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Understanding spatio-temporal barrier dynamics through the use of multiple shoreline proxies

Accepted version
Peer-reviewed

Type

Article

Change log

Authors

Pollard, JA 
Brooks, SM 
Christie, EK 
Möller, I 

Abstract

At the coast, risk arises where, and when, static human developments are situated within dynamic surroundings. Barrier islands are often sites of heightened coastal risk since they frequently support substantial human populations and undergo extensive morphological change owing to their low-lying form and persistence in energetic hydrodynamic and meteorological conditions. Using the mixed sand-gravel barrier of Blakeney Point, this study argues that to avoid an only partial understanding of coastal zone processes, it is necessary to make use of multiple shoreline proxies, capturing processes operating both at different timescales and different cross-shore positions. Here, five shoreline proxies were extracted from three data sources. Shoreline error was quantified and compared to observed shoreline change rates to establish proxy-specific, appropriate timescales for shoreline change analysis. The map derived Mean High Water Line at Blakeney Point revealed landward retreat of −0.61 m a−1 over the past 130 years with a shift from drift- towards swash-alignment of the barrier since 1981. Over the past 24 years, the High Water Line, Ridge Line and Vegetation Line reveal proxy-specific response to management regime change. The termination of barrier reprofiling of the eastern section of the barrier has resulted in increased sediment release to the downdrift barrier terminus, buffering retreat there at the expense of the updrift section. The Vegetation Line represents an effective proxy for storm-driven overwash with maximum shoreline retreat during surge events of 172 m, illustrating a strong event-driven component to barrier morphodynamics. By comparison to the other proxies, the LiDAR (Light Detection and Ranging) derived Mean High Water Line offers relatively limited insights into barrier dynamics, emphasising the importance of multi-proxy approaches. In the face of technological advance, we demonstrate the continued importance of critical attention towards the dependencies that exist between shoreline proxy selection and the processes that can be observed as a result.

Description

Keywords

Barrier island, Shoreline proxy, Shoreline change, Shoreline error

Journal Title

Geomorphology

Conference Name

Journal ISSN

0169-555X
1872-695X

Volume Title

Publisher

Elsevier BV
Sponsorship
Natural Environment Research Council (2073548)
Natural Environment Research Council (NE/N015878/1)
NERC (via Cranfield University) (NE/M009009/1)
This work was funded by the NERC/ESRC Data, Risk and Environmental Analytical Methods (DREAM) CDT, Grant/Award Number: NE/M009009/1. It is also a contribution to the NERC-funded project “Physical and Biological dynamic coastal processes and their role in coastal recovery” (BLUE-coast), Grant Award Number: NE/N015924/1.