Monday, 12 May 2014

White Ribbons and Morris Dancing on the Jurassic Coast – by Keith Westhead

In April, a BGS scientific team ventured forth to the spectacular Jurassic Coast in Dorset, famous for the geology, habitats, heritage and tourism which combine to make it a UNESCO World Heritage Site. Here Keith Westhead tells us more about their blustery adventures and shows us some amazing field photos and 3D videos...

Panorama of Stair Hole, with the famous ‘Lulworth Crumple’ on the left (pic: Keith Westhead)

Our task was to use the Dorset coast as a test bed for filling the ‘White Ribbon’, as the often-poorly surveyed and studied ‘gap’ between onshore and offshore geology has become known (and after which our own BGS inshore research vessel is named). This work is part of a strategy across BGS to improve both offshore and coastal geological surveying and modelling and relates to the wider Marine Environmental Mapping Programme (MAREMAP). As a reflection of the multi-disciplinary nature of this work, the team included people from across the BGS scientific programmes - Marine Geology (Keith Westhead), Environmental Modelling (Mark Barron), Engineering Geology (Pete Hobbs and Matt Kirkham) and Climate & Landscape Change (Martin Hurst).

BGS and Channel Coastal Observatory scanning teams
discussing tactics (left to right: Matt Kirkham, BGS,
Andrew Colenutt & Sally Hawkins, CCO) (pic: Keith Westhead)
We met in the field with experts from the Channel Coastal Observatory (CCO) and the World Heritage Jurassic Coast team to discuss integrated research and surveying techniques. We are also working with the University of Southampton on extending the work further offshore. On this fieldtrip, teams from both the BGS and CCO carried out co-ordinated high resolution, ground-based laserscans of the geologically famous Lulworth Cove and Stair Hole localities, and also of the large landslide complexes near Lyme Regis. The two surveys at Lulworth and Stair Hole will be combined to produce a collaborative MAREMAP output. As well as being of interest scientifically, these laser surveys will also be valuable for public communication in an area of great geological interest.


Active landsliding in Lias rocks at Crow’s Nest above Lyme Regis; the BGS and CCO have carried out repeated laserscans of this landscape.

Before we headed into the field, we carried out a phase of ‘virtual fieldwork’ back at BGS, using the host of high-quality digital observational data that already exists in this area – one of the reasons for picking the Jurassic Coast as a White Ribbon test-bed. This includes aerial LiDAR (Light Detection And Ranging), aerial photography and bathymetry (Multibeam Echo Sounder, MBES) data for much of the Dorset coastline and offshore area, collected as part of the Dorset Integrated Seabed Survey (DORIS), a collaboration between the Dorset Wildlife Trust, The Maritime and Coastguard Agency, Channel Coastal Observatory, National Oceanographic Centre and the Royal Navy and others. As the aerial LiDAR surveys were carried out (deliberately) at low-tide, and the bathymetry surveys at high-tide, they actually overlap and enable us to produce a seamless elevation surface across the coastline, perfect for geological and geomorphological studies.

This virtual fieldwork was made possible by using together the BGS-Virtalis GeoVisionary and BGS System for Integrated Geoscience Mapping (BGS▪SIGMAv2012) software packages, which enable us to fly around and map on the elevation surfaces, as well as to analyse them in three-dimensions.

 
Flying along the seamless elevation surface across the coastline from Weymouth to Lulworth Cove, showing the full form of the coastal White Ribbon but ‘bald’ of geology. This surface was produced in GeoVisionary using data from DORIS (DORset Integrated Seabed survey), a collaborative project involving Dorset Wildlife Trust, The Maritime and Coastguard Agency, Channel Coastal Observatory and the Royal Navy, with major funding from Viridor Credits Environmental Company.  Other partners include Natural England, Dorset Strategic Partnership, the National Oceanography Centre and University of Southampton. (vid: GeoVisionary)


