flood hazard betwee marsa alam - ras ba as, red sea, egypt abstract ...

18M. A. AzabBaker and Pickup (1987), Cunnane (1987), Klemes (1987), Tasker (1987), Patton (1988) andSummerfield (1991). Moreover, studies in fluvial geomorphology and morphometry of someflood vulnerable areas of Egypt such as Sinai and the Eastern Desert and have receivedparticulars consideration by some workers (e.g. Mobarek et al. 1981; EI Kassas and ElRakaiby 1983; Salem 1985; El Shamy 1985, Schick and Lekach 1987; Saleh 1989 a, b, c; ElRakaiby 1989; EI Etr and Ashmawy 1993; Ashmawy 1993; Yahia et al. 1999 a, b; EI-Etr etal. 1999; Ashmawy et al. 2000; Ashmawy 2001,2002 and Kamh 2002).The study area is located in the central Eastern Desert of Egypt and lies entirely within thecatchment area of the Red Sea. It is bounded from the east by the Red Sea and from the westby the River Nile-Red Sea water divide, and is limited by maximum latitudes 24° and 25° N(Fig. 1). It is of elongated and covers an area of about 6000 km2.Geomorphological studies may give information about the areas affected by flooding.Studying the morphometric parameters of drainage basins is very important for determinationof the intensity of floods, and provides suitable solutions for avoiding or reducing as much aspossible, hazards that occur, in addition to increasing groundwater recharge. The study of thehydro-geochemical characters of groundwater in Wadi EI-Gemal basin (at the middle part ofthe study area) is important for domestic, livestock and irrigation uses. Beside deciphering thedifferent landforms and the drainage courses and their basins, this study helps to define thelocations and distribution of the Plio-Quaternary fans of probably great importance to thegroundwater recharge.Methods Of StudyQualitative and quantitative geomorphic analyses of the drainage basins in the area betweenMarsa Alam and Ras Banas were measured and analyzed for flash flood (Fig. 1).These parameters give a better understanding for surface water potentialities in the definedhydrographic basins. Drainage networks of each drainage basin were delineated from photomosaic(1 :50,000), topographic maps (24 maps at scale 1 :50,000) and landsat images ofscale 1:50.000, as well as, field observations. Twenty-three drainage basins were defined andmapped.The geomorphological parameters of each basin were defined in terms of stream order,bifurcation ratio (Horton 1945 and Strahler 1952), basin shape (Miller 1953 and Schumm1956), sinuosity (Mueller 1968), relief ratio (Schumm 1956.) and ruggedness number (Melton1957). The rainfall and surface runoff were defined according to the equation given by Ball(1937).Topography And GeomorphologyThe study area comprises essentially high and rugged mountains, built up of a seriesmountain our range, more or less coherently trending parallel to the coast and interrupted by anumber of detached masses and peaks (Fig. 2). The high peaks are concentrated in thesouthwestern corner where they rise to elevations up to 1975m (Gaba1 Hamata). The RiverNile-Red Sea water divide runs over the high peaks of the Red Sea Mountains with anaverage elevation of 650m. A large number of wadis initiate from the mountainous terraindissecting the area and run toward the Red Sea following the general eastward slope. They aremostly oriented E-W, WNW-ENE, NNW-SSE and NE-NW. The main wadis are veryimportant sutable areas for extending net of roads crossing the area and as the main arteriesfor groundwater. Slope gradient is mostly steep in the upper reaches of drainageways andtends to be gentle to the east.