Groundwater Sapping Process and Runoff of Old River Systems in the Great Sand Sea and the Gilf El Kebir Plateau, Western Desert of Egypt

The present work delineates two main patterns of drainage in the Western Province of the Western Desert. The first pattern was formed by runoff of old river systems and has a restricted geographic distribution on the top surface and slopes of the scarps of the Gilf El Kebir Plateau but it is generally low, intermittent, having a limited duration in the westernmost part of the Great Sand Sea along the Egyptian Libyan borders. The second pattern was and still formed by groundwater sapping process which has a widespread distribution along the slopes of the Gilf El Kebir Plateau, the Nubia Sandstone hills distributed in the Dakhla Basin and the slopes of the widely distributed longitudinal Nubia Sandstone ridges in the Great Sand Sea between the Gilf El Kebir in the south and Siwa Oasis in the north. The phenomenon of lateral flowing of groundwater and its emergence as seeps at the edges of the scarps was and still today the main erosion process that produces major landforms with unique characteristics in the Great Sand Sea. It causes disintegration and breakdown of the Nubia Sandstone bedrock and erosion of the sandstone from the slopes, causing the slopes to be undermined and undergo mass wasting. It is also the predominant mechanism of the growth of the amphitheater headed valleys, and the flat topped surfaces of the upraised plateaus as well as the exploitation of joints and fractures in the Nubia Sandstone bedrock. In addition it is responsible of formation of different types of alcoves in headwalls, spring sites and seepage zones in many valley flanks. Moreover, vast areas of the Nubia Sandstone bedrock of the flat topped plateaus, flat tracks and depressions are found to be eroded, well exposed, clean, and covered by silica debris as a result of intense erosion by the groundwater seepage. Khaled Abdel-Kader Ouda "Groundwater Sapping Process and Runoff of Old River Systems in the Great Sand Sea and the Gilf El Kebir Plateau, Western Desert of Egypt" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-7 | Issue-5 , October 2023, URL: https://www.ijtsrd.com/papers/ijtsrd59885.pdf Paper Url: https://www.ijtsrd.com/other-scientific-research-area/geology/59885/groundwater-sapping-process-and-runoff-of-old-river-systems-in-the-great-sand-sea-and-the-gilf-el-kebir-plateau-western-desert-of-egypt/khaled-abdelkader-ouda