Following the disastrous floods that occurred in October 2018, Aude French department has become a pilot territory for the use of satellite images following hydro meteorological disaster, contributing to the development of territories more resilient to extreme events. Since end 2018, a collaborative work, anchored in reality, has been carried out between the departmental directorate for territories and sea (DDTM Aude) and CNES, through in-depth analysis of extreme hydro-meteorological events, aiming at developing a future Flood Observatory for Resilient Occitanie.
The Copernicus Climate Change Service (C3S) decided to illustrate the strength and potential of both SCO and Copernicus through a dedicated Demonstration Case under the umbrella of SCO, built on experience gained on Aude department. Using C3S, but also Copernicus Emergency Management Service (CEMS) data and products, together with other various data, the aim is to derive decision and policy planning tools to assess and evaluate the impacts of climate change on a concrete use case in Europe.
The Flood Observatory for Resilient Aude and Occitanie (FORO) will be created to capitalize on the results of this project and promote iterations between the different actors.
FLAude builds on previous work on Aude to extend its territory, duration and scope, addressing impacts and necessary adaptations on the Occitanie region, as well as medium and long term projections. The associated results and good practices will be profitable to the flood observatory, to other departments and regions networks in France (DDTM, DREAL, DEAL, EPCI), as well as to actors of the Ministry of Environment Satellite Applications Plan. The European and global replicability of the service will be addressed by using open datasets and tools offered by Copernicus DIAS and especially new C3S climate datasets.
FLAude will enable the creation of the basic treatment bricks, as well as the preliminary results, which will subsequently feed FORO. It will contribute to the understanding of extreme hydro-meteo phenomena and to the elaboration of methods for prevention and risk reduction, adapted to the use by local decision makers. The medium term objective will be achieved in the framework of the FORO platform, while the longer term objective is to be able to respond, in metropolitan France, overseas French territories and abroad, to the needs of regional and local administration affected by extreme hydroclimatic events.
The exemplary nature of the FLAude demonstrator is guaranteed through the implementation team, ensuring links
- with local, department and regional users, led by DDTM Aude,
- with Météo-France key partner for climate expertise in France and experience in C3S data use for global replicability of the service, and
- with public policy experts and academics (SGEvT/University Toulouse2 Jean Jaurès) in order to guarantee the suitability and acceptability of these tools by authorities and decision makers.
Long term evolution of flood risk and projections in the future will be provided through new European or Global C3S products for past events analysis and climate projections evaluated with Météo-France climate references, helping decision makers to better assess decisions to be considered in the future.
TERRITORIES FOR EXPERIMENTATION
- Aude department, France
- Pyrénées Orientales department, France
- Occitanie region, France
Related SCO Projects
- French satellite Pléiades (70 cm resolution)
- European satellites Copernicus/Sentinel-2 (10 m resolution) and Copernicus/Sentinel-1 (10 m resolution)
- Historical Spot and Pleiades archive (Spot World Heritage)
- Other free and open satellite images data sets: Landsat
- C3S data and models: ERA-5 Land and/or UERRA
- EuroCordex projections
- Meteo France data and models on DRIAS portal
- Space data portals: PEPS, IR DataTerra (THEIA, AERIS, ...), etc.
- Copernicus Services: C3S, EMS (RMS, RRM, EFAS), CAMS, Land
- Large number of territorial data set: land use maps, population maps and densities, agricultural fields national registry (RPG), etc.
RESULTS - FINAL PRODUCTS
- Damage assessment maps derived from Earth Observation (EO) High and Very High Resolution images after major extreme events on Aude department during the project duration.
Assessment of Log jams:
With an artificial intelligence algorithm based on the differences between two high resolution images (before and after the flood) and trained on examples of log jams manually annotated, predictions of log jams were made for two major flood events (15-16/10/2018 and 22-23/01/2020).
Examples for the 2018 flood event:
The covered area corresponds to the Pléiades images (PHR) acquired just one month after the flood, which represents approximately half of Aude French department.
- Climatic analyses & Projections of hydro-climatic flood events in Occitanie using C3S Climate Data Store (CDS) and Météo France data
Three types of climatic variables were taken into account to characterize flood events: precipitation, soil moisture and river discharges.
The selected C3S products based on ERA5Land, UERRA and CMS EFAS were evaluated by comparison with the reference products of Météo-France by considering time steps and specific indicator adapted to the particular floods of these Mediterranean regions.
The several C3S and Météo-France products were presented on two flood events of October 2018 and November 1999 while the evaluation was carried out about twenty of the strongest events observed in this territory in the last 20 to 50 years.
The UERRA product, which benefits from an assimilation of precipitation observations, shows good qualities for the restitution of the local climate with a reduced bias in terms of maximum daily precipitation versus Météo-France reference, explainable by the differences in spatial resolution of these two products.
Figure 5 extracted from the report shows the good capacity of the UERRA data to identify major flooding events in the territory by adapting the threshold to the resolution of the product.
The ERA5-Land products roughly restituate the extent of rainfall over this zone. Intensity of extreme rainfall events are strongly underestimated on the whole area, particularly in the mountainous regions where maxima are particularly biased. Concerning 3-hour cumulative precipitation, correlation is moderate between ERA5-Land data and the Météo-France reference.
For soil moisture analysis, the three C3S products analyzed UERRA, ERA5Land, EFAS show good skills compared to the best Météo-France analysis.
In terms of river discharges, results are roughly proportional with watershed sizes simulated by the products. Poor scores were found for watersheds of less than 1000 km2.
- Provision of Climatic analyses & Projections Tools on CDS
- Recommendations on EO, C3S, Copernicus Emergency data & products use for local flood risk management
- Technical material derived from EO and C3S to enlighten and support Public Policy dialogue
- Preliminary guidelines for the development of public policy documents incorporating information and parameters derived from EO and C3S
- FLAude Demonstration Case on C3S portal integrating products (maps, graphics) on past & future climate indicators about extreme precipitation events.
23/02/2021: Focus on FLAude