Title: Restoring tidal wetlands in the upper estuary
Lead Supervisor: Dr Jonathan Dale, Department of Geography and Environmental Science, University of Reading
Email: j.j.dale@reading.ac.uk
Co-supervisors: Dr Jess Neumann, Department of Geography and Environmental Science, University of Reading; Dr Sally Little, Nottingham Trent University; Dr Olly van Biervliet
UKRI funding only covers Home fees which increase annually. International students may still apply to this project, but will be required to meet the difference between the International and Home student fees themselves.
Upper estuarine tidal marshes form at the top of estuaries, where tidal freshwater and low-salinity waters meet the non-tidal freshwater river. These habitats are now rare in the UK due to centuries of land claim, yet they provide vital ecosystem services including carbon storage (Verhoeven, 2014). For example, it has been recognised that upper estuarine habitats have a larger atmospheric carbon storage potential than lower estuarine ecosystems such as saltmarsh (Adame et al., 2024). Despite their importance, they remain poorly understood, complicating efforts to assess their vulnerability to human activity and climate change.
An emerging priority area for estuarine management is estuarine squeeze, which describes the loss of upper estuarine tidal freshwater and low salinity zones due to increasing salinities. This occurs when in-channel barriers (e.g. weirs and sluices) prevent the landward migration of the estuary in response to sea-level rise and/or reduced river flows, allowing saltwater to intrude further upstream and ‘squeeze’ out the upper estuary (Little et al., 2022; Pietkiewicz et al., 2025). Tidal marsh restoration methods, such as managed realignment, provide an opportunity to (re)create upper estuarine habitats, whilst also providing a more sustainable approach to flood defence (e.g. Temmerman et al., 2013). However, the understanding of the development and evolution of restored upper estuarine tidal marsh is derived from sites where tidal inundation is controlled using sluices and tidal gates to ensure the delivery of targeted habitat types (Van Putte et al., 2025). Data on other methods of tidal marsh restoration do exist, but for the open coast and in the mid to lower estuarine zones (e.g. Dale et al., 2019; Mossman et al., 2022) where the salinity and sediment availability is typically higher.
This project will address these knowledge gaps by determining the factors influencing the development of upper estuarine restoration schemes without artificial structures controlling tidal inundation, providing an important new insight into site development without continued management governing site evolution. This will be achieved through a combination of interdisciplinary field and laboratory, earth observation, and geospatial analysis. Measurements of the hydrodynamics (water depth, current velocity, salinity), sediment availability, and marsh properties including carbon stock, redox potential, habitat type and biomass will be taken from restored sites of differing ages, tidal ranges, and freshwater inputs. Measurements will also be taken at neighbouring pre-existing reference sites to contextualise findings and used to determine the current functioning of the restored sites.
The understanding of site functioning will be applied to multispectral satellite and new high resolution uncrewed aerial vehicle multispectral and elevation measurements. From these datasets, the spatial and temporal variations in site functioning will be evaluated to assess how hydrological, morphological and biological processes contribute towards site evolution. This will include evaluating the parameters influencing site development and vegetation establishment, such as channel evolution, changes in elevation, water depth and current velocity, and quantifying temporal variations in site functioning.
Geospatial modelling of potential future restoration sites will then be conducted, based on the empirical datasets generated during the project, to critically assess the locations and requirements for future upper marsh restoration alongside the potential human-imposed constraints. Sites will be categorised according to their suitability for restoration using a systematic criteria approach, providing a novel assessment of the opportunities to protect and restore upper estuarine and transitional habitats in response to climate change. Modelling estuary-scale implications in terms of sediment transport and water levels could also be considered, depending on the student’s ability and interests.
The student will work in partnership with stakeholders leading the restoration of estuarine habitats, including WWT and the Environment Agency. Findings will provide guiding principles for upper estuarine tidal marsh restoration strategies, based on the site characteristics, by critically appraising the ability, benefits, and implications of restoration in the upper estuary. In doing so, the project will provide coastal managers with the ability to make informed decisions regarding future site design based on the environmental conditions and the requirements of the scheme.
