f Geohazards in Greater London identified from geological and Persistent Scatterers data

In the framework ofthe EU FP7 PanGeo project, the 27 European National Geological Surveys are generating validated geohazard layers depicting areas of observed and potential ground instability for 52 of the largest towns across Europe. These will be made freely accessible and usable via a portal to the general public, local authority planners and regulators, geological surveys, geoscience institutes and policy-makers involved in the assessment, mapping and management of geological risks. The first product generated by the British Geological Survey (BGS) covers the administrative area of Greater London (~1,580 km2 ), and consists of a polygon-wise Ground Stability Layer showing location, extent and typology ofthe observed and potential geohazards, and associated Geohazard Description document, a supporting report which describes in detail the geological setting and places of interest affected by each geohazard, the level of confidence in the interpretation and digitization of the polygons, and any evidence supporting the interpretation. The identification of geohazards in London is performed through combined interpretation of geological, land use and other geospatiallayers and datasets available at BGS, together with satellite ERS1/2 and ENVISAT Persistent Scatterers (PS) ground motion data for 1992-2010, generated by Fugro NPA Ltd. The PanGeo product identifies ~450 km2 of observed and -1,240 km2 of potential geohazards over Greater London. Potential for natural ground movements (shrink-swell clays, and compressible ground) is observed for the majority of the area. Geohazards observed through the PS data include both natural processes (compaction of the River Thames sediments) and anthropogenic instability due to water abstraction and recent engineering works (e.g., Jubilee Line Extension). Integration with the GMES Land Theme's Urban Atlas shows the landcover/landuse polygons influenced by such hazards, and supports the end-users in the management of geohazards and induced risks within the concerned area. 62