Evolution of coastlines on a global scale by satellite with application to the study of the impact of climate change – GLOBCOASTS

The current lack of information on coastal underwater topography is linked to major technological and scientific barriers leading to unacceptable uncertainties in the civilian (coastal management, structures, crisis management, natural hazards, coastal vulnerability - erosion/submergence) and military (projection of amphibious operations, sea state forecasting) fields. Hydrographic services such as the Shom in France or the UKHO in Great Britain survey less than 1% of their continental shelf each year, resulting in a recurrence of surveys over the years. These high-resolution SMF and LIDAR surveys cover no more than a few thousandths of the world's very shallow waters, and the very high variability of these environments poses the problem of the validity of these surveys (Report C-55 on the survey census by the IHO, April 2019). Satellite methods have mainly focused on bathymetry by inversion of the radiometry of satellites such as SPOT and Landsat. The contribution of fast, inexpensive and efficient methods is needed for studies on the variability of the seabed such as beach edges or the dynamics of underwater dunes. This need is even more important for areas made inaccessible by conflicts, for areas too far from base ports or too little frequented by ships to be surveyed. And most coastlines have not been surveyed in the last 50 years. The GLOBCOASTS project is based on the results of R. Almar's thesis (DGA thesis award 2011) which, by analyzing the optical signal of video cameras, has made it possible to invert the wave signal during the measurement campaigns of the PEA ECORS to calculate the bathymetry. The ANR ASTRID COASTVAR has continued this approach by focusing on measurements by drone and extending the analysis of processes to calculate the dynamics of the coast of West Africa and Vietnam. GLOBCOASTS aims to generalize to the global scale these innovative satellite operational methods based on the tool developed to lift this scale lock for the first time. Beyond the new composite static global coastal bathymetry already realized as a proof of concept, this tool will allow for the first time to 1- provide a climatic evolutionary bathymetry, with seasonal (summer/winter), interannual and trend statistics, updated during major events (tsunamis, typhoons, hurricanes), 2- to provide land-sea maps for force projection operations and to update existing maps. This information will allow the very first evaluation of the evolution of the coasts on a global scale with climatic and anthropic influences. There is a pressing need for a fast and efficient satellite remote sensing tool for estimating coastal bathymetry for any coastline in the world.
The objective of GLOBCOASTS is for the first time to obtain coastal bathymetry by satellite with information on temporal evolution. We will capitalize on the acquired methodological expertise and on these new available satellite observations, offering a technological, operational and scientific breakthrough, with a spatio-temporal coverage of coastal bathymetry never equaled. With a TRL level of type 3 at the end of the project with a proof of possibility of use of space for the quantification of bathymetry on a global scale and in time, for a use beyond the project via an operational and commercial implementation (ASTRID Maturation support targeted in 3 years), the market including a broad spectrum of applications. The GLOBCOASTS project is structured on a strong research axis (LEGOS coordinating laboratory) with easy access to space data and their analysis by CNES and an expert partner for the qualification of bathymetric products (Shom).