Hydro-Geomorphic Characteristics of Gash and Nyala seasonal valleys were examined to portray their hydrological behavior which is proficiently potential to sustain water harvesting programs for rural development in semi arid Sudan. Data sources were results of field work carried out by TNO-DGV Institute of Applied Geosciences-Netherlands and National Water Corporation of Sudan, Gash’s satellite image provided by Geological Research Authority of Sudan, relevant research done there and GIS analysis of recent satellite imageries of the two valleys. The research adopted descriptive, analytical and derivational approaches. Results depicted that, geomorphological characteristics of Gash and Nyala valleys are almost identical and although they differ in geographic locations, they are both influenced by the Intertropical convergence Zone (ITCZ) and Indian Ocean monsoons which determine the initiation of their annual flooding. They are of mountainous sources, flashy with huge annual discharge and are typically similar in their hydrological behavior. They endanger Kassala and Nyala regional towns and their geographic neighborhood to floods disasters; however the two valleys are potential to contribute into sustainable rural community development by adoption of appropriate water harvesting programs. The research recommended improvement of hydrological recording and estimates, geomorphic controls and precipitation estimate to enhance water harvesting programs and reducing vulnerability of flood disasters.