Researchers at the University of Nottingham have created a new UK-wide ground motion map.
The new UK-wide map covers a two-year period from 2015 to 2017 and was created using thousands of satellite radar images and an Intermittent Small Baseline Subset (ISBAS) analysis, a satellite remote sensing data processing algorithm.
It offers a detailed look at the UK’s shifting topography and highlights areas of hazards due to coal mining, soil compaction, landslides, coastal erosion, landfill subsidence and tunnelling for the London Underground.
The ground motion surveying system can obtain measurements over all urban and rural areas and provide a full picture of the moving UK land surface, and could be of significant interest to policymakers as well as the onshore oil and gas, civil engineering, insurance, mining and carbon trading sectors.
Nottingham University assistant professor in earth observation Stephen Grebby said: “With the new map we are able to better understand how the entire UK landscape is being affected by various natural and anthropogenic processes. Whilst providing us with detailed information to study the individual mechanisms of these processes, the technique also offers a means of identifying and mitigating any potential risk that these may also pose to infrastructure, society and the environment.”
Geomatic Ventures, the University spin-out company who applied the technology, chief technical officer Andy Sowter added: “This is truly the first of its kind. No one has ever mapped land motion across the whole of the UK quite like this before, encompassing the complete rural and urban landscape, and all from a satellite orbiting 800km above us.
”This unique image has revealed a dynamic, shifting, collapsing landscape dominated by unnatural, man-made activities such as our heritage in coal mining, agricultural practices and peatland management. It has implications for a whole range of industrial and governmental bodies including those in energy, infrastructure, environmental management and climate change but also demonstrates that a low-cost, operational solution to the monitoring of land surface dynamics at this scale is possible.”
What to look out for on the map
Large civil engineering projects such as the works at Kennington Park, part of the Northern Line extension, lie in a large subsidence bowl (red/brown on the map) measuring more than 500m across, just east of the Oval. This is most likely due to the sinking of a shaft which was completed in November 2017. The map also shows that parts of the proposed HS2 route go through some of the most dynamic areas of coal mining subsidence in England.
UK ground motion map
Coal mining areas contain large regions of surface rebound (uplift – blue on the map) which is a common occurrence as the underground workings flood after closure, but there are also many instances of collapsing mines deep underground that may still lead to surface subsidence (red/brown on the map) decades after closure. The examples of such effects can be seen extensively over former coalfields such as Leigh, Greater Manchester; North Nottinghamshire; South Yorkshire; Stoke-on-Trent; and Midlothian. Even though the map shows ground movement in these and other areas, there is very little cause for concern, as the rates are typically very low (only a few millimetres per year) and would be barely noticeable in most cases.
The map identifies subsiding areas (in red/brown) in Scotland’s Flow Country, the largest blanket bog in Europe and the largest single terrestrial carbon store in the UK, so ensuring that the extent of the damage can be assessed. This information can contribute towards international reports on emissions which are submitted to the United Nations Framework Convention on Climate Change (UNFCC), the Kyoto Protocol and the European Union. It also provides useful evidence on the success of restoration campaigns which are important for reporting on carbon sequestration.