The construction of the Grand Ethiopian Renaissance Dam (GERD) will have positive and negative impacts on the people living downstream. Among possible impacts is the probability of flooding of human settlements along the Blue Nile. Reduction of water level is also a possible adverse effect on the agricultural schemes along the Blue Nile; the Gezira scheme, one of the largest irrigation projects in the world. The objective of this study is two-fold. The first objective is to identify cities and villages near the Sennar Dam (in Sudan) that may be affected by potential fluvial (river) floods. The second objective is to select rainwater-harvesting (RWH) sites that can be used for water-supply backup while minimizing possible water-level reduction. RWH is in line with UN Global Sustainable Development Goals (UN-SDG). The use of remote-sensing techniques has enabled access to unique sources of information (satellite images and DEM) to better characterize hazards and risks, and a GIS was used as an effective modeling and visualization tool.Keywords: Fluvial flood, Rainwater harvesting, Sennar Dam, Sudan, Remote sensing, GIS