map were made to mitigate the flash flood hazard in the urban/inhabited Pothowar region of Pakistan.