Chalk Rivers

Chalk Rivers - John Miller - Explore Kent

Current Status

England has the principal resource of chalk rivers in Europe. They are all located in south and east England - from Dorset to East Yorkshire. Kent's chalk rivers arise from the North Downs chalk and include the Darent, Cray, Shuttle, Dour, Nailbourne and stretches of the Great Stour, Little Stour and North Stream. However, unlike some chalk rivers in other counties, none of Kent's currently qualify for statutory conservation designation. However, some key stretches in Kent such as the Great Stour between Wye and Canterbury have been designated as non-statutory county ‘Wildlife Sites' (or SNCIs) by the Kent Wildlife Trust.

Chalk rivers have a characteristic plant community, often dominated in mid-channel by river water crowfoot and starworts, and along the edges by watercress and lesser water-parsnip. They have low banks that support a range of water-loving plants.

All chalk rivers are fed from groundwater aquifers, producing clear waters and a generally stable flow and temperature regime. These are conditions which support a rich diversity of invertebrate life and important game fisheries, notably for brown trout and salmon. Brook lamprey, white-clawed crayfish and otter are among the internationally important species which chalk rivers support. Other, nationally threatened species such as the rapidly-declining water vole are also characteristic of chalk rivers.

Most chalk rivers have 'winterbourne' stretches in their headwaters. These often run dry, or partially dry, in late summer because of lack of rainfall recharging the aquifer. A characteristic range of invertebrates are adapted to these conditions, as is the brook water crowfoot.

Factors

  • Excessive abstraction mainly for public water supply from the chalk aquifer has contributed to low flows on a number of chalk rivers. This has led not only to drying out of upper sections and riparian zones, but also to reduced flow velocities, accumulation of silt and changes in the aquatic vegetation structure.
  • Physical modification: usually for flood defence, drainage, navigation, historic water-mills, ornamental or fishery purposes. These changes often lead to a marked reduction in river habitat diversity, and reduced ecological connectivity along the river's course.
  • Pollution: In common with most lowland rivers, chalk rivers are significantly affected by sewage discharges, and in times of low flow de-oxygenation may occur. Effluent from fish farms, water-cress beds and light industry can have similar effects. Agricultural practices can lead to diffuse pollution and increased silt inputs.
  • Fisheries management can be beneficial, neutral or detrimental in its effects.

Current Action

*In carrying out their functions the Environment Agency, Water Companies, Internal Drainage Bodies, Local Authorities, in England and Wales have a statutory duty to further conservation where consistent with purposes of enactment relating to their water management functions. On-going work includes addressing the causes and impacts of low flows and ensuring that flood defence activity and development are sympathetic to the needs of chalk river habitats. *Multi-organisation countryside and river management partnerships exist in most of Kent's chalk river catchments, with remits to enhance chalk river habitat where appropriate. Examples include the Kentish Stour Countryside Project, the River Dour Steering Group and the North-West Kent Countryside Project. *The Environment Agency's Integrated Water Management Strategy project is addressing the potential impact on the Great Stour of the development of Ashford.

Objectives

  1. Conserve the characteristic flora, fauna and physical habitat features of chalk rivers including their winterbourne stretches.
  2. Review the need and potential for restoration of flows, water quality and habitat diversity of Kents chalk rivers in consultation with local communities and organisations, and implement restoration where appropriate.
  3. Raise awareness of the importance of Chalk Rivers as a UK priority habitat in Kent.

Relevant Habitat Action Plans

The relevant UK Habitat Action Plans:

The relevant UK Species Action Plans:

The relevant Kent Habitat Action Plans:

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