River Dee (England)

Also within

Cheshire CountyClwyd CountyShropshire County

Condition (Natural England)

Climate exposure

This is about exposure to a nationwide pressure this habitat type carries — not a verdict on this site's own management.

Habitats

Fast flowing river and stream

Geology & landscape

Geological Period: Quaternary

Landscape processes: Coastal, Fluvial, Glacial

Birds & fish recorded

Birds

Fish

Description

Description The River Dee is notified for its nationally important transition through a range of river types from mesotrophic to eutrophic. It is also notified for Atlantic salmon Salmo salar, otter Lutra lutra, club tailed dragonfly Gomphus vulgatissimus and fluvial geomorphology. The River Dee lies within both England and Wales and is notified as separate SSSIs –the River Dee England and the Afon Dyfrdwy River Dee SSSI in Wales. The features for which the two SSSIs are notified, in particular the range of river types and migratory fish, depend upon the whole river ecosystem. The fluvial geomorphological interest occurs in both England and Wales. The English sections of the river are therefore notified as components of the whole ecosystem for which the river is a nationally important example and because the otter, club tailed dragonfly and the geomorphological interest occurs on the English reaches. General description The River Dee England SSSI comprises the part of the river of the same name and the part of its tributary, the Ceiriog, that flow through England. The site includes a section of the river as it meanders across the Cheshire plain down stream from Shocklach, where it forms the national boundary, northwards through Chester to the city’s western outskirts. Further up the catchment, the southern half of river channel of the River Ceiriog located in North Shropshire between Chirk Castle and Erbistock forms part of the SSSI. The Afon Dyfrdwy River Dee SSSI has its source in Snowdonia at the outflow of Llyn Tegid SSSI and it includes the Ceiriog, Meloch, Tryweryn and Mynach tributaries. Its catchment contains a wide spectrum of landscape from high mountains around Bala, rugged peaks near Llangollen, steep sided wooded valleys and the plains of Cheshire and North Shropshire through to the vast mud flats of the estuary. There is a tidal influence as far upstream as Farndon and high tides regularly exceed the Chester weir crest level. It flows through broad valley near Corwen and through the spectacular Vale of Llangollen before meandering northwards through parts of the Cheshire plain where it joins the River Dee England SSSI. Further downstream it includes the stretch below Chester to where the river meets the Dee Estuary. The River Dee is reputed to be the most regulated river in Europe, with flow controlled by the reservoirs of Tegid, Celyn and Brenig. Flora The River Dee England is typical of a mesotrophic river. The aquatic plant community includes species of water crowfoot Ranunculus fluitans x aquatilis and Ranunculus peltatus and also floating water plantain Luronium natans. Water crowfoot forms extensive beds along the whole length of the Dee where flow conditions are suitable. Other aquatic plants which occur within the site include intermediate water starwort Callitriche brutia ssp. hamulata, alternate flowered water milfoil Myriophyllum alterniflorum and bryophytes including Rhyncostegium riparioides and Fontinalis antipyretica. Marginal vegetation consists mainly of reed canary grass Phalaris arundinacea with occasional branched bur reed Sparganium erectum. Downstream of Llangollen to Bangor on Dee the river shows signs of nutrient enrichment with Canadian waterweed Elodea canadensis becoming more prevalent. Below Bangor on Dee the River Dee England flows into the Cheshire plains and displays typical characteristics of lowland river types with shallow gradients and rich geology, with curled pondweed Potamogeton crispus and fennel pondweed Potamogeton pectinatus occurring frequently. There is good tree cover along the banks of the River Dee and the tributaries, with the Ceiriog being tree lined on both banks along much of its length. The dominant species are alder Alnus glutinosa and willow Salix spp., with occasional ash Fraxinus excelsior and oak Quercus spp.. Where sections of the river bank have been fenced off the vegetation tends to be dominated by bramble Rubus fruticosus, nettles Urtica dioica and other tall ruderals. Himalayan balsam Impatiens glandulifera and Japanese knotweed Fallopia japonica are increasing throughout the site. Mammals The otter Lutra lutra is well established throughout the river system, especially where appropriate bank side cover exists. Numbers have increased along the River Dee England in recent years and there is a record of young being seen in 2000. water vole Arvicola amphibius have been recorded on the middle and lower reaches of the River Dee. Fish The River Dee is recognised as one of North Wales’ premier rivers for Atlantic salmon Salmo sala. The Mynach, Meloch and Ceiriog tributaries are the most important salmon spawning tributaries in the Dee catchment and are included in the Afon Dyfrdwy River Dee SSSI and also in relation to the English part of Ceiriog in the River Dee England. Other migratory fish utilising the river system include sea trout Salmo trutta trutta, eel Anguilla anguilla, river lamprey Lampetra fluviatilis and sea lamprey Petromyzon marinus. Smelt Osmerus eperlanus and twaite shad Alosa fallax have been recorded in the section between Chester and the estuary. The Dee also supports important populations of non migratory fish including brown trout Salmo trutta, bullhead Cottus gobio and brook lamprey Lampetra planeri. The middle and lower reaches of the Dee support a diverse coarse fish population. The river is noted for its grayling Thymallus thymallus. Birds The entire River Dee system and associated tributaries support a wide range of breeding birds, which utilise a variety of bankside habitats. Nesting habitat for the kingfisher Alcedo atthis and sand martin Riparia riparia is provided by active erosion of river banks. Areas of fast flowing water and bankside cover are favoured by the dipper Cinclus cinclus and grey wagtail Motacilla cinerea, whereas