The Loe

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The Loe

The Loe or Loe Pool is the largest natural freshwater lake in Cornwall, a pool close by the sea but permanently cut off from it by a broad shingle bar, the Loe Bar, built up by heavy Atlantic seas.

The Loe is in a gap in the cliffs between Porthleven and Gunwalloe, and downstream of Helston. It extends over 124 acres and has a maximum depth of 20 feet.

The surrounding Penrose Estate is a mixture of rich farmland and woodland around Loe Pool, through which there are many paths to explore

Geography

Both the Loe (including the southern arm known as Carminowe Creek) and Loe Bar are within the Penrose Estate, administered by the National Trust,[1] and are designated as a Site of Special Scientific Interest by Natural England.[2] It is also designated as an Area of Outstanding Beauty AONB[3] and is considered a classic Geological Conservation Review Site.[4]

Origins

The Loe was once thought to have been a rivermouth which was blocked in historic times, but it is now generally accepted that it is more ancient than that. It is in form the estuary of the River Cober, and a "ria" or drowned river valley now blocked by a sand and shingle bar to leave the fresh water lake behind. The valley can be traced several miles out to sea.

The age of the bar is disputed, with estimates ranging from several thousand years to c. 700 years. The most likely origin is a barrier beach, that gradually moved onshore, as the sea level rose during the Holocene. The shingle coming from drowned terraces of the former river that flowed down the English Channel.[4] It is thought that Longshore Drift plays an important part in the maintenance of the Bar, with a strong current flowing to the south-east from Porthleven to Gunwalloe, depositing shingle along the Bar. The ebb flow is not a simple reverse flow and is not strong enough to remove all the deposits.[5] The bar itself is a sediment sink as far as the overall beach budget is concerned.[4] The deposits have been tentatively dated as Eocene, and compared with Gunwalloe beach material very little of the Loe Bar shingle is locally derived. The composition of the Bar deposits are: Chalk flint 86%, Quartz 9%, Grit 2.6%, Greensand chert 2% and Serpentine 0.5%.[5] The nearest onshore source is 120 miles away in East Devon.[6]

To prevent flooding in parts of Helston, the Bar has occasionally been breached, a practice known locally as "cutting[7]". However, it has always naturally resealed itself.[6]

History

  • C13th. The townspeople of Helston buy the rights to the port of Gweek at the head of the Helford River as Helston did not have access to the sea.[6]
  • 1272 King Edward I granted certain lands in or near Helston to William de Treville on condition that he should, at his own expense, bring a boat and fishing-hook and net for the King's use on the Loe, as often as he should visit the Borough.[8]
  • 1281 The first documentation of the name Penrose; John de Penrose.[6]
  • 1534-43 Visits by John Leland was the first to mention the "casting up of sands that made a bar stopping the River Cober from flowing out to Sea."' [9]
  • 1602 Richard Carew. "The shingle was relatively porous and fresh water could leave and seawater enter depending, on the relative heights of the pool and sea".[10]
  • 1771 Penrose bought by the Rogers family for £11 000.[6]
  • 1780 Adit constructed to prevent back-flooding of the silver and lead mine Castle Wary, also known as Wheal Pool.[5]
  • 1807 Over one hundred people were drowned when the 44-gun frigate Anson, beached the on the Bar in storm sailing to the Brest blockade. A consequence of this disaster was the development of the rocket life-saving apparatus by Henry Trengrouse who witnessed the wreck.[6]
  • 1837 Report on the possibility of creating a harbour by the civil-engineer James Rendle. The estimated cost of £118,523 was considered too expensive to take the project further.[11][6]
  • c. 1850 Tin waste from the mines at Porkellis Moor begin to block the inner face of the Bar reducing the porousness.[12]
  • 1865 Breach of the Bar.[13]
  • 1874 The last known manual cutting of the bar.[5]
  • 1889 Enlargement of the 1780 adit which regulated outflow.[5]
  • 1924 Freak wave caused flooding in Helston.[5]
  • 1938 Mining activity ceased up river.[5]
  • c. 1940 Loe Bar mined and timber baulks or booms moored on the surface of the Loe to prevent seaplanes landing. A pillbox was built near Bar Lodge.[6] By 2010 erosion had caused the pillbox to fall onto the beach.
  • 1974 Ownership of the Penrose Estate (apart from the house) is transferred to the National Trust.[6]
  • 1979 First cutting of the bar by JCB.[14]
  • 1984 Heavy rains in October and November require another cutting - the last of the 20th century.[5]

Wildlife and habitats

Loe Bar

The beach from Porthleven to Gunwalloe is important for coastal geomorphology as it is formed by a barrier beach moving onshore since the Holecene and maintained by a predominantly south-west wave regime. During storms the Bar can be overrun by the sea forming a series of washover fans resulting in, annual laminated sediments, which are unique in Great Britain.

