Multi-objective optimisation of a rock coast evolution model with cosmogenic ¹⁰Be analysis for the quantification of long-term cliff retreat rates

Shadrick, J. R., Hurst, M. D. , Piggott, M. D., Hebditch, B. G., Seal, A. J., Wilcken, K. M. and Rood, D. H. (2021) Multi-objective optimisation of a rock coast evolution model with cosmogenic ¹⁰Be analysis for the quantification of long-term cliff retreat rates. Earth Surface Dynamics, 9(6), pp. 1505-1529. (doi: 10.5194/esurf-9-1505-2021)

Abstract

This paper presents a methodology that uses site-specific topographic and cosmogenic 10Be data to perform multi-objective model optimisation of a coupled coastal evolution and cosmogenic radionuclide production model. Optimal parameter estimation of the coupled model minimises discrepancies between model simulations and measured data to reveal the most likely history of rock coast development. This new capability allows a time series of cliff retreat rates to be quantified for rock coast sites over millennial timescales. Without such methods, long-term cliff retreat cannot be understood well, as historical records only cover the past ∼150 years. This is the first study that has (1) applied a process-based coastal evolution model to quantify long-term cliff retreat rates for real rock coast sites and (2) coupled cosmogenic radionuclide analysis with a process-based model. The Dakota optimisation software toolkit is used as an interface between the coupled coastal evolution and cosmogenic radionuclide production model and optimisation libraries. This framework enables future applications of datasets associated with a range of rock coast settings to be explored. Process-based coastal evolution models simplify erosional processes and, as a result, often have equifinality properties, for example that similar topography develops via different evolutionary trajectories. Our results show that coupling modelled topography with modelled 10Be concentrations can reduce equifinality in model outputs. Furthermore, our results reveal that multi-objective optimisation is essential in limiting model equifinality caused by parameter correlation to constrain best-fit model results for real-world sites. Results from two UK sites indicate that the rates of cliff retreat over millennial timescales are primarily driven by the rates of relative sea level rise. These findings provide strong motivation for further studies that investigate the effect of past and future relative sea level rise on cliff retreat at other rock coast sites globally.

• Item Type: Articles
• Additional Information: This work was supported by a studentship from the Natural Environment Research Council (NERC) Science and Solutions for a Changing Planet Doctoral Training Partnership (DTP), with additional funding by the British Geological Survey (BGS) to Jennifer R. Shadrick. Dylan H. Rood received support of ANSTO Research Portal (grant no. 10955).
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Hurst, Dr Martin
• Authors: Shadrick, J. R., Hurst, M. D., Piggott, M. D., Hebditch, B. G., Seal, A. J., Wilcken, K. M., and Rood, D. H.
• College/School: College of Science and Engineering > School of Geographical and Earth Sciences
• Journal Name: Earth Surface Dynamics
• Publisher: European Geosciences Union
• ISSN: 2196-6311
• ISSN (Online): 2196-632X
• Copyright Holders: Copyright © 2021 The Authors
• First Published: First published in Earth Surface Dynamics 9(6): 1505-1529
• Publisher Policy: Reproduced under a Creative Commons License
• Data DOI: 10.5281/zenodo.5645478