Waves hitting the coastline of Westward Ho!

Project context

The #gravelbeach project is funded by a £3m Natural Environment Research Council (NERC) Special Highlight Topic grant and is led by Dr Jenny Brown of NOC Southampton, involving a consortium of academic and non-academic partners, with researchers from the Coastal Processes Research Group playing a key role. 
This NERC Special Highlight Topic was originally proposed in 2021 by Professor Gerd Masselink (Topic F: ‘Building understanding of natural coastal protection by gravel barriers in a changing climate’), which addresses the following six research questions:
  1. How do decadal scale morphodynamics of gravel barriers respond to changes in sea level, storminess and sediment supply, and influence coastal evolution? How will this impact on the ecosystems they support? 
  2. Under future climate change, will the coastal protection role of gravel barriers be compromised, potentially triggering management interventions?
  3. When and how does sediment transport on gravel barriers differ from the better studied sand cases? 
  4. What is the internal structure and composition of gravel beaches, and how do variations in composition influence beach morphology and dynamics? 
  5. What is the role of hydraulic conductivity in influencing barrier behaviour? 
  6. Can we quantify the critical interactions between gravel barriers and the back-barrier environment (marsh, lagoon, estuary), as well as the interplay between gravel barriers and coastal structures? 


It is generally accepted that gravel barrier shorelines offer widespread, critically important natural flood protection to many coastal communities. Moreover, their creation and enhancement are increasingly seen as sustainable and nature-based adaptation options that boost natural capital. But these assets must be well managed to ensure they continue serving such functions in the face of increased risk of coastal erosion and flooding. Our understanding and modelling capability of gravel beach and barrier dynamics significantly lags behind that of their sandy counterparts.
The principal aim of #gravelbeach is therefore to enhance understanding of gravel barrier systems and improve predictive capability to support more sustainable coastal management, increase overall coastal zone resilience and reduce vulnerability to climate change.
Aerial view of the coastline at Torcross

The Frame of Reference for #gravelbeach

A Frame of Reference approach was used to design and structure this project.


  • Classify and characterise all UK gravel barriers 
  • Analysis of gravel barrier topography and shorelines over annual to decadal time scale
  • Observe barrier stratigraphy through sediment sampling, coring and ground-penetrating radar
  • 'Storm chasing' on six gravel barrier sites to collect morphodynamic data under extreme conditions 
  • Physical laboratory experiments to study fundamental sediment transport processes 
  • Develop, validate and calibrate numerical models of gravel barrier morphodynamics over range of time scales 
  • Apply new numerical models to inform management at several sentinel gravel barrier sites 
  • workshop for practitioners and project partners 
  • Training of post-docs and PhD's 


  • Database of all UK gravel barrier sites 
  • Contextualisation of gravel barrier morphodynamics and sediment stratigraphy
  • New sand-gravel sediment transport equation
  • Numerical modelling capability for gravel barrier morphodynamics over multiple scales 
  • Peer-reviewed publications 
  • Conference presentations 
  • Unique hydro- and morphodynamic data sets from the field and laboratory for future model development 
  • Predictions of future coastal dynamics for several sentinel gravel barrier sites and evaluation of adaptation strategies 
  • Skill enhancement amongst researcher staff and trained PhD students 

Over-arching aim

To deliver enhanced understanding and modelling capability of gravel barrier systems to support more sustainable coastal management, increasing coastal resilience and reducing vulnerability to climate change.

Over-arching objective

Deep understanding of the complex interplay between sediments, morphology, hydrodynamics and groundwater dynamics in gravel barrier systems. 


  • Improved understanding and modelling capability of how gravel barriers respond to changing sea level, storminess and sediment supply (Q1) 
  • Evaluation of how natural protection by gravel barriers will be compromised by climate change, potentially triggering management interventions (Q2) 
  • Quantitative consideration of the unique aspects of sediment transport of sand-gravel mixture and how this influences barrier morphodynamics (Q3) 
  • Characterisation of the internal structure and spatial variability in sediment composition, and how this impacts on gravel barrier morphodynamics (Q4)
  • Insight into the role of hydraulic conductivity in influencing barrier behaviour (Q5) 
  • Appreciation of the fundamental difference between constructive overtopping and destructive overwash, and how this influences the back-barrier (Q6) 
The activities, outputs and outcomes outlined above will go through a process of iterative refinement throughout the project. 

Gravel beaches and barriers

Beach and barrier systems with a dominant gravel fraction, including ‘pure’, ‘compound’ and ‘mixed sand-gravel’ systems (hereafter collectively referred to as ‘gravel barriers’), are common in the UK and throughout the world. 
Gravel barriers extend along a fifth of the non-estuarine coastline of England and Wales, and are also common in Scotland and Northern Ireland. At many locations they act as natural coastal defences and are unique ecosystems, especially in association with back-barrier marsh or lagoonal systems. In offering physical protection from coastal flooding and erosion, they represent critical natural capital. For example, over 30 coastal frontages (> 180 km) in SE England have a mixed sand-gravel barrier as the main coastal defence. 
Acknowledging the socioeconomic value of gravel barriers, significant sums are spent annually on engineering structures and management practices to maintain and enhance their capacity for coastal protection. Gravel barriers also represent valuable morpho-sedimentary niches, supporting internationally important biodiversity (e.g., ‘vegetated shingle’) and providing back-barrier conditions that enable carbon storage. Yet, given the vital functions played by gravel barrier systems, our understanding of their resilience to climate change is alarmingly poor.
Gravel barrier, beachfront
Man conducting gravel survey on a beachfront
Gravel beach cliff


The over-arching aim is underpinned by five Work Package objectives: 
(1) develop a GB-wide gravel barrier typology encompassing morpho-sedimentary structure and dynamics; (2) collect and analyse field data of event-scale gravel barrier dynamics; (3) collect and analyse laboratory data, and derive new equations for key processes; (4) develop new predictive capability for gravel barrier dynamics over short- to long-term time scales, accounting for cross-shore and longshore sediment transport; and (5) apply new understanding and enhanced numerical capability to project future dynamics of gravel barriers. 
Graphic showing the increased chance of back-barrier change
All work packages involve use and implementation of innovative measurement, analysis and modelling methods and tools: use of AI for sediment size analysis; installation of LiDAR towers for recording waves, runup and beach change; deployment of UAV and USVs for topographic and bathymetric surveys; storm surveys; state-of-the art physical modelling of mixed sand-gravel sediment transport modelling; and novel equilibrium-based numerical modelling of gravel barrier dynamics. 
Involvement of an Impact Advisory Board at the outset ensures that the new science and tools emanating from this project will find application in the real world. 
An international Scientific Advisory Board will enable inclusion of expertise from outside UK, as well as facilitating international reach of the research impacts.
Chesil beach, Dorset, pictured with a calm coastline
Men carrying out research at Loe Bar beach, Cornwall
Unmanned vehicle on the water
Chesil beach, Dorset, pictured during a storm with a rough, wavey coastline


Starting in January 2024, this four-year project is divided into two distinct phases: Years 1–3 for data collection/analysis and numerical code development; and Year 4 for application of understanding and predictive tools. 
The four milestones are: 
: end of March 2024;
b: end of September 2025
PDRAs in position
End of December 2025
Completion of all collection and analysis of field, physical and secondary data
End of December 2026
Numerical code finalised, ready for centennial application
End of September 2027
End of project
Frequent online and in-person meetings will be held, including annual meetings with the complete research team and (Science and Impact) Advisory Boards, separate annual Advisory Board meetings and quarterly WP meetings.

Academic and technical staff