LARGEST --Tidal Lagoon in Britain, The Fleet - Weymouth
Posted by: 
elrecke
N 50° 36.407 W 002° 30.788
30U E 534451 N 5606212
The Fleet, caught between the sea and the shingle bank of Chesil beach, is the largest tidal lagoon of its kind in Britain.
Waymark Code: WMAD7Z
Location: South West England, United Kingdom
Date Posted: 12/30/2010
Views: 3
In General
The Fleet Lagoon is a shallow area of saline water between Chesil Beach and the mainland. It is 13 km long. Its width varies from 900 metres at Littlesea down to just 65 metres in the Narrows. The deepest part is 4-5 metres deep, but all of the mid and upper Fleet is less than 2 metres deep.
The lagoon is an important area for wildlife with a number of national and international designations to help protect this important area. The area lies at the centre of the Jurassic Coast, a UNESCO designated World Heritage Site.
Lagoon Forming
The Fleet lagoon was formed when Chesil Beach moved onshore as the sea levels rose. In the past it was much larger than it is today. The Fleet is 13.1 km (8.2 miles) long and covers an area of 480 hectares. The width varies from 900 metres at Littlesea down to just 65 metres at The Narrows. The deepest part is in the lower Fleet where it is 4-5 metres deep. Most of the upper Fleet above The Narrows is no more than 2 metres deep.
Tidal Conditions
The Fleet connects to the sea via a narrow channel at Ferrybridge into Portland Harbour. Sea water can also enter the Fleet by percolation through Chesil Beach under some tidal conditions. Fresh water can enter the Fleet from a number of small streams and by run-off from the surrounding fields. Under storm conditions water from Lyme Bay can come through and over Chesil Beach in sufficient quantities to make the pebbles highly mobile and voids form in the Fleet side of the beach called canns. Cann events happen during south-westerly gales most winters but are usual minor events in which existing canns become re-established. Major cann events are less frequent, happening roughly every 10-15 years. The last major cann event was in 1990.
Water Temperature
The water in the Fleet is generally warmer than the surrounding sea in the summer and cooler in the winter. The temperature in the lower Fleet can vary by up to 4ºC during a twelve hour tidal cycle.
Designations
The Fleet is an important area for wildlife and has received the following designations:
* Special Area of Conservation (SAC)
* Special Protection Area (SPA) under the EU Birds Directive
* A Ramsar site
* Site of Special Scientific Interest (SSSI)
* Designated bass nursery area
Source:
chesilbeach.org