CR2025_17 Designing Intertidal Channels (DITCH): detecting pre-reclamation drainage channels for improved design of saltmarsh restoration schemes

Lead Supervisor: Jonathan Dale, Department of Geography and Environmental Science, University of Reading

Email: j.j.dale@reading.ac.uk

Co-supervisors: Robert Fry, Jonathan Dale, Department of Geography and Environmental Science, University of Reading; Niall Burnside, Scottish Association for Marine Sciences (SAMS); Hannah Mossman, Wildfowl and Wetlands Trust

Saltmarsh is an important coastal habitat that provides a range of ecosystem services including carbon storage, flood defence through wave attenuation, nursery grounds for commercial fish species and improvements to water quality. However, historic land claim for agriculture, coupled with sea level rise, has resulted in huge global losses of this habitat. The need to restore saltmarsh habitat to compensate for these losses is becoming a major priority for coastal managers. For example, the Environment Agency are targeting a 15% increase in saltmarsh over the next 20 years and WWT aims for 25,000 ha of restored habitat by 2050. These targets, coupled with the development of a Saltmarsh Code to finance saltmarsh restoration¹, means ensuring the successful design and implementation of saltmarsh restoration is becoming of increasing importance. One of the most common methods of restoring saltmarsh habitat is managed realignment (MR), where coastal flood defences are breached allowing tidal inundation of low-lying coastal land, often in areas that have previously been reclaimed for agriculture. New saltmarsh then colonises and develops within the MR site.

A key factor in determining the development of new saltmarsh, and ultimately the success of the MR site, is the morphology and topography of the site. Creeks and channels play an important role in the physical and ecological functioning of saltmarsh, acting as a conduit between the marsh and the wider estuary for water, sediment, seeds, carbon and nutrients. These features also provide habitats for fish and help to facilitate drainage.

The design of a new MR site can involve the use of pre-existing agricultural drainage networks, the excavation of new simple, linear drainage channels, or a combination of the two given the relatively high costs of channel construction. However, studies have recognised that many MR sites are morphologically closer to agricultural fields than pre-existing reference saltmarsh sites², which may impact vegetation colonisation and establishment in the MR sites. There is also evidence that creek evolution in MR sites is influence and restricted by the pre-breach morphology³, and the construction of steep banked linear channels may result in high current velocities and conditions unsuitable for many economically and ecologically important fish species⁴. Considering the requirements of all benefactors in the site design is, therefore, becoming more important. Consequently, there is a need to assess the potential of re-implementing or mirroring the pre-reclamation drainage network at future MR sites. At sites that were reclaimed for agriculture only a few decades ago this is relatively straightforward using historic maps and aerial photography. However, most sites were reclaimed hundreds of years ago, prior to these records existing, meaning it is likely to be much more challenging to reconstruct the pre-reclamation drainage networks at many sites.

This project will assess the potential of using machine learning approaches, an emerging remote sensing technique within wetland research, to identify the morphological signature of prereclamation features. Remote sensing and machine learning have previously been used in saltmarsh environments to predict the extent of vegetation communities, carbon storage and variations in soil properties. This study will innovatively develop machine learning algorithms using available topographic and multispectral satellite data, and high-resolution datasets collected using an Uncrewed Aerial System, to predict the location of pre-reclamation channels for recently reclaimed sites where historic records are available for model training and validation. Geophysical, topographic, sedimentary, and vegetation datasets will also be collected for these sites to identify the key in-situ indicators of pre-reclamation morphology. The machine learning algorithms will then be applied to potential future MR sites, such as those in the Environment Agency’s restoration potential database, where historic records do not exist, using the relevant in-situ indicators for validation.

Working in partnership with WWT, the findings from this project will inform the implementation of future MR schemes and help those involved in site design to meet saltmarsh restoration targets. Specifically, the findings from the project will be used to critically appraise the ability, the benefits, and the cost implications, of reimplementing pre-reclamation drainage networks. In doing so, the project will provide coastal managers, including WWT, and environmental consultancies with the ability to make informed decisions regarding future site design and construction based on the preexisting morphology, available budget, and the requirements of the scheme.

Training opportunities:

There will training in fieldwork, lab work and programming depending on your individual needs. A placement will be offered with WWT Conservation Evidence Team, who are a large, multidisciplinary team of scientists working on large-scale restoration projects. You will be able to visit the Scottish Association for Marine Science (SAMS) and contribute towards their marine science initiatives. You will be encouraged to apply for funding to complete a GVC license to pilot

Uncrewed Aerial Systems and to engage in events in the School and Department at the University of Reading, and beyond, to integrate 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 programming skills.

Co-Sponsorship details: 

The project will receive a CASE award from Wildfowl and Wetlands Trust.

References:

1. Mason, G.V., Wood, K.A., Jupe, L.L., Burden, A., Skov, M.W., 2022. Saltmarsh Blue Carbon in UK and NW Europe-evidence synthesis for a UK Saltmarsh Carbon Code.
2. Lawrence, P.J., Smith, G.R., Sullivan, M.J.P., Mossman, H.L., 2018. Restored saltmarshes lack the topographic diversity found in natural habitat. Ecological Engineering 115, 58-66.
3. Dale, J., Burnside, N.G., Strong, C.J., Burgess, H.M., 2020. The use of small-Unmanned Aerial Systems for high resolution analysis for intertidal wetland restoration schemes. Ecological Engineering 143, 105695.
4. Stamp, T., West, E., Colclough, S., Plenty, S., Ciotti, B., Robbins, T., Sheehan, E., 2023.
5. Suitability of compensatory saltmarsh habitat for feeding and diet of multiple estuarine fish species. Fisheries Management and Ecology 30, 44-55.