The EU Joint Research Center (JRC) has developed a tool to estimate flood water depth and improve the accuracy of flood extent maps by combining satellite images with topographic data.
Inland flooding is a key risk for Europe due to the extent of settlements exposed, the frequency of the hazards, the risks to human lives associated with flash floods and the limited adaptation potential to pluvial flooding. A warming above 3°C could double the costs of damage and people affected by precipitation and river flooding. Flood water depth is a critical factor in assessing the impact of a flood, in particular when it comes to assessing the damage caused to buildings or other infrastructure. Knowing flood water depth can also support rescue operations by helping to decide which means to allocate (e.g. helicopter or boat) and the equipment and quantity to use (e.g. hoses and water pumps).
In September 2024 devastating floods threatened lives and livelihoods in Central and Eastern Europe. Maps from the Copernicus Emergency Management Service (CEMS) have shown the extent of the damages in Germany, Poland, Slovakia, Romania, Hungary and Austria. Until now, water depth estimations relied heavily on ground-based observations, as satellites cannot sense water depth. A JRC-developed tool, still under testing, and foreseen as a future evolution in CEMS will improve flood delineation accuracy and floodwater depth.
Satellites images are already used to map flooded areas to monitor the evolution of floods, and support recovery efforts. However, satellite images have also limitations as cloud cover, dense vegetation or large infrastructure in urban areas can obstruct or degrade the signal of satellite sensors. In addition, in the case of floods, there’s another drawback as satellites cannot sense water depth. To address these gaps, JRC scientists developed the Flood Extent Enhancement and Water Depth Estimation Tool (FLEXTH). The tool combines satellite-derived flood extent maps with readily available topographic data to rapidly estimate flood depth and spread the flood extent into areas not covered by the satellite sensor.