the yellow wagtail Motacilla flava and mute swan Cygnus olor are found along the slower flowing reaches. Populations of grey heron Ardea cinerea, common sandpiper Actitis hypoleucos and goosander Mergus merganser also occur on the River Dee. Areas of the Lower Dee flood plains provide breeding grounds for waders such as the lapwing Vanellus vanellus, and, when flooded, provide important over wintering sites for the pintail Anas acuta. Invertebrates The club tailed dragonfly Gomphus vulgatissimus is nationally scarce and present along the lower Dee including several parts of the River Dee England, particularly where the river is slow flowing and there is adjacent woodland habitat or bankside tree cover available for adults. This population is the most northerly in Britain and the only one within the Cheshire Area of Search. The lower reaches of the River Dee support Britain’s only known population of the stonefly Isogenus nubecula, which is classified as vulnerable in the Red Data Book The nationally scarce weevil Baris lepidii has been recorded on sandy river banks along the lower Dee but has not been recorded on any other Welsh river. Geology / Geomorphology The River Dee Holt to Worthenbury Geological Conservation Review GCR, previously notified as an SSSI, straddles the border and is partly located within the River Dee England SSSI and the Afon Dyfrdwy River Dee SSSI. Holt to Worthenbury Fluvial Geomorphology This area of interest comprises a meandering reach of the River Dee between Holt in the north and Worthenbury in the south. It includes land in Wrexham Wales and Cheshire England and consists of some of the most spectacular and intricately developed river bends or meanders seen anywhere in Britain. The area is of national importance for studies of fluvial geomorphology. The main features of interest within the area are: 1. the present river channel and its intricate pattern of meanders; 2. the main areas of flood plain either side of the river, for the full length of the selected reach; 3. all the visible palaeochannels abandoned channels located on the flood plain adjacent to the present channel; 4. the gravel and sand bars located within the modern channel and the other evidence of modern day river processes contained within the channel; and 5. the most impressive of the remnants of ancient cliffs located towards the north east and south west margins of the site. The scientific value of the site can be summarised as follows, First, the pattern and scale of the meanders are exceptional on a British scale, the range of forms from simple curves to double headed forms and the intricacy of the pattern developed over the whole reach is outstanding. Second, the total landform assemblage, including the remnants of ancient river cliffs, the flood plain areas and the present and abandoned channels, provides the basis for reconstructing the development of the river since the end of the last glaciation. Third, the abandoned channels and old meander loops some of which were once oxbow lakes are exceptional landforms in their own right; their pattern, location and contained sediments provide significant potential for reconstructing some of the geologically recent changes in the course of the River Dee in its long evolution during Holocene times, i.e. the last 11,500 years. Fourth, the gravel and sand bars distributed along the course of the modern channel and the changing form of its banks and bed, bear witness to a range of important modern day fluvial processes. Although this part of the course of the River Dee has changed in position markedly during the Holocene, the last few hundred years have been characterised by relative channel stability. It seems likely that the banks and bed of the modern channel are now evolving in response to changing flow and sediment regimes induced by upstream regulation and other human modifications to the fluvial system. The significance of the site for studying modern day river processes is enhanced by the tidally influenced downstream reach. This renders the area potentially significant for investigating the effects of possible future sea level rise on the development of the river channel, particularly in view of the long history of tidal influence and stage records river level at downstream locations. This reach of the Dee is therefore of major scientific importance and, as such, is a valuable part of the heritage of great Britain. Its national importance stems from its outstanding combination of landform, sedimentary and process evidence. Most large British rivers have been significantly channelised or straightened in their lower reaches. The Dee is exceptional in maintaining an extremely sinuous planform across the sensitive fluvial tidal transition zone. Other information The River Dee England abuts Afon Dyfrdwy River Dee SSSI The Afon Dyfrdwy River Dee proposed SAC abuts onto the Dee Estuary SAC. The River Dee England SSSI in association with the Afon Dyfrdwy River Dee SSSIsupports the following habitats and species listed in the EC Directive 92/43/ EEC on the Conservation of Natural Habitats and of Wild Fauna and Flora. Those marked with an asterisk occur within England, Floating vegetation of Ranunculus of plane, sub mountainous rivers – Annex I Otter Lutra lutra* Annex II and IV Sea Lamprey Petromyzon marinus* Annex II River Lamprey Lampetra fluviatilis * Annex II and V Brook lamprey Lampetra planeri* Annex II Atlantic salmon Salmo salar* Annex II and V Bullhead Cottus gobio* Annex II Freshwater pearl mussel Margaritifera margaritifera – Annex II and V grayling Thymallus thymallus – Annex V The otter Lutra lutra and the Freshwater pearl mussel Margaritifera margaritiferare listed under Schedule 5 of the Wildlife and Countryside Act 1981 as amended. Parts of this site have been selected as a result of the former Nature Conservancy Council’s Geological Conservation Review Gregory, K. J. 1997. Fluvial Geomorphology of great Britain. Geological Conservation Review Series No. 13., Chapman and Hall, a national survey and evaluation of sites of geological and geomorphological interest. The River Dee England lies within the Meres and Mosses and Oswestry Uplands Natural Areas.

Species mentioned

Plant communities