IAP2-22-438

Climate change impacts on coastal rockslope erosion

Recent research (Williams et al., 2020; Benjamin et al., 2020) has highlighted the sensitivity of rock slope failure to seemingly small-scale changes in the magnitude and frequency of in rockslope moisture and temperature. Under a changing climate, rockslopes will experience an evolving weather regime that may lead to changes in both the timing and duration of the moisture and temperature conditions which can lead to failure, but our understanding of these changes remains largely anecdotal.

In the UK, sensitivity to such changes is commonly witnessed on coastal rock cliffs, the failure of which leads to the progressive retreat of the coastline. This has been vividly witnessed in recent years, where large winter storms (e.g., Arwen ‘21; Desmond ‘15) resulted in significant localised collapses of coastal cliff faces. Similarly, periods of extreme temperatures during the summer months also appear to drive a greater tendency for rock cliff failure (e.g., https://www.bbc.co.uk/news/uk-england-dorset-62160652). The potential consequence under a changing climate is an increased level of hazard associated with rockfalls from the UK’s coastal cliffs, and as a result, increased rates of coastal retreat.

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Image Captions

Cliffs on the UK north east coast

Methodology

This project seeks to build upon a body of work that has developed high spatial- and temporal-resolution monitoring data to identify the linkages between mass wasting, rock cliff failure and environmental conditions (Kincey et al., 2017; Williams et al., 2018). This project will focus specifically upon these relationships in the context of a changing climate, to consider how coastal rock cliffs may behave in the future. The project will explore a unique 7-year dataset of hourly 3D laser scans and time-lapse thermal imagery that has been used to continuously monitor rockfalls from extensive sections of coastal cliff. The analysis will be used to train a probabilistic model that will explore how climate change may influence erosion and rockfall magnitude and frequency in the future. The project will therefore seek to fill the current knowledge gap around the response of coastal cliffs to climate change, and the implications of new monitoring and modelling data for assessing future risks. The project will be complementary to ongoing research in the long-term COBRA project on the UK’s NE coast led by the project supervisors, and so will benefit from the wider project group and resources (see: https://cobra.webspace.durham.ac.uk/ | https://twitter.com/cobradurham), and the results have the potential to produce valuable public and policy-facing outcomes.

Project Timeline

Year 1

Using archived 3D laser scan and thermal imagery data, the first year of the project will focus upon compiling the 7-year time-series of rockfall from two UK coastal sites. This will involve working with large 3D time series datasets to extract rockfall histories and then to quantify their association with weather conditions at the time of failure. This will build on our previous work on near real-time monitoring of rockslope failure (e.g., Williams et al., 2018). The output of Year 1 will be a publication describing the analysis of this uniquely long-term and high-resolution dataset.

Year 2

Using the empirical relationships identified in Year 1, in Year 2 the project will focus upon building climate change scenarios specific to the conditions favourable to rock slope failure on the UKs coastal cliffs. This will focus upon the exploration of changing timing, duration and magnitude of environmental conditions that lead to rock slope failure.

Year 3

Combining the findings from the analysis of the long-term rockfall archive and the climate change scenarios (Year 2), in Year 3, the project will focus upon developing an ensemble of empirically based models of coastal rock cliff response to a changing climate.  This will specifically focus at two scales: (1) the risks of individual rockfalls; and (2) the net effect of changes in rockfall magnitude and frequency on coastal rock coast retreat.

Year 3.5

In parallel to the write up of the thesis, this period of the project will explore options for innovative outreach and dissemination. Avenues to explore could include the production of public-facing messaging around coastal rockfall risk for use by local authorities, the integration of live monitoring outputs into a ‘coastal rock cliff observatory’, or the use of the data produced by the project for science communication, such as an extension of the Lumiere light festival to sites on the NE coast. Depending on the student, this element of the project may also take a greater role earlier in the research.

Training
& Skills

• Training on 3D terrestrial remote sensing (LiDAR, thermography)
• Large data processing, using Python
• Numerical modelling of climate impact scenarios
• Potential for placements as part of the project outreach and dissemination

References & further reading

Benjamin, J. and Rosser, N.J. and Brain, M.J. (2020) ‘Emergent characteristics of rockfall inventories captured at a regional scale.’, Earth surface processes and landforms., 45 (12). pp. 2773-2787.

Kincey, M.E., Gerrard, C.M. & Warburton, J. (2017). Quantifying erosion of at risk archaeological sites using repeat terrestrial laser scanning. Journal of Archaeological Science: Reports 12: 405-424.

Williams, J. G., Rosser, N. J., Hardy, R. J., Brain, M. J. & Afana, A. A. (2018). Optimising 4-D surface change detection: an approach for capturing rockfall magnitude–frequency. Earth Surface Dynamics 6(1): 101-119.

Williams, J.G., Rosser, N.J., Hardy, R.J. & Brain, M.J. (2020). The Importance of Monitoring Interval for Rockfall Magnitude-Frequency Estimation. Journal of Geophysical Research: Earth Surface 124(12): 2841-2853.

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