CR2025_14 Hydro-Ecological-Sediment feedbacks for improving coastal wetland Restoration (HES-Res)

Lead Supervisor: Harshinie Karunarathna, Department of Civil Engineering, Swansea University

Email: h.u.karunarathna@swansea.ac.uk

Co-supervisors: Cai Ladd, Department of Geography, Swansea University; William Bennett, Department of Civil Engineering, Swansea University; Jonathan Dale, Department of Geography and Environmental Science, University of Reading

Coastal wetland (seagrass, saltmarsh, and mangrove) restoration directly addresses climate change adaptation agendas, builds towards the United Nations’s Decade on Ecosystem Restoration programme, and tackles three United Nations Sustainable Development Goals (Climate Action; Good Health and Wellbeing; Sustainable Cities and Communities) by delivering coastal flood protection, carbon capture, and ecosystem, health and wellbeing services. The UK has been at the forefront of this restoration effort, with programmes including ‘Project Seagrass’¹, ‘ReMeMarRe’², ‘Wetlands Can!’³, ‘Saltmarsh Code’⁴, and Habitat suitability modelling for seagrass in North wales⁵, all seeking to rapidly increase coastal wetland restoration efforts. The supervisory team are engaged in all these projects. This PhD project comes at an important, timely, and exciting time for coastal wetland restoration.

Complex dynamics within the interface between waves, tides, sediment, and plants (WTSP) in coastal wetland canopies is crucial for governing whether wetland restoration succeeds or fails. For example, simply planting wetland vegetation closer together can reduce wave erosion stress and improve restoration success. On the other hand, large scour holes were seen around plants in denser plant canopies which may destabilise the canopy and fail restoration efforts⁶ (Fig. 1). Therefore, a careful balance between the complex hydro-sediment environment and wetland characteristics should be maintained to achieve successful wetland restoration.

To date, research on WTSP have been largely restricted to testing plant mimics in laboratory settings^7,8. Findings (including our own⁶) show that highly complex hydrodynamics and sedimentary morphologies emerge at the WTSP that could both promote or prohibit wetland restoration. Plant-specific properties such as rigidity and stem diameter, as well as canopyscale properties such as plant density, sediment properties, and submergence levels are found to play a crucial role. Whilst these findings form a baseline for modelling WTSP for restoration efforts, the specific role of real plant morphologies in shaping WTSP dynamics remains overlooked.

Through an innovative and exiting field measurement campaign combined with computational coastal wetland modelling, this PhD project will untangle complex feedback loops in WTSP and develop a robust tool that can successfully capture them, aiming at predicting and assessing conditions amenable to successful coastal wetland restoration.

The project objectives are:

• Field-based: to measure wave/current exposure and sediment transport within wetland canopies at a selection of sites during calm and stormy conditions, using an array of Mini Buoys developed at Swansea University⁹ and other state-of-the-art sensors, and perform simultaneous drone surveys to measure topographic evolution of the study sites in high resolution;
• Computer-based: to develop a computational model linking wave/current dynamics, sediment mobility, and plant characteristics to simulate hydro-sedimentary dynamics and morphology within wetland canopies;
• Desk-based: Combine (i) and (ii) to validate and tune the model to turn it into a tool to simulate wetland interaction with the coastal hydro-sedimentary environment and explore conditions favourable for wetland restoration.

This model will be a useful tool to test and optimise potential wetland restoration options and scenarios, and help coastal managers design effective coastal wetland restoration schemes. The PhD project will fill many knowledge gaps surrounding why some restoration efforts are successful while others fail or have less success. The project will also support the selection of suitable sites for wetland restoration.

This PhD project will provide the student with a suite of skills in coastal monitoring, advanced data analysis, coastal wetland modelling, and ecosystem restoration to become a leader in coastal ecosystem restoration. The project will also provide opportunities to work with an interdisciplinary team of academics and researchers across Swansea and Reading Universities and a variety of stakeholders and prepare the student to thrive in academia or outside.

Training opportunities: 

During a 3-month placement at Welsh Coastal Monitoring Centre, the student will work with a specialist coastal monitoring team and be exposed to large-scale field measurement programme design and execution. The student will also be encouraged to engage with CROCUS, Swansea University and University of Reading training and development opportunities.  Attending relevant external events will also be encouraged, including opportunity to disseminate findings at initiatives such as the ReMeMaRe (Restoring Medows, Marshes and Reefs) Annual Conference.

Please note that BGS (Dr. Andreas Payo) has also agreed to facilitate a placement and access to their field campaigns and relevant data resources.

Student profile:

This project would be suitable for students with an undergraduate or Masters degree in Physical/Environmental Geography; Civil, Coastal, or Environmental Engineering; or a related environmental, bioscience, or physical science discipline. Willingness to learn different research techniques (field work, modelling, data analysis) and to complete fieldwork in muddy intertidal environments is essential. R, Python, Matlab or Fortan programming skills, and teamwork and excellent communication skills, will be beneficial. Reasonable adjustment to the field campaigns and project deliverables will be made according to individual student needs and backgrounds in line with our EDI principles.

Co-Sponsorship details:

The project will receive co-sponsorship from the Welsh Coastal Monitoring Centre. This will take the form of a placement.

References:

1. Project Seagrass (https://www.projectseagrass.org/)
2. ReMeMarRe (https://ecsa.international/rememare/restoring–meadow–marsh–and–reef–rememare)
3. WetlandsCan! (https://www.wwt.org.uk/wetlands–can/)
4. Saltmarsh Code  https://www.ceh.ac.uk/our–science/projects/uk–saltmarsh–code)
5. Bertelli et al. (2022) (https://doi.org/10.3389/fmars.2022.1004829)
6. Ions et al. (in review) In Journal of Geophysical Research
7. Silliman et al. (2015) https://doi.org/10.1073/pnas.1515297112
8. Keimer et al. (2024) https://doi.org/10.1002/lom3.10616 ⁹Ladd et al. (2024) https://doi.org/10.1002/lom3.10631