A Method to Extract Measurable Indicators of Coastal Cliff Erosion from Topographical Cliff and Beach Profiles: Application to North Norfolk and Suffolk, East England, UK

Abstract

Recession of coastal cliffs (bluffs) is a significant problem globally, as around 80% of Earth’s coastlines are classified as sea cliffs. It has long been recognised that beaches control wave energy dissipation on the foreshore and, as a result, can provide protection from shoreline and cliff erosion. However, there have been few studies that have quantified the relationship between beach levels and cliff recession rates. One of the few quantitative studies has shown that there is a measurable relationship between the beach thickness (or beach wedge area (BWA) as a proxy for beach thickness) and the annual cliff top recession rate along the undefended coast of North Norfolk and Suffolk in eastern England, United Kingdom (UK). Additionally, previous studies also found that for profiles with low BWA, the annual cliff top recession rate frequency distribution follows a bimodal distribution. This observation suggests that as BWA increases, not only does cliff top recession rate become lower, but also more predictable, which has important implications for coastal stakeholders particularly for planning purposes at decadal and longer time scales. In this study, we have addressed some of the limitations of the previous analysis to make it more transferable to other study sites and applicable to longer time scales. In particular, we have automatised the extraction of cliff tops, toe locations, and BWA from elevation profiles. Most importantly, we have verified the basic assumption of space-for-time substitution in three different ways: (1) Extending the number or years analysed in a previous study from 11 to 24 years, (2) extending the number of locations at which cliff top recession rate and BWA are calculated, and (3) exploring the assumption of surface material remaining unchanged over time by using innovative 3D subsurface modelling. The present study contributes to our understanding of a poorly known aspect of cliff–beach interaction and outlines a quantitative approach that allows for simple analysis of widely available topographical elevation profiles, enabling the extraction of measurable indicators of coastal erosion.

A combined approach to cliff characterization: Cliff Stability index

“…1), such as the Twelve Apostles (Australia), the Minamijima Island (Japan), the Pigeon Rocks (Lebanon), the Catedral (Peru), the Darwin Arch (Ecuador), the Portada (Chile), the Arco de Cabo San Lucas (Mexico), the Holei Sea Arch and Sunsent Cliffs (United States), the Perce Rock (Canada), the Hvitserkur (Iceland), the Cliffs of Moher (Republic of Ireland), the Arch Rock in Arnarstap (Ireland), the Stacks of Duncansby, Yesnaby and Thirle Door (Scotland), the Green Bridge (Wales), the Durdle Door, Flamborough Head and Old Harry Rocks (England), the Azure Window (Malta), the Drangarnir (Faroe Islands), the Porte d'Aval (France), the Quebrada coast, Cuevas del Mar beach and Cathedral beach (Spain), or the Ponte da Piedade (Portugal), among others. Numerous works have studied erosion problems on cliff coasts over the last decades (Sunamura, 1977;Robinson, 1977;Jones and Williams, 1991;Komar and Shih, 1993;Shih and Komar, 1994;Duperret et al, 2002;Moore and Griggs, 2002;Sallenger Jr et al, 2002;Rosser et al, 2005;Hansom et al, 2008;Dawson et al, 2009;Hapke and Plant, 2010;Lim et al, 2011;De Rose and Basher, 2011; Barlow et al, 2012;Dickson et al, 2013;Carpenter et al, 2014;Jones et al, 2015;Johnstone et al, 2016;del Río et al, 2016;Pappalardo et al, 2017;Earlie et al, 2018;Prémaillon et al, 2018;Westoby et al, 2018;Terefenko et al, 2018Terefenko et al, , 2019Zelaya Wziatek et al, 2019;Alessio and Keller, 2020;Muñoz-López et al, 2020;Di Crescenzo et al, 2021). For example, Sunamura (1977) proposed, based on field and laboratory data, a rel...…”

Sediment Thickness Model of Andalusia’s Nearshore and Coastal Inland Topography

“…Coastal decision-makers now have an evidence-based model of the coastal zone that can be used to better manage the risk of coastal flooding and erosion. As shown by [43], a better quantification of the amount of unconsolidated material along the coast enables a better quantification of the level of protection offered against coastal erosion and interlinked coastal flooding. This allows the coastal stakeholder to define trigger points for interventions to ensure the minimum level of protection is secured.…”

Innovative Representation of the Coastal Topo-Bathymetry and Subsurface for Flooding and Erosion Risk Reduction

“…This Special Issue titled "Innovative Representation of the Coastal Topo-Bathymetry and Subsurface for Flooding and Erosion Risk Reduction" includes eight contributions [1][2][3][4][5][6][7] published during 2020-2022. Overall, the aim of this Special Issue is to collect studies that that have: (i) developed better ways of representing (i.e., 3D subsurface models) [2] and monitoring (i.e., satellite-derived bathymetries, subsidence, etc.)…”

“…Overall, the aim of this Special Issue is to collect studies that that have: (i) developed better ways of representing (i.e., 3D subsurface models) [2] and monitoring (i.e., satellite-derived bathymetries, subsidence, etc.) [1,3] the coastal zone structure; (ii) translated current geological understanding into more ready-to-use information for coastal engineering consultants and stakeholders (i.e., shoreline rate of change, sediment yields from an eroding coast and coastal vulnerability assessments) [4,6]; and (iii) contributed to our understanding of the 4D evolution of the coastal zone structure [7]. The scientific collection presented herein will be of importance to scientists, engineers, and coastal stakeholders with an interest in evidence-based decision making to better manage the risk of coastal flooding and erosion.…”

“…Muñoz-López et al (2020) [7] proposed and demonstrated a new method to measure the relationship between beach levels and cliff recession rates. This is one of the few quantitative studies to show a measurable relationship between the beach thickness (or beach wedge area (BWA) as a proxy for beach thickness) and the annual cliff top recession rate along the undefended coast of North Norfolk and Suffolk in eastern England, UK.…”