Ponds, Pools and Lochans

7. Maximising the ecological value of Sustainable Urban Drainage Systems (SUDS)

Sustainable urban drainage systems (SUDS) are increasingly being used to store and treat the surface runoff from urban areas. These systems very often include either intermittently or permanently wet ponds.

In Scotland, SEPA has identified three main objectives for SUDS schemes:

  • the prevention of damage to streams and rivers by holding and treating urban surface water run-off at or near to the source
  • the provision of additional nature conservation benefits
  • the provision of additional amenity benefits.

The general principles of the engineering design of constructed wetlands and retention ponds in Scotland are given in manuals on sustainable urban drainage systems produced by SEPA (SEPA, 1998a, b, 1999 and 2000) and CIRIA (CIRIA, 2000).

The sections below provide additional, complementary, information on the design of retention ponds and constructed wetlands which will help to maximise their value for nature conservation and improve their amenity value.

7.1 New data about the wildlife value of SUDS schemes

Advice given in the following sections is backed up by data from a recent pilot survey of Scottish SUDS ponds carried out for SEPA by Pond Action. The survey results show that:

  • SUDS ponds can, at their best, support quite rich wildlife communities largely dominated by common species.
  • Most SUDS ponds do not currently fulfil their ecological potential.
  • There are many simple design features which could be added to new SUDS schemes, or retro-fitted into existing schemes, to improve their ecological value without compromising their function (e.g. see Box 10).
  • There is a considerable worry about the number of nonnative plant species currently being introduced into SUDS sites. This includes:
    • deliberate introduction of non-native species.
    • plant suppliers who do not adequately fulfil required specifications for providing native species of local provenance.
    • accidental introduction of invasive aliens via seeds in contaminated soil from other bought-in plants. Introduction of the highly invasive New Zealand swamp stonecrop Crassula helmsii is particularly common.

Recommendations for appropriate planting of SUDS ponds are given in Section 7.5.

More specific findings from the survey are discussed in the relevant text sections below.

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