Abstract:
Floods are among the most devastating natural hazards in the world causing huge losses of lives and infrastructure. Floods can be predicted but it‟s very hard to make its effects less severe. Flood can destroy human life, destroy the homes, infrastructure, buildings, and everything that comes in its way. Poor prediction of the flood can lead to a widespread damages. Pakistan is an underdeveloped country that has seen an increasing number of floods in the last couple of decades. Lai Nullah is situated in Rawalpindi district of Pakistan, twin city of capital Islamabad. It has basin area of 235 km2. It has a history of flood after every three years. In 2001 there was a huge flood in Nullah which claims 74 people and affected 400,000 people, 742 cattle head perished, 1,087 houses completely damaged and 2,448 partially damaged, inflicting a capital loss of US$ 250 million to infrastructure, government and private property. In this study, the flood of 2001 has been simulated using a technique called 1D-2D coupling. Two software have been used for this study; one is BASEMENT which calculates the flood extends velocity, water depth and water surface elevation. The other software is Surface-Water Modeling System (SMS) and Fudaa-Prepro, which are used for visualization of results. The results have been verified with an already carried out study by Japan International Cooperation Agency (JICA, 2003) and fully 2D model (Umer, M. 2015). The 5.91 km2 extent has been calculated which is very close to the 6.01 Km2 calculated by JICA with a water depth of 5-6 meters in a low lying area called Naya Mohalla near Liaquat Road and Gawalmandi Bridge. Simulated results are in close agreement with the JICA results as far as the floodplain is concerned but deviations are observed over the main channel due to the non-availability of reliable data for the cross sections. In the current study, the input hydrological data has been only taken at Katarian Bridge. It is suggested that if the hydrological data may be taken for the main Lai Nullah along with all of its tributaries like Niki Lai and Dhok Hassu Nullah which join the Lai below the Khabane-Sir-syed bridge and Peerwadi bridge respectively, the results may be better.
