Home River Estuary Offshore Habitat Map References

The content of this website contains the personal opinions of the members of group 12 only,

and is not the opinion of the University of Southampton or the National Oceanography Centre

Southampton.

Falmouth 2017 - Group 12 7TITLE

Gallery

Truro river is one 6 main tributaries that eventually flow with The Fal into the estuary, moreover 28 minor creeks and rivers run into the estuary. The River Fal starts at Goss Moor and runs for around 18km before reaching the ocean, reaching depths of 34m. This, combined with a width of at least a mile at all points in the estuary, make the Fal estuary the 3rd largest natural harbour in the world. The shoreline stretches 127km, at Falmouth is a macrotidal system with a maximum spring tide of 5.3m and at Truro there is a mesotidal system with a spring tide of 3.5m. The outer tidal basin is colloquially known as Carrick Roads and forms about 80% of the main water body of the estuary; the total area is 24.8km2, of which 17.36 km2 is subtidal, 6.53km2 is intertidal mudflat and 0.93km2 is saltmarsh. The channel becomes progressively shallower as it progresses inland ranging from 34m to 5m at King Harry’s Reach

The Wheal Jane mining incident affected Fal Estuary in 1992, January 13th when 50 million tonnes of acidic (pH 3.1) metal laden water was accidentally released into the estuary due to pumping being stopped for technical reasons. This is currently being managed by an active treatment plant which during its first full winter season of operation treated in total 4400 million gallons of water.

Fal and Helford is a Special Area of Conservation (SAC) due to the following habitats and interest features: Large shallow inlets and bays; Estuaries; Subtidal sandbank; Intertidal mudflats; Saltmarsh; and Reefs.

Over the last 10000 years, the Holocene period, sea levels initially rose quite rapidly at about 1m per century drowning the river valleys to form the estuary – in the latter part of the Holocene the sea level decreased to about 0.1m per century such that the rate of the sediment supply outpaced the rate of sea level rise so that the upper parts of the estuary started to infill with sediment creating an apparent sea level fall; this type of flooded valley system is referred to as a ria (defined as an inlet formed by partial submergence of unglaciated river valleys Bird, 2000). Fal and helford SAC encompasses the two rias (drowned river valleys) of the Fal estuary and the Helford River and the inner part of Falmouth bay, giving rise to its sinuous shape. These give rise to a range of habitats from very sheltered mudflats in the upper Fal, to rocky, wave-exposed coasts such as found in the mouth of the Helford River. There is very low freshwater input into either estuary leading to all habitats, unusually, being fully marine. In particular there are rare rocky areas on the Falmouth bay coastline providing a habitat for rarer marine animals. Falmouth bay is protected from prevailing South Westerly winds despite its relative shallow depth and exposed location on the South Cornwall coast.

We analysed nitrate, phosphate, silicate, chlorophyll and oxygen present and physically, temperature and salinity were monitored both offshore, in the estuary and in the river. Devonian metasedimentary rock dominates the geology of the Fal Estuary.