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Title: The evolution of the sediment regime in a large open coast managed realignment site : a case study of the Medmerry Managed Realignment Site, UK
Author: Dale, Jonathan
Awarding Body: University of Brighton
Current Institution: University of Brighton
Date of Award: 2018
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Coastal wetlands are of global importance, but are threatened by rising sea levels and anthropogenic activity. This thesis focuses on a method of compensating for intertidal habitat loss, known as managed realignment (MR); the process of re-locating the land/sea border by allowing inundation of the coastal hinterland. However, there is growing evidence that saltmarshes in MR sites have lower biodiversity and ecosystem service delivery than anticipated, which may have consequences for the level of coastal flood defence and ecosystem functioning. Differences in the physical sediment characteristics, structure, hydrology and geochemistry have been proposed as possible explanations for these differences, which relate to the former land use and site design. This thesis aims to evaluate how former land use, site design and construction influence the evolution of the sediment regime in managed realignment sites, using as a case study the Medmerry Managed Realignment Site, West Sussex, United Kingdom, the largest open coast MR site in Europe (at the time of site inundation). A novel combination of surface sediment, hydrodynamic, creek morphogenesis, and subsurface structure and physiochemical datasets are analysed from a two year monitoring period. Results indicate that sediment was mainly imported into the Medmerry site (apart from during large freshwater discharge events), although greater concentrations of suspended sediment were measured being redistributed internally. Different patterns of sedimentation were observed at two spatially contrasting, but similarly designed, sites. At an exposed nearbreach site, 15.2 cm of accretion were measured over a one year period, whereas rhythmic periods of accretion and erosion were measured at a sheltered location in the centre of the site. Measurements of embryonic creek development suggested that creek formation will occur relatively quickly (< 3 years), but is influenced by the subsurface sediment characteristics. Differences in the subsurface sediment conditions were found to relate to the former land use and changes following site inundation. These findings are discussed relative to the design and construction of MR sites, to improve the success of future schemes in terms of compensating for habitat loss and the provision of coastal flood defence. This is of particular importance as global communities face the implications of future climate change and attempt to sustainably defend against sea level rise, whilst compensating for habitat loss and degradation.
Supervisor: Burgess, Heidi ; Nash, David Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available