Using BGS▪SIGMAmobile and paper maps to study
landslides above Lyme Regis; left to right: Keith Westhead,
BGS, Richard Edmonds, geologist for the  Jurassic Coast
World Heritage Site and Mark Barron, BGS) (pic: Peter Hobbs)
The use of digital surveying techniques doesn’t stay in the lab, as we can now take much of this digital information into the field using the field version of the BGS digital mapping software - BGS▪SIGMAmobile. One of the aims of this field trip was to collect ground-truthing lines using this method, in order to confirm the virtual surveying. We found this integrated lab-and-field surveying approach to be very useful in improving our maps in steep coastal areas, where accuracy is important, for example, for later cliff instability modelling or coastal erosion studies. It can be a strange feeling, however, to actually visit an area after spending a lot of time flying around it digitally back in the office!
 

BGS’s Mark Barron inspecting Blue Lias Formation limestones
exposed at low-tide on the wave-cut platform in Chippel
Bay, west of Lyme Regis.  These limestones form seabed
features which can be traced for kilometres offshore
using bathymetric surveys. (pic: Keith Westhead)


Of course, you can’t spend time surveying at the coast without venturing out onto wave-cut platforms. We were lucky with the tides (and the weather!) and were able to collect information from platforms in the key bedrock marker sequences along the Dorset coast – the Penarth, Corallian, Purbeck Limestone and Portland Limestone groups, for instance. These ‘harder’ groups of rocks form extensive erosional platforms which can be mapped for many kilometres offshore using the detailed bathymetric data. The morphology of these platforms records a long history of relative sea-level fluctuations along the southern coast of the UK, which is one of our developing research threads. In between these limestone and sandstone-dominated bedrock formations, the softer mudstone-dominated sequences, such as, in the Lias Group or Oxford Clay and Kimmeridge Clay formations, form extensive landslide complexes or low-lying bays.  By surveying these variations, we are aiming to produce an accurate, seamless geological map from onshore, through the cliff-sections, across the wave-cut platforms and into the offshore, which gives the true geological picture of the White Ribbon. We hope this will support a much better environmental understanding of the coast, including how both natural processes and human activities may interact with and affect it.

Initial results of the work include this seamless geological bedrock map of the Purbeck coastline from Lulworth to Worbarrow Bay. The mapping is being extended along the whole Jurassic Coast and up to 20km offshsore. (pic: Keith Westhead, GeoVisionary screenshot)

BGS and CCO colleagues standing on a wind-swept Chesil
Beach at West Bay, Weymouth, discussing the effects of
the winter storms on the beach. The crestline of the beach
has been moved back metres in a single year (left to right: Mark
Barron & Martin Hurst, BGS, Stuart McVey and Andrew
Colenutt, CCO). (pic: Keith Westhead)

We were also able to discuss with CCO colleagues the effects on the coastline of the severe winter 2013-14 storms. One of the key aims of the network of Strategic Regional Coastal Monitoring Programmes (for which the CCO are the data management centre) is to identify and monitor natural coastal hazards, such as landslides, rock falls and coastal response to storm conditions to inform flood and coastal erosion risk management, raise awareness of hazards and inform shoreline management and planning to protect life, properties and coastal communities. Understanding how to depict these aspects of applied coastal science in our geological maps and models is an important part of our White Ribbon investigations.

 

Morris Dancers at the Elm Tree in Langton Herring,
part of our evening’s post-work entertainment.
(pic: Keith Westhead)
So, all-in-all, this was a highly useful fieldtrip, with many new scientific ideas generated on how to ‘fill the White Ribbon’, which will support our efforts to improve geological surveying, modelling and research in the complex coastal zone. So look forward to more blogs from the ‘White Ribbon Team’ on our future results!


‘Fill the White Ribbon’ sounds quite like the name of a Morris dance (but isn’t). Coincidentally, after working extremely hard in the evening to write up our work, the team were able to enjoy, and even participate in, a spot of Morris dancing…but we’ll spare you the video of that!

 




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