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==== Rapid Evidence Assessment ====
==== Rapid Evidence Assessment ====
As part of Work Packages 1 and 4 BGS conducted a [https://cebma.org/resources/frequently-asked-questions/what-is-a-rapid-evidence-assessment-rea Rapid Evidence Assessment](REA) to inform the six research questions.
As part of Work Packages 1 and 4 BGS conducted a [https://cebma.org/resources/frequently-asked-questions/what-is-a-rapid-evidence-assessment-rea Rapid Evidence Assessment](REA) to inform the six research questions [[https://earthwise.bgs.ac.uk/index.php/Category:Understanding_coastal_protection_by_gravel_barriers_in_a_changing_climate '''→ View Questions''']].


BGS followed the [https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/560521/Production_of_quick_scoping_reviews_and_rapid_evidence_assessments.pdf DEFRA/NERC] guidance on the production of quick scoping reviews/REAs. The UKGravelbarriers REA is based on a protocol drafted and agreed within all Work Packages and follows the PICO (Population, Intervention, Comparator, and Outcome) method by defining keywords, platforms,  and resources available.
BGS followed the [https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/560521/Production_of_quick_scoping_reviews_and_rapid_evidence_assessments.pdf DEFRA/NERC] guidance on the production of quick scoping reviews/REAs. The UKGravelbarriers REA is based on a protocol drafted and agreed within all Work Packages and follows the PICO (Population, Intervention, Comparator, and Outcome) method by defining keywords, platforms,  and resources available.

Latest revision as of 15:58, 5 September 2025

Team

This research project is possible thanks to the close collaboration between researchers from the British Geological Survey (BGS), UK Centre for Ecology and Hydrology (UKCEH), and the University of Nottingham (UoN), coastal engineering practitioners from Kenneth Pye Associates (KPAL), Moffat and Nichol (M&N), professional Earth Observation providers from ARGANS Ltd and isardSAT, with the in kind support of professionals from the Centre for Environment Fisheries and Aquaculture (CEFAS), the Royal Society for the Protection of Birds (RSPB), the Environmental Fluid Dynamics Research Group of the University of Granada (GDFA), the Agri-Food and Biosciences Institute (AFBI), the Geological Survey of Northern Ireland (GSNI), the Wales Coastal Monitoring Centre (WCMC), and from government organisations such as Natural Resources Wales (NRW) and the Environment Agency (EA)

Research approach

Hypothesis

To answer the research questions, we have adopted two main research hypotheses.

H1: The topography and shallow-subsurface-structure of gravel barriers, including the backshore and nearshore areas control their short-term (overwash) to long-term (transgression) evolution in response to changes in sea level rise, storminess, and sediment supply.

H2: The critical interactions between gravel barriers and the back-barrier environment as well as the interplay between gravel barriers and coastal structures can be quantified from both field and numerical simulations under the assumptions of space-for-time substitution [1] and the use of appropriate complexity modelling [2].

Scope

The spatial-scope of this research will cover all gravel beaches in the United Kingdom (England, Wales, Scotland and Northern Ireland). The temporal-scope will cover their evolution over the last 20,000 thousand years (e.g. to explore both creation of gravel barrier and evolution under different sea level rise scenarios) and will explore how they might evolve in the future to 2150.

Gravel beaches types may be categorised according to the mixture of sands and gravels present, which has a significant influence on the beach slope and the more general morphological response of the beach to wave action. Three categories are defined[3][4] as pure gravel (G), mixed sand and gravel (MSG) and composite sand and gravel (CSG).

  • Pure gravel beaches have steep slopes (tan β = 0.08–0.24) and gravel extending from the storm berm to below the mean low water spring tide level.
  • MSG beaches have moderate slopes (tan β = 0.04–0.13), with sand and gravel entirely mixed both across shore and at depth.
  • CSG beaches have a steep gravel berm fronted by a low-angle intertidal terrace, with over all beach slopes of tan β = 0.05–0.14. On composite beaches, there is distinct hydrodynamic cross-shore sorting of the sand and gravel component.

