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

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30M. A. AzabFig. (9) Developmental land use Assessment along the coastal zoneof the Red Sea. Assessment as evaluated on a scale of 4 divisions(A throught D), D for the best sites and A for least sutiable sites.Mitigation Of Flash Flood HazardsThe spread of unplanned settlement and mis-management of the land and water resources inthe downstream areas along the coast will be responsible for the flood damages. The floodhazard risk depends upon exposure to floods, which has to be measured in terms of populationand land use activities (Chan and Parker1996) and the demands on natural resources exertedin either an unsustainable or sustainable manner (Woube 1999). In thinking about the floodproblem, the volume of fresh water lost in the sea needs to be taken into account. This wateris urgently needed for the development projects in the area. Flood also helps in recharginggroundwater aquifers. To avoid or alleviate flash flood damages and possibly to aid inexploitation of floodwater for recharging shallow aquifers the following preventive andcontrol measures should be considered. These measures can be summarized as follows:-1- Construction of successive incomplete rocky dams using the available locale materials atleast along the elongated main course of large wadis as Wadi Gemal, Wadi Lahmi and WadiErier (EI Shamy 1992).2- Construction of some loose boulder dams along the small tIibutaries of the main wadis todecrease the velocity of flood waters and increase their percolation into the wadi bed ( EIShamy 1992 ).3- Using the artificial recharge techniques may offer an important method for waterconservation to reduce the effect of evaporation in the area of study. Also, the onstruction ofsubsurface dams may create subsurface reservoirs (Hanson and Nilsson 1986).4- Decrease the elevation of the dual caring road and the main paved road to a lower level
FLOOD HAZARD BETWEE MARSA ALAM - RAS BAAS 31than the level of the crossing wadis floor in the narrow sectors to allow water flow directlyover these roads.COCLUSIOMorphometric parameters of most drainage basins in the area between Marsa Alam and RasBanas indicate low bifurcation ratio, and high values of drainage densities and frequenciesleading to the high possibilities for flash floods and low contribution for groundwaterrecharge. However, drainage basins of Wadi Samadi, Wadi Gemal, Wadi Um Abbas, WadiAbu Ghusun, Wadi Um Rimarim, Wadi Lahmi and Wadi Staiya are characterized by widedrainage channels and low density and thus their contribution to groundwater recharge isexpected to be high. Drainage basins of Wadi Samadi, Wadi Ghadir, Wadi Sharm Luli, WadiUrn Abbas and Wadi Khalilate EI Qibili are nearly circular in shape and thus reflect the mostfavourable conditions for the shortest runoff distance. The other drainage basins have lowelongation ratio and were classified as less dangerous basins. Probability of flash flooding isvery high for drainage basins of Wadi Radi, Wadi Ghadir, Wadi Ranga due to their highvalues of relief and ruggedness numbers. Wadi Gemal and Wadi Lahmi have the highestvalues of maximum runoff, which reflects the dangerous of their drainage basins. Under suchconditions, the construction of alternative barriers of boulder dams at the upstream parts of thedrainage basins will minimize flooding hazards and give more chance for groundwaterrecharge. The majority of wadis that display abnormal geomorphic features are related to thepresence of structural lines rather than any other surface or lithological features. To mitigatethe flash flood hazards and to increase the groundwater recharge, precautionary measuresneed to be taken into consideration at least at the high risk sites.REFERECESAshmawy, M. H., 1993: Assessment of flash flood potential of the Red Sea drainage basinsalong the Qena-Safaga highway, Eastern Desert, Egypt. ITC Journal 1994-2, pp.119-128, Netherlands.Ashmawy, M. H.; Swedan, A. H. and Abdel Fattah, T.,2000: Flash flood hazards ofdrainage basins of Sir" Peninsula, Egypt. Ann. Geol. Surv. Egypt, V. XXIII , pp.467-489.Ashmawy, M. H., 2001: Flash flood potential of Wadi Al Gemal catchment area southEastern Desert, Egypt. M. R C. Ain Shams Univ. Ser., V. 15, pp. 79-93.Ashmawy, M. H., 2002: Surface runoff potentiality and hazards of drainage basins alongthe eastern side of the Nile Valley between Asyut and Al-Minya, Egypt. Egypt. J. Geol., V.46/1 , pp. 283-300.Baker, V.R; Kochel, R.C.; Patton, P.C. and Pickup, G., 1983: Paleohydrologic analysis ofHolocene flood slack water sediments: Spec. Pub. Int. Assoc. Sed. V. 6, pp. 229-239.Baker, V.R and Pickup, G., 1987: Flood geomorphology of Katherine Gorge. NorthernTerritory, Australia. Geol. Soc. Am. Bull. V. 98, pp. 635-646.Ball, J., 1937: The water supply of Mersa Matruh: Survey and mines deposits. Paper No. 43,Cairo, 41 p.Boughton, W.C. and Renard, K.G., 1984: Flood frequency characteristics of some Arizonawatersheds. Water Rescuer. Bull. V. 20 (5), pp. 761-769.Chan, .W. and Parker, D., 1996: Response to dynamic flood hazard factors in PeninsularMalaysia: Geographical Journal, V.162(3), pp. 313-325.Chorley, RJ., 1971: The drainage basin as a fundamental geomorphic unit. In: Chorley, R.
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