Abstract's details
What wide swath altimetry has made visible: two case studies of flood events
Event: 2025 SWOT Science Team Meeting
Session: Hydrology: Open Science & Applications
Presentation type: Oral
Even though the SWOT’s revisit time in its nominal 21-day cycle makes it inadequate for most operational applications in flood mapping and early warning, its data have opened up new perspectives for improving our understanding of floods using swath altimetry. Firstly, the two-dimensional map of water surface elevation makes visible small spatial variations in the water level that provide new information about the event. For example, in the Saint-Omer flood event case study, the difference in water surface elevation (WSE) between two adjacent flooded areas highlighted the role of a small dike that isolated them at the beginning of the flooding.
Combined with accurate topographic data, local water depth derived from SWOT’s WSE is also very valuable information because it is directly related to the socioeconomic impact of the flood.
Finally, the 1-day cycle Cal/Val phase provided an opportunity to observe major flood events such as the Kakhovka Dam destruction in 2023. At these large spatial scales, the 1-day time series of WSE maps reveals the temporal dynamics of flood propagation.
The exploitation of SWOT data for flood applications requires using the Level-2 HR Pixel Cloud product, or even the upstream SLC products if necessary. Work to improve the flood-specific treatment of the Pixel Cloud is still ongoing, especially to improve data filtering in urban areas. Beyond that, the key challenge will now be to figure out how to extract useful information from these water level maps. In this context, recent and upcoming developments in high-revisit SAR imaging and nadir altimetry constellations, as well as high-resolution global and updated Digital Elevation Models (CO3D mission), open up promising possibilities for synergies with Wide Swath altimetry data.
Our presentation will focus on 3 case studies including consolidated results from the 2023 Kakhovka Dam and 2024 Saint Omer floods (France) events presented at the 2024 EGU conference [Gasnier et al, 2024]
Gasnier, N., Fjørtoft, R., Zawadzki, L., Desroches, D., Pena Luque, S., Claire, P., Barroso, T., and Nicolas, P.: Leveraging SWOT's water elevation pixel cloud to comprehend analyse the spatial dynamics of flood events, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13278
Back to the list of abstractCombined with accurate topographic data, local water depth derived from SWOT’s WSE is also very valuable information because it is directly related to the socioeconomic impact of the flood.
Finally, the 1-day cycle Cal/Val phase provided an opportunity to observe major flood events such as the Kakhovka Dam destruction in 2023. At these large spatial scales, the 1-day time series of WSE maps reveals the temporal dynamics of flood propagation.
The exploitation of SWOT data for flood applications requires using the Level-2 HR Pixel Cloud product, or even the upstream SLC products if necessary. Work to improve the flood-specific treatment of the Pixel Cloud is still ongoing, especially to improve data filtering in urban areas. Beyond that, the key challenge will now be to figure out how to extract useful information from these water level maps. In this context, recent and upcoming developments in high-revisit SAR imaging and nadir altimetry constellations, as well as high-resolution global and updated Digital Elevation Models (CO3D mission), open up promising possibilities for synergies with Wide Swath altimetry data.
Our presentation will focus on 3 case studies including consolidated results from the 2023 Kakhovka Dam and 2024 Saint Omer floods (France) events presented at the 2024 EGU conference [Gasnier et al, 2024]
Gasnier, N., Fjørtoft, R., Zawadzki, L., Desroches, D., Pena Luque, S., Claire, P., Barroso, T., and Nicolas, P.: Leveraging SWOT's water elevation pixel cloud to comprehend analyse the spatial dynamics of flood events, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13278