Climate Change & Coastal Heritage

Welsh Project Areas

13 March 2021• Welsh Project Areas

13. Castlemartin to Stackpole Warren

News Letter

Location Map

Introduction

The coastline between Castlemartin to Stackpole Warren area is well known for its impressive high limestone cliffs upon which many prehistoric promontory forts were built. Many of these sites have suffered in the past from coastal erosion, with some sites now almost entirely lost to the sea. The sand dunes at Stackpole Warren are also extremely interesting and contain valuable information relating to how weather patterns have changed in the past and how they shaped the coastal landscape we see today. The sand dunes have also covered and preserved important Bronze and Iron Age archaeological sites.

Aerial photograph of the Castlemartin coastline.
Aerial photograph of the Castlemartin coastline.

Castlemartin Promontory Forts

This part of Pembrokeshire is blessed with an abundance of promontory forts which range from single ditch enclosures to monumental structures. Many of these sites have benefitted from being located within the boundaries of the Castlemartin practice firing area where they are now effectively ‘defended’ by the army. However, whilst they are well protected from human interference, they are not so protected from the forces of nature which have had noticeable impacts upon the archaeology.
Flimston Bay Promontory fort with its distinctive eroded ‘cauldron’.
Flimston Bay Promontory fort with its distinctive eroded ‘cauldron’.

Within this area CHERISH are monitoring and researching five promontory forts: Linney Head, Flimston Bay, Crocksydam, Crickmail Down, and Buckspool Down. Each is unique in the nature of the landscape it occupies and the ways in which they were constructed. Through using a combination of UAV and analytical earthwork surveys CHERISH is not only monitoring recent erosion but also researching some of the many outstanding archaeological questions previously not addressed.

There is also the site of Castlemartin Corse which is a valley wetland that has been strongly influenced by coastal weather systems and a large, mobile dune complex which is gradually moving inland. CHERISH has cored the wetland and recovered a core of sediment that dates back about 5000 years. Through using this technique, it is hoped that patterns of storm frequency and intensity in the bio and geochemical record can be identified to increase the understanding of present and future climatic change.
Linney Head Promontory fort.
Linney Head Promontory fort.

Stackpole Warren

In the east of the project area is the extensive system of sand dunes known as Stackpole Warren. Unusually, the dunes here are situated on top of high limestone cliffs which rise to around 20m above sea-level. The Warren is rich in archaeological evidence of occupation from the Mesolithic to the Roman Period. Excavations have indicated that the sand was mobilised in at least two distinct phases, the first in the Late Bronze age and then intermittent sand movement during the Iron Age to Romano British Period.

CHERISH has recovered cores from three areas on Stackpole Warren, which will be dated using Optical Stimulated Luminescence (OSL) to improve our understanding of when these sand movement events took place. It may also be possible to determine over what sort of timescales sand deposition took place. Through this work CHERISH hopes to stimulate a wider appreciation of the lives of the early inhabitants in this area, and the climatic challenges they encountered.

The sand dunes at Castlemaritn Corse.
The sand dunes at Castlemaritn Corse.

Why are we working here?

Coastal erosion has had a noticeable impact upon the archaeology in this region where large proportions of sites haven fallen into the sea. CHERISH is working in this area to provide baseline data for sites that have seen little attention from archaeologists in the past. Archaeological and paleoenvironmental research will also draw wider conclusions about regional patterns of climatic variability in the past as well as identify the main processes causing the erosion.

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12 March 2021• Welsh Project Areas

12. Grassholm Island, Skomer Island & The Marloes Peninsula

News Letter

Location Map

Introduction

Grassholm Island, Skomer Island and the Marloes Peninsula form an important part of the unique prehistoric and historic coastal landscape of south Pembrokeshire. The coastline of the Marloes Peninsula is also renowned for shipwrecks of vessels travelling between Ireland, south Wales and the south of England.

Grassholm Island and Skomer Island

Aerial oblique photograph of Midland Isle, Skomer Island.
Aerial oblique photograph of Midland Isle, Skomer Island.

Grassholm and Skomer Island are two archaeologically rich islands situated off the west coast of the Marloes peninsula in south Pembrokeshire. Amongst the thousands of gannet nests and puffin burrows that cover the islands are the remains of countless mysterious stone structures, inter-linking stone field boundaries, ploughed lynchets and other archaeological features. The visible remains represent human occupation and farming on the islands that span both the prehistoric and medieval periods. Recent research by CHERISH has illuminated some of the islands’ mystery through exploring and recording its eroding archaeology.

