The most recent IPPC report on Oceans and the Cryosphere (IPCC, 2019) clearly shows sea levels will continue to rise until 2300 and (landward) retreat is one of the six recommended responses to maintain community resilience in the face of sea level rise. Around the UK, erosion risks due to climate change are accelerating and in many urban areas coastal and estuarine engineering structures are coming to the end of their design life. The land currently protected by these structures is often comprised of artificial made ground – land that was reclaimed by extending into the sea, which is often post-industrial, currently derelict or has light industrial use which is often identified by planners as suitable land for “regeneration”. This combination of low value land use and unsuitable defences gives society a choice: protect this low-lying land at increased risk with rising sea levels; or return land to the sea, in order to improve the long-term resilience of our coastal cities and towns? If we want to consider the latter option, then we urgently need more data on the composition, erosivity and rates of sediment transport of this often highly heterogeneous “made ground”. These data are required to provide an evidence base to better underpin urban coastal climate change adaptation options and restoring of the land-sea natural boundary using nature-based solutions.
Globally, we can measure, predict and model the rates of soft coast erosion and sediment transport processes and methods of assessing mixed to coarse (cobble-boulder) beach sediment dynamics are improving. This project will directly address a globally pressing and unanswered, interlinked questions: what is the sediment composition of made ground, how toxic is it and how fast does it erode and mix into the more natural coastal sediment system? Without data on the nature, erosive capacity and transport rates of former made or reclaimed urban ground, it is difficult to assess risk, to determine if it is feasible for this made ground to “retreat” by allowing erosion and coastal realignment to a more natural position. This retreat option has the potential to reduce the requirement for developing or maintaining expensive hard coastal defenses and to allow us to live more sustainably with a dynamic coast. This project will address this key knowledge gap, by carrying out pioneering research in urban geomorphology and climate change risk assessment that directly feeds into Scotland’s Dynamic Coast project & datasets, for use by practitioners.
The project’s specific objectives are to:
1) Characterise made ground using secondary data from a range of sources (e.g. local authorities, British Geological Survey) and map the distribution of made ground along the Scottish coast subject to natural erosion and associated future climate change risks (e.g. using Dynamic Coast 2 data).
2) Undertake field surveys and laboratory analyses to assess the geomorphological and sedimentological characteristics of artificial made ground. This detailed scientific work, using a range of geospatial (e.g. LIDAR, SfM) and laboratory testing methods (e.g. ICP-OES/MS to determine ecotoxic metal concentrations), to determine for selected Scottish sites: how toxic is this made ground, what is its sediment composition and volume and explore how fast does this heterogenous made ground erode and mix into the more natural coastal sediment system? Output: scientific data to underpin coastal change risk assessments and climate change adaptation planning.
3) Perform exploratory numerical modelling of sediment transport and erosion of reclaimed land/artificial made ground for a range of representative types and settings. Output: identifying key parameters in existing models that can be adapted (e.g. sediment properties) to better model urban coastal morphodynamics to improve coastal engineering and climate change adaptation decisions.
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Examples of eroding made ground mixing with natural beach sediment, Granton, Edinburgh, Scotland.