Marine control over negative power law scaling of mass wasting events in chalk sea cliffs with implications for future recession under the UKCP09 medium emission scenario

Abstract

Coastal cliff erosion represents a significant geohazard for people and infrastructure. Forecasting future erosion rates is therefore of critical importance to ensuring the resiliency of coastal communities. We use high precision monitoring of chalk cliffs at Telscombe, UK to generate monthly mass movement inventories between August 2016 and July 2017. Frequency-magnitude analysis of our inventories demonstrate negative power law scaling over 7 orders of magnitude and, for the first time, we report statistically significant correlations between significant wave height (H s ) and power law scaling coefficients (r 2 values of 0.497 and 0.590 for β and s respectively). Applying these relationships allows for a quantitative method to predict erosion at the site based on H s probabilities and sea level forecasts derived from the UKCP09 medium emission climate model (A1B). Monte-Carlo simulations indicate a range of possible erosion scenarios over 70 years and we assess the impact these may have on the A259 coastal road which runs proximal to the cliffs. Results indicate a small acceleration in erosion compared with those based on current conditions with the most likely scenario at the site being 21.7 m of cliff recession by 2090. However, low-probability events can result in recession an order of magnitude higher in some scenarios. In the absence of negative feedbacks, we estimate an~11% chance that the A259 will be breached by coastal erosion by 2090.

Marine and subaerial controls of coastal chalk cliff erosion in Normandy (France) based on a 7-year laser scanner monitoring

“…One of the challenges in the research is to foresee coastal evolution to ensure the resiliency of coastal communities (e.g. Gilham et al, 2018).…”

Detection and analysis of mass wasting events in chalk sea cliffs using UAV photogrammetry

“…This research uses frequency densities, which provide an estimate of the production rate of each rockfall volume class, whilst the cumulative method provides a probabilistic hazard estimate of exceeding a given volumetric threshold. The method used for this research has previously been applied to the study of sea cliffs by Barlow et al (2012) and Gilham et al (2018).…”

“…This is evidenced by the wedge failures at the site (Mortimore et al, 2004;Barlow et al, 2017) which constrain the magnitude of the observed larger failures in the inventory presented. Using these data, Gilham et al (2018) found that the power law scaling parameters (β and s) are correlated to Hs at Telscombe and developed a probabilistic recession model based on the UK Climate Change Projection (UKCP) 2009 medium emission scenario.…”

Decoding Complex Erosion Responses for the Mitigation of Coastal Rockfall Hazards Using Repeat Terrestrial LiDAR

“…Rockfall, or the removal of individual and superficial rocks from a cliff face [1,2], is a significant geohazard, particularly on coastal cliffs where the exposure of people and assets is often high [3,4]. Rock coasts account for much of the world's coastline [5], yet our understanding of their evolution remains limited by progressive time-dependent failure processes [6], geological and geometric settings [7][8][9], increasing environmental extremes [10,11], and the appropriateness of the available…”