Improved Terrain Modelling to aid flood mapping in coastal cities

Coastal areas are recognized as the most at risk due to climate change. They exhibit low-lying elevation, very high urban density and valuable economical assets. Sea level rise, storm events and coastal floods that are increasingly frequent and more powerful will increase damage to fragile coasts. Human activities (especially the reduction in natural defences), sediment balance and natural phenomenon are disrupted and increase the coast’s vulnerability.

As part of the GDA-DR initiative, we aim to produce some new indicators derived from EO to better understand the coastal system. As part of these new indicators, improved flooding maps are being developed using corrected elevation data and additional layers to better represent water behaviour in coastal cities. 

• The Copernicus DEM GLO-30m is proving too crude to provide suitable flood modelling. It offers an accuracy of 4m, leading to an accuracy of earth features’ localization of less than 2.6 m. By using LIDAR measurements from the ISS-borne GEDI sensor and additional altimeter missions such as ATLAS on-board the ICESAT-2 satellite, we provide an improved and corrected DSM and DTM
• Additional layers produced for DEMs correction are used to improve floods modeling such as land cover maps to extract drag coefficients and 3D settlement layers to take into account channelling effects.

This new approach can provide improved flood maps to better support flood mitigation planning. We propose to present DSM and DTM, for Dili in Timor Leste, based on the most recent space-lidar data, GEDI (2019-2021) and of IceSAT-2/ATLAS (2019- on going) and hoe those new DEMs can impact flood risk assessment.