High-Resolution InSAR-based DEMs for Flood Hazard Analysis: Advances from the RESCUE_SAT Project

The increasing frequency and intensity of flood events driven by ongoing climatic changes are exerting substantial pressure on ecosystems, productive activities, and the resilience of critical infrastructure. As a result, climate-change adaptation strategies are progressively focusing on mitigating their impacts. Numerical hydraulic and hydrological forecasting remains the principal tool for supporting prevention and protection policies, relying on Digital Terrain Models (DTMs), including Digital Elevation Models (DEMs), and land-cover information. In this context, satellite remote sensing has the unique ability to cover large spatial extents with high spatial resolution (below the meter scale) and, at the same time, to provide updated data with each new orbital acquisition. In hydrological modelling, coarser terrain data (approximately 10 m) are generally sufficient for simulating rainfall-runoff dynamics, whereas hydraulic models that resolve flood propagation require substantially finer spatial detail, typically on the order of 1 m.

The RESCUE_SAT project (Agreement n. 2025-2-HB.0), funded by the Italian Space Agency (ASI) under the “Innovation for Downstream Preparation for Science” (I4DP_SCIENCE) programme, integrates advanced hydrological and hydraulic analyses from the RESCUE model [1] with multi-scale satellite Earth Observation (EO) data. Its primary objective is to enhance flood-modelling capabilities by assimilating high-resolution EO information into rainfall-runoff simulations, thereby enabling a unified framework capable of representing both large-scale hydrological behaviour and local hydraulic processes, including flow interactions with structures such as bridge piers and embankments. By integrating the computational efficiency of DEM-based analyses with advanced hydrological and hydraulic modelling, RESCUE_SAT aims to generate physically based flood maps while maintaining time-effective workflows [2].

To this purpose, ASI’s COSMO-SkyMed (CSK) SAR products are processed using an InSAR approach to derive DEMs with a spatial resolution of 3 m over selected case-study areas in the Latium Region, Italy. The resulting DEM is then compared with other elevation products, including the SRTM v3 DEM (3 arc seconds, with a 90 m spatial resolution) [3] and a LiDAR-derived DEMs from the National Geoportal - MASE [4] with a spatial resolutions of 1 m. The CSK DEM is expected to enhance the detection of flood-prone areas, particularly where natural flow paths interact with infrastructure. RESCUE_SAT also incorporates ground-based GNSS and UAV surveys, integrated during calibration and validation to characterize local-scale processes in settings where infrastructure influences surface-water dynamics, thereby highlighting the value of multi-source satellite data for medium to large‑scale flood-risk assessment and infrastructure resilience.

References

[1] Pavesi, L., et al., (2022). RESCUE: A geomorphology-based, hydrologic-hydraulic model for large-scale inundation mapping. Journal of Flood Risk Management, 15(4), e12841

[2] Gagliardi, V., et al., (2025). Enhancing hydraulic risk assessment using next-generation satellite remote sensing: the RESCUE_SAT project. Vol. 13671. SPIE, 2025

[3] Farr, T. G., & Kobrick, M. (2000). Shuttle Radar Topography Mission (SRTM) produces a near-global digital elevation model. Eos, Transactions of the American Geophysical Union, 81(48), 583–585.

[4] Ministero dell’Ambiente e della Sicurezza Energetica (MASE). LiDAR data from PST-Geoportale Nazionale