Training opportunities:
There will be training in fieldwork, laboratory work and remote sensing depending on the student’s individual needs. A placement will be offered with WWT, who are a large, multi-disciplinary team of scientists working on large-scale restoration projects. Findings will be shared with the Environment Agency to inform their on-going restoration initiatives. The student will be encouraged to apply for funding to complete a GVC Uncrewed Aerial Systems pilot license. The supervisory team will support the student’s engagement in events taking place at the University of Reading and beyond to enable integration into the wider research community.
Student profile:
This project would be suitable for students with a degree in Geography or Environmental Science or a closely related environmental, ecological, oceanographic or physical science. A range of methods and approaches will be used during the study, and it is not expected that the candidate will have expertise in all areas. It is intended that the student will undertake fieldwork in muddy intertidal environments to conduct essential sampling, although if required necessary adjustments including the secondary data options will be considered. The student should also have experience, or a willingness to learn, laboratory and remote sensing skills. UKRI funding only covers Home fees which increase annually. International students may still apply to this project, but will be required to meet the difference between the International and Home student fees themselves.
Co-Sponsorship details:
The project will receive co-sponsorship from the Wildfowl and Wetlands Trust. This will be in the form of a placement and collaborative visits.
References:
- Adame, M. F., Kelleway, J., Krauss, K. W., Lovelock, C. E., Adams, J. B., Trevathan-Tackett, S. M., Noe, G., Jeffrey, L., Ronan, M., Zann, M., Carnell, P. E., Iram, N., Maher, D. T., Murdiyarso, D., Sasmito, S., Tran, D. B., Dargusch, P., Kauffman, J. B., & Brophy, L. (2024). All tidal wetlands are blue carbon ecosystems. BioScience, 74, 253–268.
- Dale, J., Cundy, A. B., Spencer, K. L., Carr, S. J., Croudace, I. W., Burgess, H. M., & Nash, D. J. (2019). Sediment structure and physicochemical changes following tidal inundation at a large open coast managed realignment site.Science of the Total Environment, 660, 1419–1432.
- Little, S., Lewis, J. P., & Pietkiewicz, H. (2022). Defining estuarine squeeze: The loss of upper estuarine transitional zones against in-channel barriers through saline intrusion. Estuarine, Coastal and Shelf Science, 278, 108107.
- Mossman, H. L., Pontee, N., Born, K., Hill, C., Lawrence, P. J., Rae, S., Scott, J., Serato, B., Sparkes, R. B., Sullivan, M. J. P., & Dunk, R. M. (2022). Rapid carbon accumulation at a saltmarsh restored by managed realignment exceeded carbon emitted in direct site construction. PLOS ONE, 17, e0259033.
- Pietkiewicz, H., Mortimer, R. J. G., Hirst, A. G., Lewis, J. P., Clarke, L., & Little, S. (2025). Artificial barriers and estuarine squeeze: A novel assessment of estuarine vulnerability to climate change and sea level rise. Estuarine, Coastal and Shelf Science, 320, 109299.
- Temmerman, S., Meire, P., Bouma, T. J., Herman, P. M. J., Ysebaert, T., & De Vriend, H. J. (2013). Ecosystem-based coastal defence in the face of global change. Nature, 504, 79–83.
- Van Putte, N., Temmerman, S., Seuntjens, P., Verreydt, G., De Kleyn, T., Van Pelt, D., & Meire, P. (2025). Historical soil compaction impairs biogeochemical cycling in restored tidal marshes through reduced groundwater dynamics. Science of the Total Environment, 958, 178001.
- Verhoeven, J. T. A. (2014). Wetlands in Europe: Perspectives for restoration of a lost paradise. Ecological Engineering, 66, 6–9.
