Efficient water area classification using Radarsat-1 SAR imagery in a high relief mountainous environment

It is important to determine quickly the extent of flooding during extreme cases. Even though SAR imagery with its own energy sources is highly applicable to flood monitoring owing to its sensitivity to the water area, topographic effects caused by local terrain relief must be carefully considered before the actual classification process. Since backscattering coefficients of the shadow area in high relief regions are very similar to those of the water area, it is essential to regard these areas before and after the classification procedure, although the process is a difficult and time-consuming task. In this study, efficient and economical methods for water area classification during floods in mountainous area are described. We tested five different cases using various synthetic aperture radar (SAR) image processing techniques, texture measures, and terrain shape information such as elevation and slope. The case whereby the SAR image was classified with the local slope information exhibited the best result for water area classification, even in small streams of different elevation categories. Consequently in mountainous areas, the combination of a SAR image and local slope information was the most appropriate method in estimating flooded areas.