Use of ERS-1 data for the extraction of flooded areas

✍ Scribed by SANDRINE DELMEIRE

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 485 KB
• Volume: 11
• Category: Article
• ISSN: 0885-6087
• DOI: 10.1002/(sici)1099-1085(199708)11:10<1393::aid-hyp528>3.0.co;2-n

✦ Synopsis

The aim of this study, undertaken by Geoimage, was the setting up of a fast and precise location method of ¯ooded areas over two sites in southern France. The use of satellite imagery seemed to be the appropriate tool for this study.

Two types of ¯ood had to be distinguished: (i) an oceanic ¯ood, of long duration characteristic, and of low intensity on the Rhoà ne Valley, (ii) a torrential ¯ood, of short duration characteristic, but of high intensity, on the Var Valley. As we distributed of ERS-1 images over both sites, during the ¯oods, we could test our methodology. A multitemporal approach using ERS-1 images in PRI mode, acquired before, during and after the ¯ood, was set up. In the case of oceanic ¯ood, the radar images characteristic answers, enabled us to extract and identify areas under water at each date of acquisition of the images. Therefore, if we distribute images at each step of the ¯ood, its evolution can be precisely reconstituted (in terms of time and surface). In the case of torrential ¯ood, it is more dicult to localize the ¯ood with precision. This can be explained by the change of water surface, which has a large swell in this case. Radars are sensitive to these changes in the turbidity, an interaction occurs and thus the results were `turned o'. Nevertheless, simulation studies from other satellite data make possible the location of more or less strong hydrological risk accident areas.