Restoring and preserving flood expansion areas in the Upper Seine River Basin (France): The critical step of pre-field identification and characterization using LiDAR DEM data

Focusing on the Upper Seine River Basin (France), the study explores how a GIS tool can conduct pre-field analyses to identify potential flood expansion areas, addressing the demand from French authorities to map priority restoration and preservation areas. This paper also investigates the extent to which GIS digital data must be supplemented with field data to accurately define and characterize flood expansion areas. The methodology automates the identification and analysis of flood expansion areas using GIS and high-quality LiDAR DEM data and by extracting hydro-morphological parameters to evaluate a river’s connectivity to its floodplain. The results of the study are overall encouraging, as the automated analysis aligns well with both field measurements and hydraulic models used as control data. However, challenges remain, particularly in accurately estimating floodplain boundaries or river depth due to limitations of the input data. Addressing these will be critical to further enhance the tool’s precision and applicability. GIS-derived data can provide valuable insights into the functioning of Upper Seine River and its hydrological dynamics. While not developed to replace fieldwork, the tool establishes a general methodology that can be applied to hydrologically similar regions, ensuring a consistent approach to identifying and analyzing floodplain expansion areas. These findings are particularly significant given the fundamental role of flood expansion areas in mitigating flood risk, not only for downstream areas such as Paris, but also for local communities within the basin.