Emergent characteristics of rockfall inventories captured at a regional scale

Benjamin, J.; Rosser, N.J.; Brain, M.J.

Abstract

High-resolution rockfall inventories captured at a regional scale are scarce. This is partly owing to difficulties in measuring the range of possible rockfall volumes with sufficient accuracy and completeness, and at a scale exceeding the influence of localised controls. This paucity of data restricts our ability to abstract patterns of erosion, identify longterm changes in behaviour and assess how rockfalls respond to changes in rock mass structural and environmental conditions. We have addressed this by developing a workflow that is tailored to monitoring rockfalls and the resulting cliff retreat continuously (in space), in 3D and over large spatial scales (> 10 4 m). We tested our approach by analysing rockfall activity along 20.5 km of coastal cliffs in North Yorkshire (UK), in what we understand to be the first multi-temporal detection of rockfalls at a regional scale. We show that rockfall magnitude-frequency relationships, which often underpin predictive models of erosion, are highly sensitive to the spatial extent of monitoring. Variations in rockfall shape with volume also imply a systemic shift in the underlying mechanisms of detachment with scale, leading us to question the validity of applying a single probabilistic model to the full range of rockfalls observed here. Finally, our data emphasise the importance of cliff retreat as an episodic process. Going forwards, there will a pressing need to understand and model the erosional response of such coastlines to rising global sea levels as well as projected changes to winds, tides, wave climates, precipitation and storm events. The methodologies and data presented here are fundamental to achieving this, marking a step-change in our ability to understand the competing effects of different processes in determining the magnitude and frequency of rockfall activity and ultimately meaning that we are better placed to investigate relationships between process and form/erosion at critical, regional scales.

Citation

Benjamin, J., Rosser, N., & Brain, M. (2020). Emergent characteristics of rockfall inventories captured at a regional scale. Earth Surface Processes and Landforms, 45(12), 2773-2787. https://doi.org/10.1002/esp.4929

• Journal Article Type: Article
• Acceptance Date: Jun 5, 2020
• Online Publication Date: Jul 28, 2020
• Publication Date: 2020-09
• Deposit Date: Jun 5, 2020
• Publicly Available Date: Sep 24, 2020
• Journal: Earth Surface Processes and Landforms
• Print ISSN: 0197-9337
• Electronic ISSN: 1096-9837
• Publisher: British Society for Geomorphology
• Peer Reviewed: Peer Reviewed
• Volume: 45
• Issue: 12
• Pages: 2773-2787
• DOI: https://doi.org/10.1002/esp.4929
• Public URL: https://durham-repository.worktribe.com/output/1300682