Real time laser mapping for monitoring coastal erosion and rockfall

3D Laser Mapping, a global laser scanning technology provider and Durham University have created an innovative monitoring system to provide real time 3D data on coastal cliff erosion. The project is part of a KTP (Knowledge Transfer Partnership), a scheme funded by Innovate UK, which has a track record of improving businesses’ competitiveness, productivity and performance by accessing the knowledge and expertise available within UK Universities and Colleges.

Understanding the nature and mechanisms of cliff erosion is of vital importance to predicting the likely future movement of the coastline. Research on eroding coastlines has been limited by the need for surveys of coastal areas, which are restricted to periods of low tides each month.

The project aims to try to understand the processes of coastal erosion by looking at projected increases in sea level and stormy weather. It aims to understand the process through which wave erosion at the base of the cliffs causes undercutting of the cliff slope which results in an unstable cliff and failure of material that falls into the sea. Whilst this process may at first glance appear straightforward, research by Durham University over the last decade has shown current understanding to be largely anecdotal. The linkage between waves and erosion evolves gradually through time, and is one that responds to a wide range of factors, and not just the action of waves alone.

Diagram of the full instrumentation used to make up the system

The project seeks to take advantage of uniquely high-resolution, 3D data being continually captured, to generate unprecedented detail on the changes experienced at cliffs. The 3D Laser Mapping Site Monitor system automatically schedules the capture and analysis of 3D laser scan data in parallel with environmental monitoring data. The seaside town of Whitby now has one of – if not the most – intensively monitored rock faces in the world.

The project provides constant and frequent measurement of the cliff face, to allow changes resulting from rockfall to be recorded and analysed in real time. The system is designed to scan the cliff face 24 hours a day at 30 minute intervals. Within each scan measurements of the cliff face are taken at approximately 10 cm intervals, generating over 2 million points per scan. Whilst this data capture is itself uniquely innovative, the analysis of such a large volume of information presents significant challenges. To overcome this, the system streams data live from Whitby to Durham, where new algorithms have been developed to process the 3D data to extract rockfall volumes in real time.

Whitby webcam, 31 March 2015

 

An example of the data that is captured by the system every 30 minutes is shown above. This image shows a 3D view of the cliff, captured in February 2015. On the right it is possible to see the cottages at the end of Henrietta St, the walkway down to the pier, and East Cliff. This image is taken from measurements every c. 10 cm across the cliff face. The webcam shot is an image of the same area of the cliff, taken from the viewpoint of the monitoring system.

Using these results, the project is designed to tackle the challenge of precisely monitoring coastal cliff erosion and gain a new understanding from this. For example, it is known that many landslides and rockfall are preceded by precursors, such as smaller-scale movements or smaller rockfall, yet capturing data with sufficient resolution and frequency has up until now not been possible. The intention of this analysis is to investigate these processes with a view to both better forecasting erosion, and also assessing whether such precursors can be used as warnings for future rockfall.

The intention of the research is to move beyond Whitby and the UK’s coasts. The more usual location of 3D Laser Mapping’s Site Monitor system is in some of the world’s largest open pit mines, where rockfall and slope failure presents a significant challenge for sustaining mine productivity. The insight into the fundamental mechanics of how rockfall evolves, gained from the research at the cliffs in Whitby, is designed to be transferrable to these settings and enhance the reliability of slope failure early warning systems.

The help of the local community has been key in enabling the infrastructure for this project. The findings will be available through an open access website soon so everyone involved will be able to see the results as they happen.

Monitoring 3D laser mapping

3D Laser Mapping are supported by the Royal Academy of Engineering under the Pathways to Growth scheme. For more information on the scheme please contact Catherine Lawrence E-mail: Catherine.lawrence@raeng.org.uk). For more information on the activities detailed in the article please contact Eileen Pegg (01949 838004; E-mail:eileenpegg@3dlasermapping.com) and /or visit www.3dlasermapping.com and www.dogweb.dur.ac.uk/cobra.

 

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