Surface water detection and flood mapping using optical remote sensing and water-related spectral indices

The use of multispectral satellite imagery for flood mapping and river monitoring is a fast and cost-effective method that can benefit from the growing availability of medium-high-resolution and free remote sensing data. Since the 1970s, several satellites are observing the Earth surface supporting water detection studies and flood management. In addition, many techniques exploiting different spectral indices have been proposed in the literature. Considering the high number of available sensors and their differences in spectral and spatial characteristics, this work aims to examine the applications of satellite remote sensing for water extent delineation and flood monitoring. Focusing on freely available optical imagery, this study presents a discussion of the most used satellites for flood and wetland mapping to highlight trends of current research studies. Furthermore, performances of the most common spectral indices for water segmentation are analysed first qualitatively, based on evidence obtained from a significant literature review, and then quantitatively by comparing different water-related index algorithms applied to a real case study. Performance assessment is carried out to provide an overview of the best sensor-specific spectral index in detecting surface water and expressed in terms of overall accuracy (OA) and Kappa coefficient.