Comparative study of the drainage basin morphometry extracted from topographic maps and SRTM DEMs: an example from Ghadir watershed, Eastern Desert, Egypt

Abstract

The drainage network of Wadi Ghadir watershed, southeastern Desert, Egyptwas extracted from topographic maps (1:50. 000), and from the 30 m digitalelevation data (DEM) of the Shuttle Radar Topography Mapping Mission(SRTM). Four topographic sheets were digitized and used for extraction.Archydro function in ArcGIS 10x was utilized for network extraction and formorphometric analysis. Networks derived from topographic sheets and DEMwere considerably coincident. Different morphometric parameters from bothsources were evaluated to examine the accuracy of DEM for hydrologicapplications. Results clarified 6th order streams for both drainage networks withmoderate to high drainage density (D) of 2.51 km.km2 (topographic) and 2.54km.km2 (DEM) reflecting that W. Ghadir drainage basin is impermeable withconsiderable surface runoff. DEM showed higher stream frequency (F) of 4.49than those derived from topographic maps (4.38). Calculated bifurcation ratio(Rb) of streams derived from topographic sheets reached about 3.47 and about4.60 for those derived from DEM. DEM-derived morphometric parametersprovided good and satisfactory information about the catchment characteristicsand revealed accurate watershed delineation confirming high potential ofsurface runoff of the W. Ghadir drainage basin. Finally, SRTM DEM provedadvantageous over the topographic sheets for drainage delineation and basinmorphometry for hydrologic analysis underpinned with the finer spatialresolution and the vertical accuracy.