Will Nature Work With Us? Erosion and Flooding Impacts on a Uk Barrier

Abstract

Barrier island' refers to a diverse collection of coastal landforms that often support substantial human populations, critical infrastructures, and ecosystems. Globally, many coastal barriers are experiencing climatically altered environmental forcing coupled with increasing anthropogenic pressures. This paper undertakes high resolution shoreline change analysis to reveal how Blakeney Point, a mixed sandy-gravel barrier located on the UK's East Coast, has evolved over centennial, decadal and event timescales. We seek to establish the implications of barrier evolution, under contrasting management regimes, for present erosion and flooding hazards. Interrogating a series of alternative shoreline proxies reveals a series of interdependent behaviors. Over the 130-year period of study, Blakeney Point is shown to be rolling landward at a mean rate of 0.60 m a-1. Assuming continued landward retreat over the coming decades, future flood-generating storm events will encounter more landward shoreline positions than today. Superimposed on this trend, we observe the presence of alongshore migrating erosional hotspots which give rise to unpredictable morphologies at any given location on the spit. Finally, we find that instances of barrier setback are driven by individual storm events, which makes barrier retreat both highly variable and discontinuous in time and space. This is illustrated by the presence of overwash, particularly along stretches of the barrier that have experienced a recent shift in management regime towards a non-interventionist approach.

Long-Term Trends, Short-Term Shocks and Cliff Responses for Areas of Critical Coastal Infrastructure

“…The clifftop edge can be clearly defined on both data types. The maps and photographs were georectified to be within the same coordinate system (OSGB36) and then digitized to generate shorelines for individual years (see Pollard et al 2019 for a discussion of errors associated with digitisation). The ArcGIS add-on, the Digital Shoreline Analysis System (DSAS; Thieler et al 2009), was then used to quantify long-term cliff retreat rates, with an alongshore shore-normal transect spacing of 5 m, over the 12 km cliff frontage between Mundesley and Walcott.…”

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

“…Summary of total shoreline change and shoreline change rates for five shoreline proxies from three data sources. Revised fromPollard et al, 2019b. Mean RMST error bands were applied to each shoreline proxy and are shown in brackets.…”