Geoinformatics application for assessing the morphometric characteristics' effect on hydrological response at watershed (case study of Wadi Qanunah, Saudi Arabia)

This study deals with the evaluation and inundation of flash flood hazard in the ungauged Wadi Qanunah basin depending on detail morphometric characteristics of Qanunah basin and its sub-basins. Data for this study were depending on ASTER data for digital elevation model (DEM) with 30-m resolution, topographic map (1: 50,000) and geological maps (1,250,000) which were verified during the fieldwork for evaluation of linear, areal, shape, and relief aspects of morphometric parameters. About 39 morphometric parameters were measured and calculated and interlinked to produce nine effective parameters to evaluate the flash flood hazard degree of the Wadi Qanunah basin. This study examined the physiographic features of the study basin with emphasis on their implication for hydrologic processes through the integration analysis between physiographic features and geographical information system (GIS) techniques. Wadi Qanunah basin was classified into 13 sub-basins, and according to their hazards degree, it is classified into three groups: basins of high hazard degree as for Wadi Qanunah sub-basin, basins of medium hazard degree as for Wadi Al Hafyan and Baydan 1 sub-basins, and basins of low hazard degree as for the rest of the sub-basins. Watershed Modeling System (WMS) and Hydrologic Engineering CenterHydrologic Modeling System software (HEC-HMS) were applied to generate the hydrograph of the two main sub-basins of Wadi Qanunah and Wadi Khatm Al Jurrah. The results of the model for maximum daily rainfall events of a total of 65, 79, 97, 110, and 123 mm with return periods of 5, 10, 25, 50, and 100 years, respectively. Total volume of discharge of Wadi Qanunah sub-basins ranges from 66 x 10(6) to 138 x 10(6) m(3), while for Wadi Khatm Al Jurrah sub-basin, it ranges from 11 x 10(6) to 24 x 10(6) m(3) at return periods from 5 to 10 years, respectively.