Middle Medway Catchment
Middle Medway Catchment Information
Location & Geology
The Middle Medway operational catchment covers an area of 455.94km sq from Tonbridge to Allington Lock and comprises of the Medway navigation, Alder Stream, Bid Stream, River Bourne, Ditton Stream, Hilden Brook, River Len, Leybourne Stream, Loose Stream, Mereworth Stream, Penn Stream and Tudeley Brook. For the purpose of this plan the Medway navigational catchment is management by the River Medway Alliance and the tributaries of the Medway are covered by this plan.
The catchment is a mixture of urban and rural landscapes, land use is predominantly soft fruit, orchards and hops between Maidstone and Tonbridge; whilst arable farming dominates the flatter land particularly in the floodplain.
The catchment has helped shape many of the towns and villages which the rivers and streams pass through. A legacy of mills is still evident from the small channels which split flows and the mill ponds, weirs and sluice which impound and divert most of the waterbodies across the catchment.
The catchment lies 150-200m above sea level with the water bodies obtaining flows from a mixed geology. Within the upper reaches of the catchment the east west band of Weald Clay has been overlain with alluvium and river terraces, the variability in bedrock results in different permeability with some areas heavily drained and other areas being relatively dry. As a result surface water plays a significant role in the Medway drainage.
Within the middle reaches of the catchment the junction between the Folkestone beds and clayey Sandgate beds gives rise to springs, in addition the highly fractured nature of the Hythe Beds and geological layer add to the spring flow.
The lower reaches of the catchment are characterised by Ardingly Sandstone with lower Tunbridge Wells Sands, the streams within this area have cut through these layers exposing the Wadhurst Clay. Consequently, there are many springs which coalesce to from the many streams.
Habitats & species
The catchment has high conservation potential but has experienced a long history of modification in order to sustain human activity, resulting in a catchment which has few truly natural stretches and is divorced from its floodplain. Numerous historic mill structures and many smaller impoundments are evident throughout the catchment; these pose an obstacle to migration of coarse and salmonid fish species. These structures can also result in the accumulation of silt in the impounded waters behind a structure. Both the obstruction and habitat change have consequences for river wildlife.
Habitat for wildlife varies significantly throughout the course of the catchment with good habitat disconnected by reaches of poorer quality. This is due to the impact of the many structures, and the restriction of natural hydromorphology interactions within each river. Historic land drainage practices, where natural bed material has been removed from the watercourse, has also impacted in some locations.
Non-native invasive flora species include Himalayan Balsam, Giant Hogweed, Japanese Knotweed and Floating Pennywort, non-native invasive fauna species include Mitten Crab, Signal Crayfish and Mink all of which have consequential impacts on river habitat and species.
Changing land practices within the catchment and intensive farming, highways and industry adjacent to the river can cause significant increase in the presence of silt within the river system. Diffuse pollution, surface run-off and point source pollution can be a significant risk to river habitat and a pollution incident can be damaging to both the habitat and associated species.
Lowland meadows – is characterised by species rich neutral grassland, this habitat supports a rich diversity of grasses and floral species and are important for amphibians, small mammals such as bats and birds such as barn owls. Factors affecting the habitat include intensive farming practices, reduced livestock grazing and lack of appropriate management.
Native woodland and Wet woodland – are characterised by broadleaved species, these habitat support a rich diversity of invertebrates, birds, bats and both small and large mammals. Woodland sites often comprise a range of ‘micro’ habitat types; dry woodland, wet woodland and dead wood all of which can support specialist priority species.
Standing open water – provides habitat for a variety of threatened flora and fauna, notable species include the great crested newt and water vole. The catchment supports a relatively large proportion of standing water and is rich in ponds, meres and lakes. Factors affecting the habitat include water quality, intensive management and sedimentation.
Anguilla anguilla (European eel) – Critically endangered, IUCN Red List of Threatened Species;
Arvicola terrestris (Watervole) – UKBAP Priority Species, protected by the Wildlife and Countryside Act 1981;
Austropotamobius pallipes (White clawed crayfish) – Endangered, by the IUCN Red List of Threatened Species;
Cottus gobio (Bullhead) – UKBAP Priority Species; Salmo trutta (Brown Trout) – UKBAP Priority Species
Lutra lutra (European Otter) – Near threatened, IUCN Red List of Threatened Species
Health, Recreation & Angling
The Middle Medway provides a wide range of health and recreational opportunities with easy access to the catchment from Maidstone and Tonbridge. Mote Park and Leybourne Lakes are key destinations, with many smaller open green spaces and an extensive network of Public Rights of Way providing access to the rivers. However, many of these locations have become honey-pots with resulting pressure on the natural environment. There is a growing need to create a balance between open access to the river, the natural environment and the private fishing club managed stretches of river and the private lakes, which support both coarse and fly-fishing recreation.
Heritage & Local communities
The Catchment has a rich industrial history, with numerous water mills present. In the 18th century a series of locks were installed on the River Medway between Maidstone and Tonbridge to create 19 miles of navigation, and this supported a thriving boat industry. The Medway has a long history of military and strategic importance – castles and forts became a feature of the landscape: Igtham, Leeds, and Tonbridge being a few of those most well-known.
These historic structures and landscape features have implications for the natural habitat, however the structures form an important element to the heritage and landscape of the catchment and where possible should be retained and it is necessary to find a compromise between ecological requirement and heritage.
The rural communities play an important part in shaping the appearance of the catchment that has created the distinctive landscape. The villages support thriving communities who consider the rivers to be a key element of the area and the rivers provide a focal point for many people and activities and local action will be an important part of the future of the catchment.
Flood Risk Management
The Middle Medway catchment is characterised by a diverse range of underlying soils and topographies. The very low gradient nature of many of the watercourses can result in formation of large flat floodplain areas where the rivers converge with the Medway. However, this is typically within more rural areas where the risk the considered to be lower.
The current Catchment Flood Risk Management policy for the Middle Medway will be to appropriately maintain and manage the current flood risk where it is not considered to increase significantly. However, where new challenges or information occurs, flood defence and flood risk management actions will be reviewed.
Opportunities to store water on the natural floodplain to reduce risk to local communities and natural methods of reducing surface water run-off should be considered as part of this improvement plan.