Floods can be hugely destructive, but they also offer opportunities for farmers and fisherfolk. If their frequency and extent can be measured, then we will be better able to mitigate costs and maximise benefits. Digital geospatial flood inundation mapping is a powerful new approach for flood response that shows floodwater extent and depth on the land surface. IWMI research will evaluate this new technology and develop a prototype flood inundation map for South Asia. Also discussed is a project to flood map and model in a spate irrigation system in Sudan.