@@tsaonegoikantswemang5044 in general, water level all over the globe is maximum 15 feet and if convert it to meters will be 4.6m=5m , so, after shoosing your study area and you download your DEM wich is your SRTM image , you going to have max and min , and will know your maximum , in general , you need to make senarios ,for example to estemate water level rising to 1m/2m/5m wich is the flood result of each senario ,after that you can arcscene(arcgis) or qgs2threejs(qgis) to make an animation to see the evolution of the flooding and which areas are in deep risque