How GIS has been used to enable erosion rates to be monitored along this important section of coastline in future years
The internationally renowned coastal exposures of the Jurassic Coast were awarded (inscribed) World Heritage Site status in 2001 based on the near complete sequence of Mesozoic rocks, which record evidence and development of early reptiles through to the age of the dinosaurs.
For a site to obtain World Heritage Site status, it must exhibit cultural or natural features that are ‘of outstanding universal value’ and must be protected for present and future generations of all humanity.
Protecting the integrity (or condition) of the site is essential for maintaining the qualities that led to site inscription. Natural coastal erosion is an important process that maintains the geological integrity and beauty of the Jurassic Coast. Through natural erosion, beaches are replenished with sediment and fossils that have been locked away inside the cliffs are then washed out onto the beach ready for someone to find.
One of the most important locations for Jurassic marine fossils on the coast is area called Monmouth Beach which is near Lyme Regis. Here the towering, crumbling grey cliffs are composed of hundreds of layers of alternating shale and limestone beds dating back to the Jurassic period about 185 million years ago. Within these layers are thousands, if not millions, of marine fossils recording a history of life that is now extinct.
The beach is made up of a series of wave cut platforms of alternating beds of Jurassic limestone and shale. These rocks were laid down at the bottom of a deep sea about 185 million years ago. The ammonite pavement is famous for its dense assemblage of ammonite fossils in a limestone layer that stretches across the wave cut-platforms at Monmouth beach. It is designated as a Site of Special Scientific Interest and is one of the few places along the Jurassic Coast where visitors can openly experience the outstanding universal values of the World Heritage Site.
However the fossil-rich ledges have suffered large scale erosion over the last 5 years. In order to monitor the impact of erosion on this SSSI area, now and for the future, a baseline data survey was needed. Thomas Hearing, a 17 year old pupil at the Thomas Hardye School, Dorchester was awarded a 6 week Nuffield Foundation Science Bursary to work with the Jurassic Coast Team and Bournemouth University to explore this challenge. Thomas was supported in his work by two project mentors; Dr Anjana Ford in the Jurassic Coast Team and Andrew Ford (Lecturer in Geoinformatics) at Bournemouth University.
Over 6 weeks, Thomas used the differential GPS under supervision to map the extent of ammonite-rich ledges and also major crack systems that he could see were contributing to the break-up of the ledge. The main objective of this project was to map the edges of the wave cut platforms on Monmouth Beach in order to provide baseline data that will allow for accurate, quantitative future monitoring of erosion at the Site. Working alongside Andy Ford, a lecturer in Geoinformatics at Bournemouth University, Tom used a series of sophisticated mapping equipment and techniques to map out and examine the geomorphology of the ledges and the nature of their erosion. The investigation focused on the Ammonite Pavement layer, but also recorded the positions of two ledges to the east and six to the south. In addition Tom decided to map the main cracks in the Pavement which may indicate the next areas of major erosion.
The raw data points (about 13,000) gathered at Monmouth Beach had to be interpreted from thousands of numbers into comprehensible information. This meant processing the GPS data and transferring it to a geographical information system (GIS). For the purposes of this project, Tom used the GIS package ArcGIS 9.3 (developed by ESRI UK) at Bournemouth University through the CHEST agreement.
Using the ArcGIS and an orthophotograph sourced from the Channel Coast Observatory, Tom created two maps that showed the current lines of the edges of nine wave cut platforms and the locations of the major cracks in the Ammonite Pavement. The first map showed that a qualitative assessment of erosion could be made from looking at the difference between the polylines and the wave cut platforms on the orthophotograph (since this was taken in September 2006). The data showed that there had been significant erosion of the Ammonite Pavement on the eastern north facing end, where the majority of the large cracks are currently located. It also showed erosion of the two wave cut platforms further up the beach from the Ammonite Pavement, but very little to those on the seaward side. The second map showed significant jointing and cracking on the Ammonite Pavement in an area that has recently experienced significant erosion. If the proposed models of wave cut platform erosion are correct, then larger blocks of limestone will break off in the next decade.
One of the major outcomes of this project has been the creation of a baseline dataset for which to monitor erosion on the Ammonite Pavement, a SSSI and also one of the major fossil sites on the World Heritage Site. This is an important part of meeting conservation policies as set out in the Jurassic Coast Site Management Plan and also strengthens the strategic partnership between The Thomas Hardye School, Bournemouth University and the Jurassic Coast.
The results of Tom’s work were published in the Ordnance Survey publication Mapping News. On March 12th 2010, Thomas beat 200 other finalists at the Big Bang Science Fair to win the prestigious title of UK Young Scientist of the Year. Thomas’s project was the first Earth Science and GIS themed project ever to win the prize and subsequently has opened up the opportunity for GIS to play a role in the delivery of STEM subjects. In addition the Jurassic Coast and Bournemouth University were also awarded the ESRI UK Innovation Award 2010 in GIS for best practice in Communities and Education.
Written by Dr. Anjana Ford, Jurassic Coast Education Coordinator
Jurassic Coast World Heritage Site, County Hall, Dorchester, Dorset, DT1 1XJ
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