Objectives

The objectives of this project are listed below, with the research questions that they address indicated;

  • O1: Review the responses of gravel barriers to the relative sea level changes observed from 20,000 years to about 100 years ago, including periods when sea levels (see Fig 1) generally rose at different rates but also remained with little change over large periods (RQ#1, RQ#4).
  • O2: Review the performance of gravel barriers over the last two decades where the Environment Agency discontinued a policy of managing sea defences by reshaping of gravel barrier profiles and we have access to more detailed observations (RQ#1).
  • O3: Collect new field data to improve our understanding of sediment transport on gravel barriers, their shallow subsurface structure and effects of hydraulic conductivity on storm (individual) and decadal evolution (RQ#3, #5).
  • O4: Develop a broad-scale simulator of the evolution of a selected coastal barrier and backshore habitat, that account for changes in climate change, sediment supply and management interventions extending to 2150 (RQ#2, #5, #6).
  • O5: Quantify the critical interactions between gravel barriers and the back-barrier environment as well as the interplay between gravel barriers and coastal structures in representative field studies (RQ#2, RQ#6).
  • O6: Curate the data and models produced in this project beyond the lifetime of the project to enable further research and support decision making.

Program of work

To deliver the project objectives we have organised the work in five work packages:

Diagram showing program of work of GBcoast project.

WP 0 is where all the activities related with project management and coordination are integrated. This includes one in person meeting per year with all project partners and embedded practitioners that will act as project steering group and expert group providing data, access to networks and know-how. The main activities, milestones and deliverables of the WP1 to WP4 are summarised in the table below.

Fundamental to our approach is that:

  1. Successful prediction of long-term barrier behaviour requires broad representation of the coastal systems of which they are a single part, and that,
  2. Modelling capability is improved in terms of prediction and relevance to coastal management decision making by integrating the expertise of successful and established practitioners in coastal geomorphology with numerical modellers of coastal processes.

Overall, through system analysis and numerical modelling, based on four work packages, we will map and quantify gravel barrier responses to individual, ‘violent’, events such as storms in the context of longer-term ‘progressive’ impacts such as sea level rise, changes in sediment sources, and human interventions. New process understanding will be achieved by seamlessly combining innovative field observational approaches of surface and subsurface processes with advanced numerical modelling. The long-term numerical simulations will be based on predicted scenarios of sea level rise, increased wave heights and changes in coastal orientation based on UKCP18 and other recent climate change studies. The results will support improved and sustainable coastal management based on the improved understanding of how gravel barriers evolve over longer time scales under different climate conditions and human intervention scenarios. They will be a significant advance from the new comprehensive and novel, multi-scale observations of key processes that drive long-term gravel beach morphodynamic evolution.

Work Package Activities Milestones Deliverables

WP1: Spatial distribution and temporal evolution of UK gravel barriers and their back barrier ecosystems.

  • Creation of UK gravel barrier and back barrier environments research database
  • Apply state-of-the-art statistical methods to quantify joint and spatially coherent probabilities
  • Optimisation of machine learning to quantify habitat structure and extent
  • 1st sprint on geospatial platform development (Q1 2024)
  • End of collecting management intervention data from local authorities (Q3 2024)
  • Fast-track of statistical analysis for selected case studies (Q4 2024)
  • Characterization of historical met-ocean drivers and topographical and shoreline metrics of change (Q1 2025)
  • Geospatial platform on current and future gravel barrier habitat extent (Q4 2024)

WP2: Field data collection at selected case study sites

  • Expanding satellite derived shoreline proxies in time and space
  • Use DIST to create a unique field dataset of longshore sediment transport
  • Characterisation of gravel barriers and broader context structure
  • Field assessment and biophysical relationships between gravel barriers and vegetation
  • Update requirements to produce satellite MSI and SAR historical shoreline database that will be used in this project (Q1 2024)
  • Planning and equipment acquisition and risk assessment for alongshore sediment transport campaigns (Q2 2024)
  • Planning and equipment acquisition and risk assessment for in the field hydraulic conductivity surveys (Q2 2024)
  • Quantification of biophysical and landscape characteristics (Q4 2026)
  • Extended database for Northern Ireland of 38 years of historical MSI WL and MSL tideline (Q4 2024)
  • New database of historical SAR derived shorelines for designated case studies (Q4 2024)
  • Database of alongshore sediment transport, hydrodynamic and structure (Q3 2025)
  • Database of hydraulic conductivity before, during and after storms for selected case studies (Q4 2025)

