| Summary: | Land subsidence presents a global problem to many communities around the world, and the effects are predicted to get more substantial in the coming years due to the ensuing impacts of climate change. Although most observed land subsidence is as a result of human activities, geological deposits naturally undergo forms of subsidence without this impetus and measurements of the potential natural subsidence rates are important for planning purposes, risk management, and hazard mapping. Over the last few years there has been an increase in the availability of wide-are mapping of ground motion velocities from initiatives such as the European Ground Motion Service (EGMS). This has been made possible by the combined advances in Synthetic Aperture Radar satellite technology, sophisticated Interferometric Synthetic Aperture Radar (InSAR) processing algorithms, and the development of powerful cloud computing technologies that are capable of processing huge amounts of data.
The purpose of this dissertation project is to estimate the potential rates of natural subsidence stemming from dissolution, compaction, and shrinkage throughout Britain, by integrating InSAR velocities from the EGMS and derived maximum potential subsidence rates from the British Geological Survey project SubCoast. Several ancillary datasets were included to contextualise regions of motion to understand the underlying mechanisms, and correlations were analysed between average InSAR velocities and geological deposits to link the ground motion to natural processes.
The national-level analysis showed that the dominant trend of land subsidence in Britain is as a result of large-scale crustal movements, which are inline with Post-Glacial Isostatic Adjustments (GIA) as measured by continuous GNSS stations. Local scale analysis of the Greater London area determined the principle sources of motion as a result of groundwater abstraction and underground construction work, with other significant motions due to compaction of alluvium deposits surrounding the Thames estuary. At both a national and local level, the underlying geology had a minimal correlation with the observed motions. This highlights the possibilities of conducting ground deformation analysis at scale, through the use of large downstream data products.
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