Using disaster footprints, population databases and GIS to overcome persistent problems for human impact assessment in flood events

Preventing disasters and their consequences is crucial to protect our societies and promote stability. Reliable information on impact is essential for an in-depth analysis of the factors that lead to disaster and for better disaster prevention and preparedness policies. At present, the estimation of the population exposed to natural hazards is based on proxies of their physical footprint such as flooded regions or watersheds. Satellite hazard footprints, combined with population and disaster impact data, can provide an impact assessment of higher precision. We report here on the procedure to combine such data using GIS methods and compare these estimates with those obtained using a previous approach. We found that the process is feasible, although there were limitations in the matching of disaster databases and possible problems of estimation when the data had different resolutions. In half of the events, the watershed approach largely overestimated the population physically exposed to floods. We conclude that the systematic production of footprints, as well as better methodologies for human impact measurement, would improve our understanding of disaster impacts and thereby strengthen disaster preparedness.