| Rivers, Streams & Associated Habitats Action Plan - Gloucestershire |
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| Extent/Distribution Gloucestershire is estimated to have 5284 km of watercourse, a widespread and important resource. They vary in character and quality from rivers of international importance such as the Wye, designated as an SSSI and candidate SAC, to those which have been degraded and constrained by river engineering and development. The variety of features found in rivers and streams support a diverse range of plants and animals. Gloucestershire’s rivers support many threatened species including otters, water voles, allis and twaite shad, white-clawed crayfish and the depressed river mussel. The wider catchment includes extensive ditch systems which complement the rivers and streams wetland resource in Gloucestershire. In some instances they can provide a refuge for species when other wetland habitats become unsuitable. Water voles for example are shown to be reliant on ditches especially as they are now missing from many of the more major rivers and streams in the county. Rivers and streams in Gloucestershire’s Natural Areas There are three main catchments into which all Gloucestershire’s Rivers and Streams flow: the Lower Severn; the Lower Wye and the Upper Thames. The physical character of rivers is strongly influenced by geology, landscape and land use in terms of factors such as channel slope, size, flow type and associated habitat diversity. As a result there is a strong relationship between river type and Natural Areas. The watercourses found in the different Natural Areas in the county are as follows: Cotswolds: Rivers: Churn, Coln, Windrush, Dikler, Eye, Sherborne Brook, Leach, Evenlode; (Upper Thames catchment) Frome, Slad Brook, Painswick Brook, Isbourne (Lower Severn Catchment) Cotswold streams generally have a high water quality supporting a diverse range of aquatic life and as a result hold species such as the white-clawed crayfish, caddis flies and the dipper, indicative of high quality streams. This Natural Area is a key area for otter recolonisation into southern England, water vole populations and white-clawed crayfish. The Dikler, Churn and Coln are important for water voles. The River Windrush falls into the Upper Thames Tributaries ESA. Thames and Avon Vales Rivers: Thames, Coln, Churn, Ampney Brook (Upper Thames Catchment) The source of the Thames is in the Natural Area and all of the Rivers in this Natural Area eventually flow into the River Thames. These Rivers all flow through the Cotswold Water Park and so link up with the various wetland habitats found there. Severn and Avon Vales: Rivers: Severn, Avon, Cam, Wicksters Brook, Little Avon River, Swilgate, Leadon, Chelt (Lower Severn Catchment ). The River Severn is the major Gloucestershire River in this Natural Area. In Gloucestershire it flows through a broad flat floodplain, the natural character of which has been altered through the construction of weirs and locks and much of the river is impounded. In places this has created barriers for the movement of fish populations and has isolated or reduced their gravel spawning grounds (e.g. for salmon and shads). The Severn Vale has extensive ditch/rhine systems associated with the washlands and the hams. Where these have naturally or artificially maintained high spring and summer water levels they provide valuable wildlife habitats, particularly for invertebrates. Stretches of the Rivers Leadon, Frome and Little Avon are designated as salmon fisheries under the EC Fisheries Directive. Stretches of the Rivers Severn and Cannop brook are designated cyprinid fisheries under this directive. Wicksters Brook, a tributary of the River Cam is particularly important for water voles. Dean Plateau and Wye Valley: Rivers: Wye; (several smaller brooks such as Cinderford Brook, Cannop Brook and Ell Brook drain the central Dean plateau and flow into the Wye or the Severn). The River Wye forms the Western Boundary of this Natural Area and is one of the most significant features. The Wye is notified as a SSSI and is also identified as a cSAC (candidate Special Area of Conservation) as it is regarded as an internationally important river system. It holds populations of many threatened species including the BAP priority species twaite and allis Shad, white-clawed crayfish, otter and the rare freshwater pearl mussel. The Wye has a very rich invertebrate fauna. 29 fish species have been recorded in the River Wye and its tributaries. Migratory fish such as salmon, river and sea lamprey and allis and twaite shad are particularly important. The combination of relatively good water quality and rich and diverse in-river and bankside habitats enables the river to support such a wide range of fish species. The tidal and the saline influence of the Lower Wye is evident past Brockweir. Water quality Water quality is adversely affected by direct and diffuse pollution from industrial, domestic and agricultural sources. Some watercourses, of poor water quality through sewage inputs, include tributaries of the Leadon and a stretch of the Chelt downstream of Cheltenham. Some streams in the Forest of Dean (such as Cannop brook and the River Lyd) receive minewaters from abandoned coal mines. Diffuse pollution from agriculture through pesticides, fertilizers and soil erosion has been identified as having a significant effect on water quality in the River Wye cSAC and is probably a widespread issue affecting many, if not most lowland river systems. Damage and disturbance to soil from livestock, cultivation and machinery can cause sediment laden water to enter