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Flexth: the open source tool to estimate the depth and extent of floods

JRC innovative open source tool (FLEXTH) to improve floods mapping

Published on: 27/11/2024 Last update: 29/11/2024 News
Source: Unsplash

Flexth is an innovative open-source tool developed by the European Commission's Joint Research Centre (JRC) to estimate water depth and improve flood mapping, particularly for satellite-derived maps, by incorporating terrain topography. This groundbreaking algorithm, proposed by researchers Andrea Betterle and Peter Salamon, represents a significant advancement in understanding and mitigating flood impacts. By enhancing flood area predictions, it supports more effective emergency management across the EU.

Key Features of Flexth in Flood Estimation

Recent advances in satellite remote sensing and data processing have transformed flood mapping. Satellites provide crucial insights into flood dynamics, such as water extent and inundation progression over time. However, certain limitations persist, including reduced visibility during cloudy conditions or nighttime, and the inability to estimate water depth.

As noted by Betterle and Salamon: 

'Water depth is the difference between the elevation of the water surface and the underlying terrain [...] considered to be the most informative proxy variable for quantifying flood impacts'

Traditionally, water depth was estimated using ground-based observations and manual measurements, methods that are time-consuming and offer limited spatial coverage, especially for large areas.

Flexth addresses this challenge by integrating topographic data to enhance flood maps. It expands inundation predictions to areas prone to flooding based on elevation and calculates estimates of water levels and depths, filling a critical gap in flood impact analysis.

How has Open Source contributed to the Flexth development?  

The research article ‘Water depth estimate and flood extent enhancement for satellite-based inundation maps’, published in the journal Natural Hazards and Earth System Sciences (NHESS) under a Creative Commons Attribution 4.0 License, explains how the FLEXTH algorithm is available as an open-access Python script at code.europa.eu, because FLEXTH was designed  ‘to run in an unsupervised mode in a reasonable time over areas of several hundred thousand square kilometers’.

Flexth has to be licensed under an open source licence, as stipulated in the Commission Decision 8.12.2021, whose repository is accessible in Code.europe.eu. On a computational level, Flexth uses leverages the Open Source Computer Vision Library, to facilitate an facilitating efficient image processing of large raster datasets. OpenCV code is accessible on Github

Future integration

The JRC is currently working to integrate Flexth into the Global Flood Monitoring (GFM) system within the EU’s Copernicus Emergency Management Services (EMS). This integration will allow civil protection and emergency response teams across EU 

For more details, the Flexth code is available on code.europa.eu, and the original research article provides further insights.