Satellite monitoring of the coastline: change detection and support for coastal planning
Coastal erosion and mean sea level variation are slow but continuous evolutionary processes that directly affect critical infrastructure, port areas, sanitation networks and coastal urban zones. Their systematic monitoring requires time series of high geometric coherence, a condition that Earth observation systems from orbit satisfy in a structural manner: they enable data acquisition over extensive coastal strips with regular revisit periodicities and a reproducible acquisition geometry, which is essential for detecting coastline displacements on the order of metres over periods of years or decades. Differential synthetic aperture radar interferometry (DInSAR) techniques and multi-temporal optical image correlation are the methods with the greatest operational application in this field. The former enables quantification of coastal land subsidence with centimetric precision, a phenomenon that acts as an amplifying factor for flood risk in low-lying areas. The latter facilitates the delineation of the coastline at different historical moments, enabling analysis of retreat rates or sedimentary accretion. Both techniques present known limitations: interferometric coherence degrades in areas of dense vegetation or soft soils, and coastline classification in optical images is conditioned by the tidal state at the time of acquisition, which requires correlation with tide gauge data or tidal models in order to obtain comparable results. Complementarity with field data is an operational requirement, not an option. Coastal bathymetry surveys, tide gauge station records and beach topographic profiles provide the altimetric reference necessary to validate and calibrate products derived from satellite observation. In the absence of this integration, results lack the metrological traceability required in coastal planning processes or in technical reports supporting investment decisions on protective infrastructure. From a regulatory and public policy standpoint, coastal administrations of the European Union are subject to planning frameworks that incorporate flood and erosion risk assessments with time horizons of several decades. The availability of historical satellite series, some with retrospective coverage exceeding twenty years, provides these processes with an objective and reproducible evidence base. For operators of critical infrastructure in coastal environments, continuous satellite monitoring of the coastline represents a tool to support geotechnical risk management and the prioritisation of maintenance or structural reinforcement actions, independently of the administrative scale at which each organisation operates.
NASSAT - Network Satellite Systems