The contribution of the Pleiades imagery to the mapping of stakes and their vulnerability to torrential floods: The city of Arequipa, Peru

Since the 1980s, the increasing quality of satellite images aimed at the observation of the earth, open new possibilities for photo-interpretation in risk assessment of natural hazards in the context of prevention, monitoring and damage analysis. On February 8lh 2013, a flash flood inundated adjacent areas to the Avenida Venezuela drainage in the city of Arequipa, Peru, affecting more than 280 buildings, and 23 bridges. At the example of this event, this study uses high spatial resolution (HSR) Pléiades images to improve the mapping of exposure of elements at stake and of their vulnerability to flash flood hazard. Ground control is provided by a field survey realized after the flood event of February 2013. The objectives of this work are fourfold: (1) use HSR Pléiades images to map landuse in a complex urban environment; (2) test the use of supervised classification for semi-automatic object identification on Pléiades imagery using Monteverdi; (3) compare the quality of results and evaluate the potential of computer-assisted mapping techniques and (4) identify flood impact on the channel itself on the 2013 image. Results confirm a clear improvement of vulnerability mapping accuracy at large scale based on the photo-interpretation of Pléiades images. Exposed elements can be better delimited and the combination of semi-automatic classification and manual mapping has proven to be an optimal compromise for an accurate and rapid risk assessment.