干旱区生态环境知识资源中心

In arid and semiarid areas, the only surface and groundwater recharge source is the runoff generated through flash floods. Lack of hydrological data in such areas makes runoff estimation extremely complicated. Flash floods are considered catastrophic phenomena posing a major hazardous threat to cities, villages, and their infrastructures. The objective of this study is to assess the flash flood hazard and runoff inWadi Halyah and its sub-basins. Integration of morphometric parameters, geo-informatics, and hydrological models has been done to overcome the challenge of scarcity of data.

Advanced Spaceborne Thermal Emission and Reflection (ASTER) data was used to prepare a digital elevation model (DEM) with 30-m resolution, and geographical information system (GIS) was used in the evaluation of network, geometry, texture, and relief features of the morphometric parameters. Thirty-eight morphometric parameters were estimated and have been linked together for producing nine effective parameters for evaluation of the flash flood hazard in the study basin.

Flash flood hazard in Wadi Halyah and its sub-basins was identified and grouped into three classes depending on nine effective parameters directly influencing the flood prone areas. Calculated runoff volume of Wadi Halyah ranges from 26.7 x 10(6) to 111.4 x 10(6)m(3) with an inundation area of 15 and 27 km(2) at return periods of 5 and 100 years, respectively. Mathematical relationships among rainfall depth, runoff volume, infiltration losses, and rainfall excess demonstrate a strong directly proportional relationships with correlation coefficient of about 0.99.