WP3: Development of a broad-scale gravel barrier simulator

  • The Coastal Modelling Environment (CoastalME) will be used to represent the shore between Overstrand and Blakeney.
  • Explore how groundwater flooding and hydraulic conductivity affects both the backshore physic-chemical properties and drivers of change of the habitats we will use the British Groundwater Model (BGWM) developed for the Hydro-JULES research programme.
  • 3D model of the topography and superficial deposits of the study area (Q4 2024)
  • Cley Barrier groundwater simulator (Q4 2025)
  • Added groundwater module, habitats, gravel barrier module and human management interventions into CoastalME (Q4 2026)
  • Ensemble simulations of plausible future Cley Barrier in response to changes in sea level and human interventions (Q4 2026)

WP4: Quantify interactions and management intervention thresholds

  • Use the databases generated in WP1&2 and the new modelling capabilities described in WP3 to quantify the interactions and management interventions thresholds for both the Cley/Salthouse Barrier and a number of typologies representing gravel barriers around the UK.
  • Simulate the emergence and stability of barriers under variations in shoreface slope, rate of sea level rise and sedimentology.
  • Use the UKCP18, available at UK scale, and state of the art downscaling approaches and the methods used in WP1 to create an ensemble of plausible, hourly time series to force our simulations.
  • Use structural equation modelling (SEM) to build an overarching conceptual model will connect climate, geophysical and biogeographic drivers with landscape structure and ecosystem functioning.
  • Co-development of future climate and management scenarios that will be explored (Q1 2027)
  • Ensemble simulations of plausible future evolutions until 2150 using hourly time series (Q1 2027)
  • Quantification of biophysical and landscape interactions (Q4 2027)
  • Analysis on how interaction metrics might change in the future compared with historical evidence (Q4 2026);

Outcomes

Holistic understanding of the complex interactions and feedbacks between the sediment composition of the shallow subsurface, nearshore morphodynamics in response to both storms and sea level changes.

Coast erosion at Pakefield south of Lowestoft. The low cliffs along the coast here are composed of Glacial Sands and Gravels, a loosely-aggregated deposit that offers little resistance to the erosive action of the sea. An exceptionally high tide on November 30th 1936 enabled the waves to attack the cliffs on the north side of Beach Street, causing strips of cliff to fall and abandoned houses to collapse into the sea.

A new community modelling system coupled with terrestrial, marine and groundwater sectors and produce numerical simulations which can be used to support multi-hazard analyses under present and future climate change scenarios. These deliverables will be combined with an assessment of the role of coastal habitats, resulting in national maps for protective services and vulnerabilities of coastal habitats to climate-driven multi-hazards. We will also provide tools to analyse the efficacy of future coastal management schemes.

These will deliver a step change in the management of gravel coastlines in the UK.

Rapid Evidence Assessment

As part of Work Packages 1 and 4 BGS conducted a Rapid Evidence Assessment(REA) to inform the six research questions [→ View Questions].

BGS followed the DEFRA/NERC guidance on the production of quick scoping reviews/REAs. The UKGravelbarriers REA is based on a protocol drafted and agreed within all Work Packages and follows the PICO (Population, Intervention, Comparator, and Outcome) method by defining keywords, platforms, and resources available.

The evidence base of the REA firstly includes a research database of UK gravel and back barrier environments including peer-reviewed papers and grey literature (PhDs and reports). Results of the literature review are available in the following sections for each document type (paper, PhD, report) and research question. In addition, a database compiling numerous datasets from previous projects found in BGS archives, BGS websites, and other government web sites has also been made available.

