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Redefining Coastal Squeeze: A Report for the Environment Agency

The team’s research provides an improved understanding of the process of coastal squeeze and has developed standardized methods to assess it.

Jacobs Global Technology Director - Coastal Planning & Engineering Professor Nigel Pontee recently led the production of a report for the UK Environment Agency which will inform future assessment of coastal squeeze and the requirement for the creation of compensatory habitat.

The work involved several colleagues within Jacobs as well as key contributions from Kenneth Pye Associates Ltd., and was commissioned by the Joint Flood and Coastal Erosion Risk Management Research and Development programme, part of  Environment AgencyDepartment for Environment, Food & Rural AffairsWelsh Government, and Natural Resources Wales.  This project arose from numerous studies for the Environment Agency over the past decade in addition to a series of technical papers that challenged a widely accepted paradigm and identified areas where further work was required.

What is coastal squeeze?

In the U.K., large areas of coastal habitats have been lost due to progressive phases of land claim over the past 2,000 years. Although losses due to large scale land claim have been much lower over the past 40 years, significant concerns remain about the indirect losses of coastal habitats caused by the presence of coastal defenses and rising sea levels. The term coastal squeeze is commonly used to describe this process, and it is a key driver for creating compensatory habitats.

In the past the ways that coastal squeeze has been defined and assessed around the U.K. have varied. In some places all habitat losses have been assumed to be as a result of coastal squeeze, where in fact the losses may be due other causes.

Report findings

Developed over a 2-year period, first and foremost, the report provided a more precise definition of the term ‘coastal squeeze’ for use throughout the U.K.:  “….the loss of natural habitats or deterioration of their quality arising from anthropogenic structures or actions, preventing the landward transgression of those habitats that would otherwise naturally occur in response to sea level rise in conjunction with other coastal processes. Coastal squeeze affects habitat on the seaward side of existing structures.” The full report carefully explains each of the terms within the definition.

The revised definition differs from some previous definitions by including a number of additional elements: a wider range of habitats and structures, additional management activities, erosion caused by expansion of saltmarsh channels, and aspects of habitat quality.

The work also produced:

  • A standard method and guidance for consistently assessing coastal squeeze.
  • Four case studies that demonstrate how the method can be applied to mudflats, saltmarshes and sand/shingle beaches.

The work demonstrated that historic coastal squeeze losses may have been smaller than previous assessments have suggested since some of the losses may have been due to other causes. The report recommended that in the future, the assessment of coastal squeeze needs to more carefully consider the various possible causes for habitat loss. The report also noted that in the future, coastal squeeze could become more widespread due to accelerated sea-level rise.

Collaboration at its best

The report was developed in collaboration with numerous organizations across England and Wales including the Environment Agency, Natural England, and Natural Resources Wales. The project was steered by a group of 13 members from the Environment Agency, Defra, Natural England, Scottish Environment Protection Agency, Marine Management Organisation, Natural Resources Wales and Welsh Government.

Thanks to the professional and open discussion via many discussion meetings with the Project Board, the team successfully reached a consensus on various aspects of the work, especially the definition itself and the conclusions

““The concept of coastal squeeze is very well established within U.K. However, previous definitions and assessment methodologies have varied and have not always considered all of the causes for coastal habitat loss,” Jacobs Project Leader Professor Nigel Pontee shares. “Working with a small team of experts we were able to clearly explain the various causes for habitat loss, set out a precise definition and assessment method to improve future assessments. On this project the large number of organizations with different perspectives and knowledge provided an excellent learning opportunity for our team.”

Flood & Coast Excellence Awards Shortlist

Judges from the Flood & Coast Excellence Awards for 2021 shortlisted the report for an award. These prestigious awards are a long-standing way to recognize the important work done in the previous year that has contributed to managing flood and coastal risk, building local flood resilience and taking action on climate change.

Chrissy Mitchell, project manager for the project at the Environment Agency adds, “This was a very important project for the Environment Agency. The impacts of this project are far reaching and go far beyond the Agency. It is relevant to all four U.K. nations and impacting upon the work of numerous organizations, plans and projects, including the Environment Agency, Defra, Welsh Government, Natural England, and National Resources Wales among others.”

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Want to read more about coastal squeeze? Check out the report and more below:

General Information and Summary Video:

https://www.gov.uk/flood-and-coastal-erosion-risk-management-research-reports/what-is-coastal-squeeze

Documents:

What is coastal squeeze? - summary (198KB) PDF

What is coastal squeeze? - technical report (15MB) PDF

 

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