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  • landscape view of a river flowing through grassy fields, lined by a few trees
  • Otter on a river bank
  • The red catkins of a male black poplar
  • A close up of a pipistrelle bat

Rivers and Streams

All natural and near-natural running waters ranging from fast flowing streams to meandering rivers.

Numerous factors influence their ecological characteristics, for example geology, topography, substrate, gradient, flow rate, altitude, channel profile, climate, catchment features.

Additionally most river systems change greatly in character as they flow from their source to their mouth.

Importance for wildlife

Rivers and streams are so diverse that often the only thing they have in common is flowing water. From deeply incised stream valleys (often called gulls) to broad estuaries, they provide a huge variety of habitats and micro-habitats. They act as important wildlife corridors, connecting habitats together along their course, and are home to a wide variety of important species, including otter, water vole, water shrew, white-clawed crayfish and Desmoulin’s whorl snail.

Important associated species


  • Daubentons Bat Myotis daubentonii*
  • Soprano Pipistrelle Bat Pipistrellus pygmaeus
  • Whiskered Bat Myotis mystacinus*
  • Pipistrelle Bat Pipistrellus pipistrellus*
  • Nathusius’ Pipistrelle Bat Pipistrellus nathusii*
  • European Otter Lutra lutra
  • Water Vole Arvicola terrestris
  • Water shrew Neomys fodiens*


  • European Eel Anguilla anguilla
  • River Lamprey Lampetra fluviatilis
  • Spined Loach Cobitis taenia

Reptiles and Amphibians

  • Great Crested Newt Triturus cristatus


  • Scarce Four-dot Pin-palp Bembidion quadripustulatum


  • White-clawed Crayfish Austropotamobius pallipes


  • Norfolk or Green-eyed Hawker Aeshna isosceles


  • Crescent Moth Celaena leucostigma (riverside margins)**


Depressed River Mussel Pseudanodonta complanata

  • Desmoulin’s Whorl Snail Vertigo moulinsiana
  • Swollen Spire Snail Mercuria similis


  • Tubular Water-dropwort Oenanthe fistulosa
  • Native Black Poplar Populus nigra spp betulifolia*
  • River Water-dropwort Oenanthe fluviatilis

*Suffolk Priority species
**Priority - Research Only. Common and widespread, but rapidly declining

Factors affecting habitat in Suffolk

  • Excessive water abstraction contributes to low flows resulting in the drying out of upper sections and riparian zones, accumulation of silt and changes in the aquatic vegetation structure.
  • Physical modification of rivers, dredging and lowering river beds and confining them to specific channels for flood defence, drainage, navigation, or other purposes.
  • Pollution resulting in enrichment and de-oxygenation leading to excessive growths of blanket-weed
  • Intensive fisheries management with regular ‘weed’ cutting in the channel; fencing off and mowing strips along the bank; infilling and stabilisation of banks; and removal of unwanted fish species.

Habitat management advice

  • Maintain a mosaic of habitats such as fens, water meadows, unimproved grassland and carr nearby to increase species diversity.
  • Management plans should take into account the needs of important species. Some species found in winterbournes need a wet and dry phase over the yearly cycle.
  • Avoid works that eliminates side channels. Avoid over-abstraction that can reduce the flow of water, or cause them to dry up completely in summer, threatening mayfly populations.
  • Avoid the discharge of nutrients that promote growth of algal blooms and causes eutrophication. Avoid diffuse pollution that threatens the survival of rare species or diminishes biodiversity.
  • Steep banks and hard profiles are damaging to many aquatic species. Natural, sloping margins with soft sediment provides a greater range of suitable habitats.
  • Trampling of margins by cattle can help maintain shallow sloping profiles and areas of bare muddy ground, but avoid excessive trampling that can result in over-siltation.
  • Retain aquatic, marginal and riverbank vegetation to provide shelter and emergence sites. If fishing areas are cut in the vegetation their location should be rotated annually. Riverside trees are important to provide shelter for rare and nationally scarce species
  • Dredging should be carried out just from one side of the bank, over short stretches and in rotation to allow recolonisation. This also minimises machinery damage to the bank.
  • Naturally accumulating silt along river margins should be left. Only short sections (20-30 metres) should be cleared at a time to minimise the impact on plants and animals.
  • Retain dead wood both in and out of the water to provide niche habitats. Fallen trees can help reduce erosion of banks and slow the flow of water.

Vision for Suffolk

  1. Improve knowledge of extent and quality of rivers and streams.
  2. Maintain the existing extent of rivers and streams to ensure no net loss.
  3. Re-create rivers and streams as opportunities arise.
  4. Encourage the restoration and improvement of degraded rivers and streams.

Where to find further information


  • Sunset over the river Stour near Dedham by Nick Rowland (Flickr)
  • Otter by Natural England/Allan Drewitt (Flickr)
  • The distinctive red catkins of a male Black Poplar by Dean Morley (Flickr)
  • Pipistrelle Bat by Gilles San Martin (Flickr)