| Abstract
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Large Format Camera stereo photographs and a Landsat Thematic Mapper image were used to map lineaments, drainage lines, and lithologic units in an area covering approximately 57,000 km2 in the basement complex of the Red Sea Hills of eastern Sudan. Detailed quantitative and qualitative analyses of geomorphologic, structural, and spectral features were conducted of a smaller sub-area (3,500 km enclosing Khor Quwab and Khor Ashat, southwest of Suakin. The aim of the study is to examine the influence of basement fractures on drainage and groundwater flow. The Landsat image was used to extract geologic information on an area where no detailed geologic maps exist. Digital enhancement techniques, such as contrast stretching, filtering, and multispectral enhancement, were applied to emphasize distinctive lithologic units, and structural patterns. Geomorphologic analysis consisted of measuring and interrelating basin parameters, such as channel order, stream numbers, stream lengths, and basin areas. The results indicate that: (1) the drainage network is generally not randomly developed; (2) drainage basin development has reached a mature stage, and (3) both drainage basin configuration and drainage network, are controlled by tectonic features. The main structural trends of the basement complex correlate with drainage patterns, topographic features, lithology and the present-day stress field resulting from the opening of the Red Sea. These data form the basis of the model which permits the identification of open vertical fractures that may serve as storage zones, collectors or transmitters of groundwater, and represent potential links between surface and subsurface water. Results of the geomorphic, structural, and digital image analysis were correlated using GRASS, a Geographic Information System, in order to assess their potential role in controlling groundwater flow and storage. Based on these correlations a model is proposed of groundwater flow in the fractured bedrock for the Quwab-Ashat region.
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