River Faughan and Tributaries ASSI

The area is of special scientific interest because of the physical features of the river and its associated riverine flora and fauna. The River Faughan and Tributaries ASSI includes the River Faughan and its tributaries the Burntollet River, Bonds Glen and the Glenrandal River (and its tributary the Inver River). In total, the area encompasses approximately 60km of watercourse and is notable for the physical diversity and naturalness of the banks and channels, especially in the upper reaches, and the richness and naturalness of its plant and animal communities, in particular the population of Atlantic salmon, which is of international importance.The River Faughan system is entirely underlain by a range of ancient (Dalradian) metamorphosed sediments. These rocks were deformed during a major mountain building phase some 465 million years ago. Rock types are dominated by psammites and pelites – altered sandstones and mudstones. Exceptions include relatively narrow bands of altered limestone, found in the area of Bonds Glen and Park, and altered igneous rocks notably at Burntollet Bridge and south of Park.
Of particular significance are the rocks exposed in the Burntollet between Ness Wood and Burntollet Bridge. Outcrop provides excellent sections through the lower part of the Ballykelly Formation. Deformation features are also evident providing information on the alteration of these rocks. This section also contains outcrop of the altered basic igneous rock known as metabasite.

Much of the valleys occupied by the River Faughan system have been developed in glacial deposits of sand and gravel; these were formed towards the end of the last Ice Age. These typically take the form of outwash, developed as enormous quantities of glacially derived sediment was discharged from melting ice fronts. In places damming allowed pro-glacial lakes to develop with resultant flat-topped deltas forming, subsequently dissected when the ponded waters found outlets to the north.

Atlantic salmon is widely distributed in the north Atlantic Ocean. Within Europe, the species ranges from Portugal in the south to Sweden and Finland in the north. However, numbers are declining and the salmon population of the United Kingdom comprises a significant proportion of the total European stock. Although the species is still widespread in the UK, being found in several hundred rivers many of which have adult runs in excess of 1000, the latest estimates of the UK spawning population are approximately 50% down on the ten-year average.

It is estimated that the number of returning salmon entering the river system included within the ASSI is on average around 3,500, which is approximately 6% of the Northern Ireland spawning population, making the River Faughan and Tributaries one of the most important salmon rivers in the British Isles. Recent micro-satellite DNA analysis of stocks within the Foyle area (Booth, 2003) has provided evidence for population differentiation within the River Faughan catchment. The River Faughan and its tributaries are among the most productive rivers with the main run of fish occurs during the summer months and significant numbers also entering in the autumn. The River Faughan also has a considerable run of migratory sea trout.

The fish community reflects the extent and diversity of the river system. As well as salmonids, which include brown trout and Atlantic salmon, the fast-flowing waters support Brook lamprey, minnow and eel. Sea lamprey are also known to migrate into the lower reaches of the River Faughan, where the flow is less dynamic, to spawn. Downstream below this site the intertidal reach of the river also contain euryhaline (those that can survive in both salt and fresh water) and marine species such as Flounder as well as occasional visitors such as Allis Shad, Twaite Shad and smelt.The area is also important as a river habitat. In their upper catchments the River Faughan and its tributaries are all fast-flowing spate rivers with dynamic flow regimes, characterised by sequences of riffle (a shallower area with faster flowing water and larger sediments) and run (an intermediate category between pool and riffle) with occasional cascades, water falls and deep pools. Although the banks along some stretches have been modified, the channel is natural and composed of mixed substrate of boulder, cobble, gravel and pebble with scattered sections of bedrock and sandy deposits. Cobble side and point bars are occasional features. The aquatic flora in these upper catchments reflects the highly acidic character of the water, with mosses such as claw brook-moss and yellow fringe-moss and the liverwort earwort occurring on stabilised boulders and rocks. In the middle reach the vegetation remains dominated by bryophytes but now characterised by less acid loving types such as greater water-moss, river feather-moss and long-beaked water feather-moss and the liverwort St Winifrid’s moss. In the lower reaches of the River Faughan below Londonderry, where the flow is less dynamic, the bryophyte community is generally replaced by higher plants with water-starwort in the channel and stands of reed canary-grass along the banks.

The river channel of the River Faughan and its tributaries has a tree fringe along a large proportion of its length. Occasionally this fringe widens out up the valley sides to form discreet woodland blocks. In total there is more than 50ha of fragmented woodland within the site. Marginal woodland is very important to the river and its wildlife providing valuable habitat for invertebrates, birds and mammals. Trees also help to stabilise the river bank and regulate the local climate while submerged roots create a refuge for fish. Many of the insects and other invertebrates associated with the river and woodland provide food for fish and birds such as dipper and kingfisher with the latter also feeding on small fish and fry. The abundance of fish also attracts larger predators such as otter. Evidence of otter activity, in the form of spraints, is found along the length of the River Faughan and its main tributaries.

The main woodland blocks are predominantly oakwood which is acidic in nature. It can have a mixed canopy comprised of Sessile oak, downy birch, hazel, ash, alder and willows, in addition to introduced species such as beech and sycamore. Shrubs include hawthorn, holly and rowan. The ground cover is very variable. Grasses are dominant where grazing is heavy. Where the wood is less disturbed, species include wood-sorrel, herb Robert, pignut, common dog-violet and great wood-rush growing with taller ferns and thickets of bramble. In some locations where the conditions are particularly acidic bilberry forms a low field layer over a moss carpet.

Site Related Documents

Site Map (.PDF 1.51Mb), Citation and Views about Management documents (.PDF 337Kb) and

ASSI Leaflet (.PDF1.89KMb).