Peer-reviewed papers

The papers were initially gathered following the REA protocol and predefined keywords. The method limited the search to literature available in Web of Science and Scopus, with a primary focus on the UK (Scotland, England, Wales, and Northern Ireland). These included studies conducted within the UK as well as non-UK studies led by UK-based teams or laboratories. More than 4,400 papers were identified and screened using Large Language Models (LLMs) and manual review to remove duplicates and out-of-scope papers. About 300 papers were identified as pertinent and assigned to the relevant research questions. BGS found that although interest in gravel and shingle systems has significantly increased since the 2000s, some of the research questions remain poorly studied. Research question 2 is linked to the fewest studies with only 20 in total and has only been considered since 2009. In contrast, research questions focusing on the morphological evolution of gravel and shingle systems (research question 1), their differences from more extensively studied sandy environments (research question 3), or the impacts of climate change (research question 4) have been investigated since the late 1970s and account for the highest number of studies.

Graph representing the number of studies per year for each research question

The primary focus of our literature review was limited to the UK, however, this map shows the broad geographic distribution of the studies identified by the REA worldwide.

Worldwide geographic distribution of the studies found with the REA

As expected, the UK accounts for most of the literature found (166 studies). Countries such as the USA, Canada, France, Italy, and Spain each contribute between 20 and 50 studies.

The map displays only 258 studies, even though more than 300 were identified. The “missing” studies are laboratory-, model-, or numerical-based and do not have a specific geographic location.

Grey literature

The grey literature, including PhD theses and reports, was primarily sourced using resources available to the project, such as the BGS website and archive, as well as the websites of Steering Group members (Centre for Ecology and Hydrology, Centre for Environment, Fisheries and Aquaculture Science, Kenneth Pye Associates, Moffat & Nichol, ARGANS Ltd, and the Royal Society for the Protection of Birds). Additionally, we used Google Scholar and insights from the Steering Group to complete our search. As with peer-reviewed papers, the geographical scope was limited to the UK.

PhD theses

A total of 19 (17 PhD and 2 MSc) theses were identified as relevant to the UKGravelBarriers project, but only nine of these met the REA criteria: 14 were accepted by the LLM for text screening but one was embargoed until late 2025, one was on the Canadian Arctic i.e. not UK based, and out of these just nine were based on field studies. The map below shows the distribution and locations of these nine.

Spatial distribution of UK study sites from the PhD theses identified through the REA
Reports

Across the UK, approximately 46 reports were identified and included in the literature review. However, 6 reports were unavailable for download, 5 were only available as hard copies, and 3 were too large for LLM screening. As a result, only 32 reports were ultimately considered and screened to address the different research questions.

History

This project started in response to the NERC funding opportunity called "Addressing environmental challenges: NERC highlight topics 2023" (Topic F: ‘Building understanding of natural coastal protection by gravel barriers in a changing climate’). The call was considered to be well aligned with the British Geological Survey science strategy plan 2023-2028 and in particular with the strategic priority on living with geological hazards: to mitigate and adapt to risk, we will monitor, characterise and forecast earth hazard events and their likely impacts by improving harmonisation in hazard and risk analysis, as well as focusing on hazardous climate change. The team was officially notified on the reception of this award on the 31st of January 2024 and the project started the 1st of February of 2024. Lead Grant Reference: NE/Y503265/1

Media coverage

References

  1. Muñoz López, P., Payo, A., Ellis, M.A., Criado-Aldeanueva, F. and Owen Jenkins, G., 2020. A method to extract measurable indicators of coastal cliff erosion from topographical cliff and beach profiles: Application to North Norfolk and suffolk, East England, UK. Journal of Marine Science and Engineering, 8(1), p.20. Open source paper [1].
  2. French, J., Payo, A., Murray, B., Orford, J., Eliot, M. and Cowell, P., 2016. Appropriate complexity for the prediction of coastal and estuarine geomorphic behaviour at decadal to centennial scales. Geomorphology, 256, pp.3-16. Open source paper [2].
  3. Anthony, E. J. (2008). Chapter Six Gravel Beaches and Barriers. Developments in Marine Geology. E. J. Anthony, Elsevier. Book chapter [3].
  4. CoastalWiki' Gravel Beaches Types.
The main author of this article is Andres Payo
Please note that others may also have edited the contents of this article.

Citation: Andres Payo (2025): UKGravelBarriers. Available from https://earthwise.bgs.ac.uk/UKGravelBarriers [accessed on 8-12-2025]