Mapping the Valencia Floods with Sentinel-1

The recent floods in Valencia have caused extensive damage. To create a map of the affected areas, Sentinel-1A SAR (Synthetic Aperture Radar) imagery was utilized, offering reliable data to map and identify flooded zones, even under challenging weather conditions and cloud cover. For this analysis, two SAR images from Sentinel-1A were chosen: a pre-event image acquired on October 19, 2024, and a post-event image taken on October 31, 2024 . These dual-polarization images were crucial for detecting changes in water coverage across the region.

The processed images were combined to create an RGB composite map that effectively visualizes the extent of the flooding. The red channel was assigned to the VH polarization of the pre-event image, while the green and blue channels were sourced from the VH polarization of the post-event image. This specific RGB configuration provided a clear visual distinction between different states: red areas indicated newly flooded zones where water appeared only after the event, while black areas represented stable water bodies present in both pre- and post-event images (Figure 1).

The resulting flood map outlined the impacted areas effectively, allowing for a clear differentiation between normal and flooded zones.

Reference: ESA Echoes in Space – Hazard: Flood mapping with Sentinel-1 https://www.youtube.com/watch?v=derOXkPCH80

Written by giovanna palumbo