2- How did the Porlock pebble ridge alter the morphology of the coast?
As the drift aligned spit gradually enclosed Porlock Bay an area of freshwater and brackish marsh with extensive reed beds began to form behind the pebble ridge fed by three main streams flowing down into the bay from the inland Exmoor plateau. This had the effect of infilling much of the bay and progressively altering it from a saline to a predominantly freshwater or brackish marshland ecosystem. Ballance (2001 p i) says this:
“We do not know very much about the marsh before 1700. In 1420, men were paid for taking cygnets for Lady Harrington from “le lac”, which was presumably then a freshwater pool formed by three main streams behind the shingle bank or “chesil” – see the map of about 1710-1720 (Resource 11). This clearly shows an oval-shaped pool behind the shingle, fed by three converging streams, with a narrow outlet to the sea. It is labelled “Porlock Pill” or Fish Pond. An outlet through the shingle bank is shown and if there was no controllable sluice at this outlet then the pond would have been subject to fluctuations of sea water at high tides”.
Ballance also describes how a large decoy (Resource 13) was constructed on the south west of the marsh sometime during the 18th century. This was a system imported probably from Holland where food attracts wildfowl (mostly wading birds, duck and geese) to a pond from which they are enticed and driven up curved pipes to a catching area. The decoy on Porlock Marsh had ten pipes, an exceptionally large number. Further information about the duck decoy can be found on the Exmoor Historic Environment Record .
Resource 12 shows the building which probably served as the decoy man’s house which fell into disuse by 1820 and was subsequently converted into a linhay – a two storied open fronted building with a hay loft above and livestock housing below. The freshwater marsh ecosystem and particularly a small mere and reed bed fen which developed behind the pebble ridge, comprised a rich and varied mosaic of wetland habitats the importance of which was recognised with the designation of Site of Special Scientific Interest (SSSI) status in 1990. A report from the National Rivers Authority (1992 p 3) described the environment here as ‘a diverse and regionally important site comprising strandline vegetation, shingle, maritime grassland, saltmarsh, swamp and brackish water habitats’.
Consolidate Your Thinking
- What is the purpose of designating locations as SSSIs in England – see http://adlib.everysite.co.uk/resources/000/059/648/NE54.pdf
- For what specific biological reasons was Porlock Marsh designated an SSSI – see the citation at http://www.sssi.naturalengland.org.uk/citation/citation_photo/2000380.pdf
- Make brief notes now on the characteristics of freshwater and brackish wetlands such as that which formed at Porlock Marsh behind the ridge using the links below. Think particularly about their biodiversity and human value:
- Book a Visit
- Exmoor Learning Resources
- Pinkery Centre for Outdoor Learning
- The River Lyn Enquiry
Coastal Management In Porlock Bay
- Introduction and Background
- 1- How have geomorphological processes shaped the coastal landforms at Porlock Bay?
- 2- How did the Porlock pebble ridge alter the morphology of the coast?
- 3- How did human activity alter the marsh?
- 4- Why has the pebble and shingle ridge at Porlock Bay become progressively more vulnerable to breaching?
- 5-Why did the storm of October 28th and 29th 1996 cause a catastrophic breach in Porlock Ridge?
- 6-How has the geomorphic shoreline system at Porlock Marsh changed since October 1996?
- 7-Who actually determines how coastal environments such as Porlock Bay should be managed in the future?
- 8-Why was a policy of limited intervention adopted following the ridge failure?
- 9-Twenty years on what have the costs and benefits of the limited intervention policy been?
- 10-How has the management of change at Porlock Marsh been affected by its location within the protected landscape of Exmoor National Park?
- The Moorland Classroom
- Paddlesteamers, Postcards and Holidays Past
- Exmoor - a Journey Through Time
- Exmoor Facts and Figures
- Did You Know?
- North Hill in World War 2