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All sites comprise a gravel barrier, which sits on a sandy beach platform. These barriers provide natural protection from storm surge and storm waves. Thus their vulnerability is coupled to their geomorphic evolution and how it responds to changing storm intensities, which needs to be assessed over time scales (seasonal to decadal) for effective management planning. The defence provided by these natural barriers is important for the transport network (road and rail), the ecology and the future viability of economic development within the study areas. The chosen sites are data rich and represent different coastal orientations to enable site comparison, while also providing a range of conditions for assessing the capability of the newly developed model.
Model Development and Data
To assess the future resilience of these managed shorelines in a changing climate a coastal evolution model that is robust for sandy coasts (Barkwith et al., 2014) will be developed to include a gravel transport formulation. Research has recently focused on simulating overwash and infiltration of gravel barriers in relation to flood risk (McCall et al., 2014). Event-driven overwash is important in maintaining barrier width (Lazarus and Armstrong, 2015) and will be represented in the long-term evolution. This research will assess the evolution of gravel barriers and how this impacts the long-term flood risk. Case studies with available bathymetric and wave data will enable model development and testing, to ensure the new approach is robust in varied wave conditions. The model employed is chosen due to its capability in simulating long-term shoreline evolution in response to the prevailing wave climate with consideration of human intervention (Barkwith et al., 2014, e.g. Fig. 1). The new model will be setup and calibrated against historic data for the known trends in shoreline recession. Once validated, it will be used to explore barrier sensitivity to changing wave climates and the impact of a variety of management options. A cost-benefit analysis will require working with the local authorities to understand the cost of nourishment schemes in present day values and to determine the increase in resilience generated by different options.
In the year 1 the student will visit the local authorities at each site to gain an understanding of the management issues and the local conditions. Long-term shoreline monitoring will be available through the UK wave buoy network and the Cardigan Bay Coastal Group, beach and LiDAR surveys, photography and sediment sampling. These data will inform model setup and calibration against historic trends in shoreline evolution in response to the wave record. The student will explore existing formulations for gravel transport, prior to incorporating the most suitable approach within the model. Genetic programming (Limber & Murray, 2014) will also be considered to improve the representation of nearshore wave transformation.
In year 2 the research will concentrate on model development and application. The model will be developed at the most data rich site and tested at the other sites to ensure it is transferable to other gravel barrier locations. Once able to simulate historic trends at all sites the model will be used to project plausible future shoreline positions in response to scenario future wave climates and management strategies, these may include ‘Do nothing’ or ‘Artificial nourishment to hold the line’. It will also be used to assess the importance of considering wave conditions coincidental with high water relative to the full wave climate.
Towards the end of year 2 and at the start of year 3 the model will be applied to assess the vulnerability and plausible evolution of the barrier at all sites under different wave and management scenarios in combination with a cost-benefit analysis. The latter part of the third year will be devoted to writing the thesis.
This PhD will sit within a collaborative partnership of academics, consultants and coastal authorities. Although hosted by the Institute of Sustainable Coastal Oceans at Liverpool, the student will spend time at BGS training in the application of the CEM; at PU to gain experience in beach surveys and knowledge about gravel barrier processes; and with Royal Haskoning DHV to experience consultancy, while also providing training for commercial application of the newly developed code. Annual meetings with members of the Cardigan Bay Coastal Group will enable access to data, and learning about the site specific coastal processes and management issues, focusing this research to support management strategies.
Competitive tuition fee, research costs and stipend (£14,056 tax free) from the NERC Doctoral Training Partnership “Understanding the Earth, Atmosphere and Ocean” (website: http://www.liv.ac.uk/studentships-earth-atmosphere-ocean/) led by the University of Liverpool, the National Oceanographic Centre and the University of Manchester. The studentship is granted for a period of 42 months. Further details on eligibility, how to apply, deadlines for applications and interview dates can be found on the website. EU students are eligible for a fee-only award. Note that this is a CASE project with strong interactions with industrial partner. The successful candidate will benefit from an extra £1,000.-/year (Tax free).
Barkwith, A., Hurst, M. D., Thomas, C. W., Ellis, M. A., Limber, P. L., and Murray, A. B. (2014) Coastal vulnerability of a pinned, soft-cliff coastline, II: assessing the influence of sea walls on future morphology, Earth Surf. Dynam., 2, 233-242.
McCall, R.T., Masselink, G., Poate, T.G., Roelvink, J.A., and Almeida, L.P. (2015) Modelling the morphodynamics of gravel beaches during storms with XBeach-G, Coastal Engineering, 103, 52-66.
Knight, P. J., Prime, T., Brown, J. M., Morrissey, K., and Plater, A. J. (2015) Application of flood risk modelling in a web-based geospatial decision support tool for coastal adaptation to climate change, Nat. Hazards Earth Syst. Sci., 15, 1457-1471.
Lazarus, E. D. & Armstrong, S. Self-organized pattern formation in coastal barrier washover deposits. Geology 43, 363-366, doi:10.1130/g36329.1 (2015).
Limber, P. W., A. Brad Murray, P. N. Adams, and E. B. Goldstein (2014), Unraveling the dynamics that scale cross-shore headland relief on rocky coastlines: 1. Model development, J. Geophys. Res. Earth Surf., 119, 854–873, doi:10.1002/2013JF002950.
Phelps, J.J.C., Brown, J.M., Plater, A.J., Barkwith, A., Hurst, M.D., and Ellis, M.A.. (2015) Modelling coastal erosion and sediment transport on the Dungeness Foreland, UK. Southampton, National Oceanography Centre, 30pp. (National Oceanography Centre Research and Consultancy Report, 48), http://nora.nerc.ac.uk/511382/