Flash Flood Management: A Case Study of Dera Ghazi Khan City

Abstract

Pakistan is one of the south Asian countries that are affected frequently by flash floods. Hill-torrent leaning flash flood of 2012 has broken all the former records in Dera Ghazi Khan (D.G. Khan) by means of damages and discharge. For the assessment of flash flood disaster, PGIS (Participatory Geographic Information System) technique, developed for understanding of local community perception, has been used in this study by surveying 1273 households in the flood affected areas. With the identified risk elements, analysis was performed using depth damage relationship. As a mitigation strategy, the study identifies suitable location for dam construction with quantitative analysis resulting in capacity determination of the designed dams. The developed methodology also incorporates the designing of downslope water conveyance system in Storm Water Management Model’s (SWMM) environment. The efficiency of the dams was analyzed using SWMM model’s runoff and transport module by integrating meteorological and topographic factors with the utilization of Curve Number (CN) method for runoff generation and modeling. The result shows an increasing trend in physical vulnerability and risk with the increase in flood inundation level and population density and with the decrease in the distance from the source. For flash flood management study proposed 2 suitable dam sites with sufficient collective designed capacity of approximately 27 million cubic meters to accumulate the generated peak runoff. Number of channels designed results in systematic waterways to flow from the dam site to the outlet point (D.G. Khan Canal). The findings may be useful for relief programs and precaution measures for the development of better coping mechanism for flash flood management of the area.