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C421: Building with Nature: the role of bio-physical linkages within coastal wetland restoration (Priority project with CASE partner) (Lead Supervisor: Iris Möller, Geography)

Supervisors: Iris Möller (Geography) and Tom Spencer (Geography

Importance of the area of research:

The restoration of intertidal coastal habitat has been highlighted as a key necessity by the UK Committee on Climate Change's Adaptation Sub-Committee ‘Managing the Land in a Changing Climate' report of 2013. Without such restoration, critical habitats for the maintenance of important ecosystem services are at risk of being lost (around 105,000 ha of coastal habitat have been identified as providing natural coastal protection from flooding and erosion around the coastline of England, alongside carbon storage, biodiversity and health and well-being benefits). Such loss would add to the 20% decline (from 62,000 ha in 1945 to 49,000 ha in 2010) already observed.

To achieve this aim, a better understanding is necessary of how bio-physical process linkages between the above-ground plant structures, below-ground sediment structures, and hydrodynamic forcing factors operate. In particular, knowledge of process thresholds, such as the onset of erosion under increasing wave action and/or increasing magnitude / duration of tidal currents are required to feed into existing intertidal marsh evolution models. Currently, such models are based on largely linear relationships.

Project summary:

This project will address bio-physical interactions that control transitions from depositional to erosive process regimes, i.e. when hydrodynamic energy thresholds become exceeded such that hydrodynamic forcing leads to the initiation of erosion of cohesive coastal sediments in and around biological structures, such as salt marsh plants and crab burrows. Following on from a large scale wave exposure experiment to be conducted in the large wave flume facility in Hannover, Germany in the summer of 2018, the project will build on this study through conducting a series of smaller scale flume experiments in the laboratory in Cambridge. The relative importance of sediment characteristics and type of UK salt marsh plant species on the erosion thresholds under a range of tidal flow velocities within a salt-water flume will be investigated and used to improve existing morphodynamic models.

What the student will do:

The student will analyse data on wave-erosion thresholds derived from the Hydralab+ project for a range of salt marsh vegetation configurations and in extreme hydrodynamic conditions. The student's project will then focus in more detail on the role of varying marsh sediments and plant species as collected from a range of UK East, West, and South coast salt marsh sites, alongside sites where managed realignment has led to coastal wetland restoration. Marsh surface samples collected from within the seasonally vegetated marsh zone with intact individual plants and root base will be exposed to a range of tidal currents within the Department of Geography's flume. Plant-sediment interactions will be closely observed and sediment dynamics recorded through the use of high-precision repeat digital photogrammetry and the deployment of surface sediment traps. Flume data may be supplemented through field observations (the deployment of sediment traps and repeat close-up surface topography photogrammetry alongside hydrodynamic measurements).

Please contact the lead supervisor directly for further information relating to what the successful applicant will be expected to do, training to be provided, and any specific educational background requirements.

References:

Möller, I., Kudella, M., Rupprecht, F., Spencer, T., Paul, M., van;Wesenbeeck, B. K., ... Schimmels, S. (2014). Wave attenuation over coastal;salt marshes under storm surge conditions. NATURE GEOSCIENCE, 7(10),;727-731. http://doi.org/10.1038/NGEO2251

Spencer, T., Möller, I., Rupprecht, F., Bouma, T. J., van Wesenbeeck, B. K.,
Kudella, M., ... Schimmels, S. (2016). Salt marsh surface survives
true-to-scale simulated storm surges. Earth Surface Processes and Landforms,
41(4), 543-552. http://doi.org/10.1002/esp.3867

Friess, D. a, Krauss, K. W., Horstman, E. M., Balke, T., Bouma, T. J.,
Galli, D., & Webb, E. L. (2012). Are all intertidal wetlands naturally
created equal? Bottlenecks, thresholds and knowledge gaps to mangrove and
saltmarsh ecosystems. Biological Reviews of the Cambridge Philosophical
Society, 87(2), 346-66. http://doi.org/10.1111/j.1469-185X.2011.00198.x

Follow this link to find out about applying for this project.

Other projects available from the Lead Supervisor can be viewed here.

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