Archaeological research has been ongoing on Skomer since 2011 and has been undertaken by archaeologists from the Royal Commission, The University of Sheffield and Cardiff University as part of the Skomer Project. A major product of the project was the collection of 0.50cm LiDAR data for the entire island from which archaeological mapping was carried out. This work resulted in the mapping of countless Bronze Age, Iron Age and medieval field systems, many of which were previously not known about. This work essentially laid down the building blocks for the CHERISH LiDAR data collection of a further six islands (including Grassholm) in 2017.

Aerial photograph of Grassholm Island.
Aerial photograph of Grassholm Island.

The LiDAR survey of Grassholm allowed for the precise identification and mapping of all surviving prehistoric structures and field boundaries spread across the island. Based on this work several areas of interest were identified which were investigated during a 2019 visit by CHERISH. The main priority for the team was to undertake a rapid two-day evaluation excavation of a single stone-built structure towards the centre of the island that had become exposed due to the erosion of the previously overlying vegetation. A small segment of one of the structure’s walls was excavated to characterise the way in which it was constructed and to recover any possible artefactual evidence. The small part of the structure that was uncovered was very well-built, however, a lack of dating evidence made dating the structure extremely difficult.

Digital Elevation Model (DEM) of Grassholm Island generate from LiDAR data.
Digital Elevation Model (DEM) of Grassholm Island generate from LiDAR data.

Marloes Peninsula

The Marloes peninsula is home to beautiful beaches, impressive cliffs and dangerous waterways. The impressive coastline is peppered with a fine selection of prehistoric promontory forts and coastal settlements which take full advantage of the natural topography as well as several shipwrecks which serve as a reminder of the treachery of seafaring. CHERISH is researching one particular wreck named ‘The Albion’ which is located at Albion Sands to the south west of Marloes. The wooden paddle steamer was built at Bristol in 1831 by General S P Company to transport people and goods between Bristol from Dublin. In 1837 the ship’s captain was forced to change course to avoid running down a rowing boat with four men on board. The change of direction and the force of the tide caused the Albion to strike a rock which forced the ship to run aground at Marloes. The wreck is now being monitored by CHERISH to analyse how storm events influence sand movement in the exposure and inundation of the wreck.
Different components of the Albion shipwreck site including storm scour (1), remains of the boiler (2), crankshaft (3) piston rod (4), and crankshaft bearing frame.
Different components of the Albion shipwreck site including storm scour (1), remains of the boiler (2), crankshaft (3) piston rod (4), and crankshaft bearing frame.

Why are we working here?

Although this area is archaeologically significant little is known about the coastal and island sites. Archaeological research undertaken by CHERISH is beginning to address some of these knowledge gaps and uncover some of the archaeological stories of this historically important coastline. Important data collected by the project (such as LiDAR, UAV and GNSS data) also provides an important baseline dataset that can be used in the future to monitor possible changes at the coast edge.

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11 March 2021• Welsh Project Areas

11. Porth y Rhaw

News Letter

Location Map

Introduction

Porth y Rhaw (translation: port of the shovel or oar) is one of the most impressive yet heavily eroded promontory forts in Pembrokeshire. The fort occupies a relatively inconspicuous position on an extremely craggy and eroded stretch of coastline approximately 1.1km to the west of Solva. Hidden amongst countless other small promontories, crags and coves the site takes advantage of a steep sided natural promontory which has been sculped to produce a series of landward-facing ramparts and ditches. Archaeological surveys and excavations have revealed that Porth y Rhaw was constructed and settled during the early Iron Age – Romano British period (800BC – 400 AD) however evidence suggest that the site was not occupied for the whole of that time. The defences were also remodelled at least five times likely reflecting various changes in the site’s function over the course of its long history.
Aerial photograph of Porth y Rhaw. Visible are the series of banks and ditches that enclose the central eroded chasm and the eastern promontory.
Aerial photograph of Porth y Rhaw. Visible are the series of banks and ditches that enclose the central eroded chasm and the eastern promontory.

Why are we working here?

Coastal erosion has had a very noticeable impact upon Porth y Rhaw which has shaped the site over thousands of years. CHERISH is working at the site both to provide objective 3D data for erosion monitoring and to further understand the threated archaeology of the site. Detailed archaeological research has highlighted that visible erosion is by no means a modern phenomenon, with the builders respecting the huge eroded central chasm by building the defences around it. Previous interpretations suggested that the chasm had largely formed after the site was constructed. 

