## 4 Discussion  
Sentinel 1 is highly effective to monitor infrastructures over the selected study sites. The response to seasonal soil moisture changes has been detected in the three of the infrastructures investigated. Observed surface deformation has been discussed as a function of both major soil group type, soil moisture change and the infrastructure's engineered design. Observed deformation across all sites reveal unique spatial and temporal patterns of measured movement, which have been discussed as  
Figure 5: Median ground deformation (mm) for 1579 PSI points over Meldon Quarry, Dartmoor National Park (50.716084, \(-\)4.026326). The Solid line represents loess-smoothed trend through the plotted median PSI values. Grey ribbon indicates the inter-quartile range of Median values. functions of the regional water use and the shrink swell potential of the different soil types studied. Sentinel 1 has proved itself to be effective at capturing these patterns across relatively wide study areas. This holds operational promise for the long-term monitoring of infrastructure using Sentinel 1 with PSI. It is evident that different soil types have an influence on observed infrastructure movement. This is particularly so for soils which are seasonally waterlogged and exhibit cycles of drying and wetting. Surface deformation of infrastructure has been observed to deform (along LOS) in all infrastructure classes analysed, mostly coinciding with the expected periods of soil shrink (summer months), and soil heave (autumn and winter months). The main soil groups included in this study which are prone to seasonal volume change are Ground-water Gley soils, Brown soils, Pelosols, and Surface-water Gley soils. All these major soil groups condition the heave and shrink of infrastructure, see Figure 4. Several surface deformation trends do not appear to follow seasonal pattern of shrink and swell. These unexpected results may be attributed to regional factors associated to the regional water regime such as intense agriculture, water abstraction, irrigation, and the presence of rivers and lakes. Direct analysis of these factors is out of the scope of this paper, yet for the Eastern study sites it should be noted that this region is under highly intensive agricultural land use, with significant drainage and irrigation, so it may not follow the expected seasonal response to soil moisture change. In such areas, variations from the expected deformation patterns are particularly evident for Brown soils (common agricultural soils) and Ground-water Gley soils in Peterborough, where a lag in infrastructure shrink is present, demonstrating a maximum subsidence in December 2016. This lag might be the result of active water management, such as irrigation and drainage from agricultural practices, which stabilises water content during summer and drains land during winter. These effects are particularly prevalent in the Fenlands (Eastern study sites) where the artificial pumping of water manages peat drainage [26]. Moreover, upon analysis of the soil moisture content for Redmerce (Figure 2), a low soil moisture was recorded until November that year, which further explains the lagged result seen in surface deformation over soils directly affected by the often anthropogenically controlled soil moisture content of this area. Remotely sensed soil moisture measurements would enhance the understanding of the relationships between surface soil moisture change, and observed ground movement using PSI, however this was also out of scope for this paper. In comparison, Bournemouth shows relative stability (Figure 4) in infrastructures. The main soil groups are Podzolic soils, Brown soils, Ground-water Gley soils, and Surface-water Gley soils. The observed stability can be attributed to the freely draining soils over permeable bedrock in Bournemouth, consisting predominantly of chalk, limestone, sands, and gravels. Variations in deformation rates are evident for Lithomorphic soils in Bath, Bristol, Grantham, Kings Lynn and Peterborough.