Using remote sensing and GIS techniques for identifying influence of seasonal flashfloods on El-Qaa plain, Egypt

Abstract

El-Qaa plain lies in the southern part of Sinai Peninsula extending along the Gulf of Suez. It occupies an area of about 3300 km2. El-Qaa plain is suffering from seasonal flashflood that can roll boulders, tear out trees, destroy local people buildings, and scour out new channels. Flashfloods are among the most frequent and costly natural disasters in terms of human hardship and economic loss. Terrain units of ElQaa plain were interpreted by draping satellite ETM+ image over Digital Terrain Model (DTM).These units could be categorized into sand sheet, outwash plain, inter-ridged sand flat, wadi bottom, wadi outlet, dry valley, delta,dry &wet sabkhas, ridge, rocky hill, cuesta, peniplain, rockoutcrop, footslope, bajada & alluvial fans, inclined lime stone, marine spits & heads and water bodies. On the other hand soils of ElQaa plain were classified into the following sub groups: Calcic Haplosalids, Gypsic Haplosalids, Lithic Haplocalcids, Lithic Torripsamments, Typic Aquisalids, Typic Haplodurids, Typic Torripsamments, and Typic Haplocalcids. Arc Hydro Model was used with the aid of DTM for deriving slope, flow direction, basins, flow length and flow accumulation. These derivations influence directly the flashflood behavior. Universal Soil Loss Equation (RUSLE) was used to estimate soil loss in ElQaa plain using GIS spatial analyses. The minimum mean soil loss belonging to water erosion was determined by 1.23 ton\hectare\year, meanwhile the maximum one was estimated by 5.08 ton\hectare\year. Alternative management and potential cropping system was suggested to adequate conservation measures in farm planning system of ElQaa plain. These measures could be grouped under 1-Selection of appropriate landuse. 2-Maintaining organic matter. 3-Reducing tillage. 4-Using zero tillage or direct seeding. 5-Growing forages and using crop rotations.