Stream network and basin boundary extraction using GRASS GIS: EL-Barud basin, Safaga area, Red Sea coast, Egypt.

Abstract

The objective of this research is to explore the merits of the geographic information system (GIS) technology in a watershed characterization exercise in Safaga area on the Red Sea coast of Egypt, focusing on El-Barud watershed, the characteristics of which are among the significant factors contributing to the flash flood vulnerability resulting in extensive losses of life and properties. These characteristics are being quantified based on digital elevation model (DEM) tailored by exploiting the inter-contour areas information extracted from scanned topographic maps. Horizon, a FORTRAN program is used to extract the height information and to build the DEM at a grid spacing of 28.5 m. GRASS GIS system functionality for hydrological terrain analysis is then applied to the DEM and the most significant parameters that control the flow paths and other water borne compounds to the watershed outlet were extracted (i.e. basin boundary, stream-network, basin area, average slope, and wetness index). These watershed characteristics are then analyzed with the landuse map and the flash flood risk-prone areas are then identified. Finally, DEM and its derived hydrological products are evaluated. The study concludes that flash flood risk-prone populated area of about 7 km2 with its infrastructure and road networks as well as 45 km of the vital highway within the flood plain are frequently affected by flood hazards and mitigation practices to reduce flash flood risks need to be undertaken. The resulted watershed maps and hydrologic parameters can quickly and cost effectively help in such mitigation as well as to optimally utilize the flash flood water in a spatially explicit manner previously not available.