The habitat is unique in Cornwall with rare species of plants, bryophytes, algae and insects. It is also an important overwintering site for nearly 80 species of birds and up to 1200 wildfowl. At the assessment on 8 September, 2010 the lake was found to be unfavourable condition, with no change from the previous assessment. The reasons being inappropriate water levels, and water pollution due to agriculture run off and discharge from the sewage treatment works upstream below Helston.[15]

Loe Bar is the only site in Great Britain where the subspecies leechi of the Sandhill Rustic moth is found.[16]

Porcellio dilatatus is an uncommon species of woodlouse with scattered records from most of the British Isles. Loe Pool is the only Cornish site. Also found on each of the inhabited islands of the Isles of Scilly.[17]

Folklore

The Loe is reputed to be the lake in which Sir Bedivere cast King Arthur's sword, Excalibur.[6]

A local legend states that the giant Tregeagle was doomed to remove the sand from Gunwalloe to Porthleven, from which the sea would return it. In the course of one of his journeys he is said to have dropped a bag of sand at the entrance of Helston harbour and so to have formed the Bar.[8][6] Local superstition also warns that the Loe claims a victim every seven years.[6]

Outside links

References

  1. ↑ National Trust. Penrose Estate: Gunwalloe and Loe Pool. Accessed 28 November 2010.
  2. ↑ Natural England. SSSI units for Loe Pool. Accessed 28 November 2010.
  3. ↑ Cornwall Area of Outstanding Natural Beauty. http://www.cornwall-aonb.gov.uk/
  4. ↑ 4.0 4.1 4.2 May, V.J. Loe Bar. In May, V.J. and Hansom, J.D. (2003) Coastal Geomorphology of Great Britain, Geological Conservation Review Series, No. 28, Joint Nature Conservation Committee, Peterborough, 754 pp.
  5. ↑ 5.0 5.1 5.2 5.3 5.4 5.5 5.6 5.7 Murphy, R.J., (1986). A Study of Loe Bar. In Cornish Studies 14:23-33.
  6. ↑ 6.00 6.01 6.02 6.03 6.04 6.05 6.06 6.07 6.08 6.09 6.10 6.11 Le. Messurier, B. and Luck, L. (1998) Loe Pool and Mount's Bay. No. 12 in The National Trust Coast of Cornwall series of leaflets.
  7. ↑ Davies, David. "Loe Bar: A Geomorphological Analysis". http://freepages.history.rootsweb.ancestry.com/~helstonhistory/loebarpage.htm. Retrieved 26 March 2012. 
  8. ↑ 8.0 8.1 Toy, H. S. (1936) The History of Helston. Oxford University Press
  9. ↑ Chope, R. P. (Ed.) (1918). Early Tours in Devon and Cornwall. Itinerary of John Leland (1534-43), pp. 30-1, cited in Murphy, R. J. (1986). A Study of Loe Bar. In Cornish Studies 14:23-33.
  10. ↑ Martin, B. (c. 1770). The Natural History of Cornwall and Devonshire.
  11. ↑ Rendle, J. M. (1837). Report on the practicability of forming a Harbour at the mouth of Loe Pool, in Mount's Bay, near Helston in the County of Cornwall. Plymouth: J. B. Rowe, cited in Murphy, R. J. (1986). A Study of Loe Bar. In Cornish Studies 14:23-33.
  12. ↑ Esquiros, A. (1865). Cornwall and its Coasts. Chapman and Hall, cited in Murphy, R. J. (1986). A Study of Loe Bar. In Cornish Studies 14:23-33.
  13. ↑ Chapman, V. J. (1964). Coastal Vegetation. Pergamon Press, cited in Murphy, R. J. (1986). A Study of Loe Bar. In Cornish Studies 14:23-33.
  14. ↑ West Briton, 22 Feb., 1979, cited in Murphy, R. J. (1986). A Study of Loe Bar. In Cornish Studies 14:23-33.
  15. ↑ "Diversity of lake life is harmed by water pollution". West Briton. http://www.thisiscornwall.co.uk/Diversity-lake-life-harmed-water-pollution/story-15040203-detail/story.html. Retrieved 5 February 2012]. 
  16. ↑ Natural England. Loe Pool SSSI Designation. Accessed 28 November 2010.
  17. ↑ Gainey, P.A., Neil, C.J. and Turk, S.M. (2009) Freshwater and Terrestrial Crustacea. In CISFBR, Red Data Book for Cornwall and the Isles of Scilly. 2nd Edition. Praze-an-Beeble: Croceago Press.
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