watercourses. Farmers are becoming more aware of the potential risks of diffuse pollution, the use of buffer zones, for example, are being promoted. Water resource management Excessive ground and surface water abstraction for domestic, industrial and agricultural purposes can result in excessive reduction in low summer flows. Low flows affect a number of watercourses; in the Leadon catchment, for example, flows in the Ell Brook, the Red brook and the Peacock Brook drop rapidly during dry summer months. Although there are mechanisms to control this there are problems with historic licenses of right. This is exacerbated by illegal abstractions and natural drought. In low flow conditions pollutants are insufficiently diluted. There has been concern over many years regarding the impact of groundwater abstraction on the Cotswold tributaries of the Thames, particularly the River Churn and Ampney Brook. Flows in the rivers Frome and Leadon may be affected by Restoration Trusts who are working to restore two long abandoned canals (the Stroudwater/Thames Severn canals and the Herefordshire and Gloucestershire Canal). This however, should not be a problem if the right safeguards are in place. The River Wye is influenced by the release of water from reservoirs in the headwaters of the river, in accordance with a regulation order. Inappropriate catchment/riparian management Loss or degradation of floodplain, valley or river corridor habitats reduces the value of watercourses for wildlife. A watercourse constrained by development does not have sufficient space for the natural processes of erosion and deposition; flooding might have to be controlled and there maybe no buffer between development and the water environment. Agricultural intensification has resulted in the erosion of wildlife habitats in floodplains and river corridors. Culverting can result in the loss of lengths of open watercourse. Culverting isolates stretches of watercourse and presents a barrier to the free movement of wildlife through a catchment. Unsympathetic development can result in a loss of riparian habitats. Development also leads to the creation of large impermeable surfaces which drain into piped drainage systems. As a result, natural infiltration into the ground is reduced with a corresponding reduction in ground water and surface water recharge, artificially high flood peaks or flash flows, low dry weather flow and diffuse urban pollution. Many Gloucestershire watercourses have less tree cover than is desirable and bankside trees such as old willow pollards are often managed unsympathetically. Unsympathetic management of bankside habitat includes over grazing and cultivation right up to river edge. Engineering and regulation Most watercourses have been modified to some degree by drainage or flood defence engineering or maintenance improvements. These modifications include channel dredging and the modification of instream features such as gravel bars, islands, oxbows, pools and riffles (the natural flooding regimes of many rivers sustain wetlands of ecological importance e.g. Ashleworth Ham). Navigational improvements have had similar effects on the Severn. Unregulated works to river banks to prevent soil erosion may also affect the naturalness and wildlife features of rivers (e.g. the loss of sand martin banks). The natural character and flow regime of many rivers has been reduced by the impact of impoundment structures such as weirs, locks, flow measuring stations, hydro-electric power schemes or reservoirs such as Lake Vrnwy on the Severn. This can affect the size and frequency of flood plain inundation, the mobility of fish populations, river habitat quality and cause the loss or isolation of gravel spawning grounds. Many of these structures and features are however of cultural, landscape or flood defence significance. Invasive species Alien populations of species such as mink, zander and signal crayfish have damaging effects on vulnerable native species. Japanese Knotweed, Giant hogweed and Himalayan Balsam can suppress native river bank plants. Still waters including ditches and canals are at risk from aquatic plants such as Australian Stonecrop Crassula helmsi and Water fern Azolla filiculoides. Increased recreational use Recreational activities such as boating, water sports or angling can disturb wildlife and damage can be caused to marginal or bankside vegetation for example from boat wash or trampling and through associated development such as slipways and launch points. In much of the county however these uses complement conservation needs by ensuring that open attractive corridors are maintained along watercourses and sometimes providing resources for management. Angling may in some instances lead to the stocking of inappropriate fish in watercourses and the transmission of pathogens such as crayfish plague. Overfishing may also be a problem. The stocks of some migratory fish species, especially salmon and elver stocks are thought to be declining significantly. External influences on rivers Factors operating at a wider catchment or even global scale can have impacts on the wildlife of rivers. Acidification of headwaters affect some migratory fish species; climate change may affect the movement of migratory fish; fisheries outside rivers (e.g. nets, fixed engines, at sea catch) may reduce fish populations in rivers. To gain a better knowledge of the biodiversity of river, stream and
riparian habitats in To raise awareness, understanding and education about the functions
and value of the { targets} {Current action} Policy and legislation [policy]Management
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