Monitoring coastal wetland evolution using satellite imagery: The EO4 wetlands project labeled by the Space Climate Observatory

Related to the Interreg Polder2CS research project, which includes several research works on marine flooding and protection devices carried out at a demonstration site in the Netherlands, the EO4Wetlands project aims to monitor the regeneration of a coastal wetland through a combination of different monitoring methods. .

EO4Wetlands is one of two Cerema-led projects labeled by the Space Climate Observatory (SCO) France in 2022, along with Pleiades4UrbanFlood.

Combine images from different satellites

The Intereg Polder 2CS project, in which Serema participates, makes it possible to conduct several research projects around de-polderization at the Living Lab Hedwij-Prosperpolder (LLHPP) site on the Dutch-Belgian border, which is gradually being returned. the sea Assessed, especially that of cuirassiers, the tests that Cerema contributed to, as well as the occurrence of dike failures. Focus on other tasksObservation of transformation in polder wetlands.

In order to better study the evolution and role of wetlands and the land-sea interface, Cerema is piloting the EO4 Wetland project in collaboration with Stoa (the Foundation for Applied Water Research in the Netherlands), in partnership with Cerema Geomatics and the Mathematical Laboratory of INSA Rouen), Department of Mobility and Public Works of the Flemish Region of Belgium. , Q Leuven (Catholic University of Leuven), Frans Degues and GIP Seine Aval.

The aim of using the project is one Combination of images from different satellites which makes it possible to estimate more precisely certain parameters such as biomasstheir Biological and geochemical functionsThe water pot Vegetation and critical zones [1] :

  • Sentinel-1 (radar image, revisit time of 5-6 days),
  • Sentinel-2 (multispectral image, 5-6 day revisit time) monitors the vegetation through a classification based on land cover developed by Cerema to monitor the evolution of polders after dike collapse.
  • Sentinel-3 (thermal infrared imager, revisited twice a day) for surface temperature monitoring to identify water regions.
  • Landsat (multispectral and thermal infrared images, 14-day revisit time).

Based on these parameters:

  1. classification of visible and near infrared data through NDVI (Normalized Difference Vegetation Index) and/or NWDI (Normalized Difference Water Index);
  2. Its follow-up dynamic Because of variations in surface water content, such as wetlands, with radar data;
  3. Application of thermal infrared data to existing classifications such as inferring surface temperature changes Daily dynamics swamp
Overlaid satellite view and drone orthoimage of polder site

The project methodology will follow various steps. First, Sentinel-2 images will be used for a development classification system Track is based on land coverEvolution of plants Through time and space after dike destruction. This component will be done in collaboration with LMI. A new understanding of evolution temporal and spatial Plants and wires Biochemical functions Will provide information that can be applied to other wetlands around the world.

The high revisit time will allow studies of the polder by the SLSTR (Sea and Land Surface Temperature Radiometer) sensors on board Sentinel-3A and 3B.Daily evolution of surface temperature with a medium resolution of 100m per pixel. This will give indirect information about surface soil moisture.

In addition, during flooding and/or sea breaking events, the spatial evolution of the shoreline can be constrained using a combination of Sentinel-1 and -3 for Sentinel-3 data or in cloudy conditions. In fact, the soil moisture level will specifically make it possible to understand the progress of moisture in the area. Thanks to the Landsat and Sentinel-3 image archives, historical research can also be done to analyze the evolution of wetlands in relation to climate change.

Towards a mapping tool for wetland monitoring

Will allow spatial evolution of vegetation and surface temperatureStudy the advantages and disadvantages of the methods combination Satellite information Obtained with very high spatial resolution images the drone in the visible and thermal infrared spectrum. In order to bridge the gap between scales Drones and satellites, we will rely on:

  1. In situ recording of humidity and surface temperature at specific locations in the LLHPP polder, to calibrate satellite data.
  2. Use of ECOSTRESS on the International Space Station (spatial resolution of 70 m), which can act as a bridge between SENTINEL-3 and drone observations in thermal infrared.

All these developments will be pooled through one development Operational Mapping Tool for Wetland Monitoringbased on Automatic recognition of changes in surface conditions at different spatial (satellite, drone and in situ) and temporal scales. It will primarily be aimed at the managers of the depolarized zones, who will provide their feedback as users. It can be useful for other managers of wetlands and tested with partners in different regions, for example in the Camargue, in the Rhône basin or in Belgium, as well as for managers of protective structures (dykes).

This project is an opportunityObserve wetland function as a buffer zone to deal with its effectsSea level rise In the context of climate change as well as restoration of a large wetland.

For Cerema, the ENDSUM research team (non-destructive evaluation of structures and materials) and the Cerema Satellite Center (Occitanie Territorial Department) are involved in this project.

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