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Detailed morphometric characteristics of the catchment area were derived from the analysis of the 30 m resolution ASTER DEM (ASTER GDEM Validation Team 2011). ArcGIS-10, Arc-Hydro (ESRI Inc. 2012), and the correlated Topographic Parameterization Program (TOPAZ) of WMS-8.3 (2010) were used for the integrated analysis of the catchment involving the correlation and verification of topographic maps and DEM. These analyses were carried out to determine the spatially distributed time-area zones of the catchment to simulate the runoff hydrographs under different projected return periods for future storms over the long term. Various methods for channel network delineation and characterization were conducted, including DEM reconditioning, flow accumulation, flow direction, stream definition, sub-catchment definition, DEM slope, and others (Figures 4(a)4(f)). The raw DEM sinks were removed before being used in hydrological modeling (Mark 1984; Wise 2000). The flow direction was computed by calculating the steepest slope towards the surrounding cells. This flow direction was used to generate the flow accumulation map, which was used to delineate the stream networks to the outlets of the basin. Different threshold values proposed by Djokic et al. (1997) were examined to correct the generated flow lines with the actual network using the Landsat-8 and SPOT-5 images verification. The fourth order of the main wadi trunk was computed to attain the hydrologic analysis of the main basin (Figure 4(f)), while the morphometric parameters of the third order sub-basins were estimated to assess the flooding potentialities at this order level, since several small retardation dams could be proposed (Table 1 and Figure 4(g)).
Table 1

Characteristics of the main and third order sub-basins and their channel networks

 Sub-basin No. 1Sub-basin No. 2Sub-basin No. 3Sub-basin No. 4Sub-basin No. 5Main basin
Area (km215.02 4.07 3.43 2.81 0.97 36.70 
Length (km) 11.10 4.24 3.68 3.53 1.71 20.28 
Perimeter (km) 29.54 11.68 11.45 9.67 5.15 47.76 
Minimum elevation (m asl) 112 112 101 90 112 90 
Maximum elevation (m asl) 497 255 299 200 167 497 
Mean elevation (m) 212 147 150 100 123 159 
Height range (m) 385 143 198 110 55 407 
Slope (m/m) 0.15 0.10 0.12 0.04 0.05 0.11 
Average overland flow (m) 235 242 282 213 226 226 
North-facing aspect 0.53 0.66 0.54 0.39 0.64 0.51 
South-facing aspect 0.47 0.34 0.46 0.61 0.36 0.49 
Shape factor 3.96 2.48 2.95 2.67 2.02 2.81 
Elongation ratio 0.57 0.72 0.66 0.69 0.80 0.34 
Sinuosity factor 1.37 1.13 0.98 1.03 0.78 1.99 
Maximum flow distance (m) 11,104 4,236 3,684 3,226 1,703 20,313 
Maximum flow slope (m/m) 0.037 0.033 0.023 0.003 0.033 0.022 
Maximum stream length (m) 10,602 3,595 3,124 2,810 1,094 19,842 
Maximum stream slope (m/m) 0.026 0.009 0.023 0.003 0.017 0.016 
Distance from centroid to stream (m) 43.25 122.32 0.00 136.76 61.16 319.27 
Centroid to stream distance (m) 5,264 1,741 1,714 2,607 714 11,718 
Centroid to stream slope (m/m) 0.009 0.007 0.017 0.002 0.010 0.006 
 Sub-basin No. 1Sub-basin No. 2Sub-basin No. 3Sub-basin No. 4Sub-basin No. 5Main basin
Area (km215.02 4.07 3.43 2.81 0.97 36.70 
Length (km) 11.10 4.24 3.68 3.53 1.71 20.28 
Perimeter (km) 29.54 11.68 11.45 9.67 5.15 47.76 
Minimum elevation (m asl) 112 112 101 90 112 90 
Maximum elevation (m asl) 497 255 299 200 167 497 
Mean elevation (m) 212 147 150 100 123 159 
Height range (m) 385 143 198 110 55 407 
Slope (m/m) 0.15 0.10 0.12 0.04 0.05 0.11 
Average overland flow (m) 235 242 282 213 226 226 
North-facing aspect 0.53 0.66 0.54 0.39 0.64 0.51 
South-facing aspect 0.47 0.34 0.46 0.61 0.36 0.49 
Shape factor 3.96 2.48 2.95 2.67 2.02 2.81 
Elongation ratio 0.57 0.72 0.66 0.69 0.80 0.34 
Sinuosity factor 1.37 1.13 0.98 1.03 0.78 1.99 
Maximum flow distance (m) 11,104 4,236 3,684 3,226 1,703 20,313 
Maximum flow slope (m/m) 0.037 0.033 0.023 0.003 0.033 0.022 
Maximum stream length (m) 10,602 3,595 3,124 2,810 1,094 19,842 
Maximum stream slope (m/m) 0.026 0.009 0.023 0.003 0.017 0.016 
Distance from centroid to stream (m) 43.25 122.32 0.00 136.76 61.16 319.27 
Centroid to stream distance (m) 5,264 1,741 1,714 2,607 714 11,718 
Centroid to stream slope (m/m) 0.009 0.007 0.017 0.002 0.010 0.006 
Figure 4

Wadi Al-Burfi, Jazan area: (a) digital elevation model; (b) slope %; (c) flow direction; (d) flow accumulation; (e) sub-catchment boundaries; (f) stream network orders; (g) estimated morphometric parameters of the third order sub-basins.

Figure 4

Wadi Al-Burfi, Jazan area: (a) digital elevation model; (b) slope %; (c) flow direction; (d) flow accumulation; (e) sub-catchment boundaries; (f) stream network orders; (g) estimated morphometric parameters of the third order sub-basins.

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