Excavation of the inner entranceway at Porth y Rhaw undertaken by Dyfed Archaeological Trust in 2019.
Excavation of the inner entranceway at Porth y Rhaw undertaken by Dyfed Archaeological Trust in 2019.

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10 March 2021• Welsh Project Areas

10. Ramsey Island & Caerfai Camp

News Letter

Location Map

Introduction

Ramsey Island and Caerfai Camp form part of the important prehistoric coastal landscape of St David’s peninsula which boasts at least twelve coastal promontory forts including the impressive Clawdd y Milwyr on St David’s Head.

Ramsey Island

Ramsey Island is separated from the mainland by the treacherous Ramsey Sound to the west of St Davids. The history of human interaction with the Ramsey can be traced back to the Bronze Age period over 4,000-5,000 years ago through the presence of round barrows, cairns and field boundaries across the island. It was also an important place during the medieval period where it was known in legend as being burial place of 20,000 saints. The two chapels of St Justinians and St Tyfanog’s are also recorded to have been located on the island during the medieval period.
CHERISH has used Airborne Laser Scanning (ALS) and Historical aerial photography to identify and map all visible archaeological monuments on the island in order to improve and expand upon the existing monument records for the island.
Digital elevation model (DEM) of Ramsey Island created from the ALS data.
Digital elevation model (DEM) of Ramsey Island created from the ALS data.

Caerfai Camp

The promontory fort site of Caerfai Camp (possible translation: blamed walled city) occupies a very large and visually dominant natural coastal promontory approximately 1.3km to the southeast of the city of St David’s. This site is unique in the way that is occupies the tip a long natural promontory that protrudes around 500m into St Bride’s Bay where it would have been extremely visible to past seafarers. The site is made distinctive by its heavily eroded ‘chasm’ which over time has eroded to create a sub-rectangular parcel of land connected at the very tip of the long natural promontory. Running parallel to the chasm on its northern side is a series of four banks and ditches which were constructed and adapted throughout the prehistoric period. Interesting is the way that the constructed defences appear to respect where the erosion has occurred.
Aerial image of Caerfai Camp taken using UAV.
Aerial image of Caerfai Camp taken using UAV.

Why are we working here?

Coastal erosion has had a noticeable impact upon the archaeology in this region, especially at Caerfai where there a considerable amount of the site has been lost to the sea. Archaeological and paleoenvironmental research of this area will also draw wider conclusions about regional patterns of climatic variability in the past as well as identify the main processes causing the erosion

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The village of Cwm-yr-Eglwys which has been subject to severe storms throughout history.

10 March 2021• Welsh Project Areas

9. Dinas Island & Cwm yr Eglwys

News Letter

Location Map

Introduction

Few sites illustrate coastal erosion, loss and environmental change more than the headland of Dinas Island and the village of Cwm yr Eglwys. The headland has been delineated from the mainland through glacial processes creating a narrow u-shaped valley, some 70 metres deep. The cluster of cottages at the northern end of the valley makes up the hamlet of Cwm yr Eglwys.

Most notable landmark in valley is the ruined church dedicated to St. Brynach which sites on a platform some 3 metres above and immediately behind the beach. It is surrounded by a handful of weathered headstones. 


The church was damaged by storm of 1850 and 1851 destroying the chancel and removing the surface of the cemetery exposing human remains. The final straw came in the Royal Charter Storm of 1859 which demolished the walls and roof leading to its abandonment. Erosion has been stabilised for now by the construction of modern concrete sea walls, but it uncertain how future climate change and sea-level rise might impact the cove.

Visible are the remains of the church heavily damaged by a series of intense storms during the 1850s. The more modern sea defences represent an ongoing struggle between the village of the sea.
Visible are the remains of the church heavily damaged by a series of intense storms during the 1850s. The more modern sea defences represent an ongoing struggle between the village of the sea.

Why are we working here?

A swampy carr-fen occupies the central portion of the valley floor. The fen is an important archive of past environmental change, which has previously been shown to extend back to the last glaciation. CHERISH is hoping to re-examine these deposits using the latest high resolution x-ray fluorescence techniques to look for chemical signals that might be used to reconstruct storm patterns and evidence of past environmental change.

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