Flash flooding is one of the periodic geohazards in the southern Red Sea Coast. However, their freshwaters are the main source of recharging alluvial and fractured aquifers. This paper presents hydrological and geomorphologic classification of Wadi El-Gemal, Wadi Umm El-Abas, Wadi Abu Ghuson and Wadi Lahmi, along the southeastern Red Sea Coast in Egypt. The main goal is to find a relationship of flash floods and groundwater recharge potentials. Satellite imageries and topographic data were analysed via remote sensing and GIS techniques. The main four valleys' orders range from six to seven. Wadi El-Gemal was the main focus of this study; it is characterized by high stream frequency, low stream density and coarse texture, reflecting influence of highly fractured Precambrian rocks. Most of the wadis have umbrella-shaped catchment areas, due to the influence of NW-SE Najd Fault System and late E-W strike-slip faults. The main wadis were divided into 45 sub-basins. 14 of the studied sub-basins flow into Wadi El-Gemal, 7 flow into Wadi Umm El-Abas, 10 are in Abu Ghuson, and rest of the basins flow into WadiLahmi. A conceptual model was used in this study, showing that most of the sub-basins have high flash flooding and low groundwater recharge potentials. However, only two sub-basins have low potential of flooding and high potential of groundwater recharge, whereas few sub-basins have moderate potential of groundwater recharge as well as flooding. For flash floods beneficiation and mitigation, construction of multifunctional embankment dams is imminent. F. Abdalla et al.

The source of the feldspar is found in the Late-Precambrian granitoid rocks of Al Madinah area, which covers about 2000 km 2 within a 44,000 km 2 area of the western part of Saudi Arabia. Petrographical and geochemical study shows that the granitic rocks have a considerable compositional range from quartz monzonite, quartz syenite, syenite, alkali granite to alkali feldspar granite. Mineralogical and petrographical results have revealed that Al Madinah granites are composed of quartz, K-feldspar, Na-plagioclase and muscovite. Geochemical data for the feldspar samples show average SiO

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