SUDS - An ecologist's view SUDS
SUDS are one of the best things for wetland habitat creation to have happened in recent years and could become comparable to the planting of woodlands and scrub along our motorways in recent years in the benefits for wildlife.
Instead of taking all the surface run-off from pavements, roofs, road surfaces via pipes direct to existing ponds streams and rivers and with all the potential present for pollution, the idea is that we take this water and either slowly filter it into the ground through permeable surfaces or transfer it to ponds and wetlands of various types (such as swales, infiltration and detention basins, retention ponds, flood storage reservoirs and wetlands) where it is cleaned and filtered prior to final discharge.
SUDS, fortunately are politically correct. No new development is complete without its proposals for sustainable drainage and engineering companies are quick to take advantage and some now specialise in this field.
This means that we are likely to see a whole new suite of ponds and wetlands associated with new urban developments, roads, landfills and other places where surface water has to be disposed off.
SUDS and Wildlife
However, if SUDS are not to be wholly engineering features, thought needs to be put into how they can best be adapted for wildlife.
As all nature reserve managers know, you cannot simply create a habitat and leave it to its own devices.
To use SUDS for wildlife, you need:
appropriate ecological design
construction that strictly uses that design
management to keep the whole thing working, and finally
monitoring to ensure that it is really doing its job.
Some problems
This is not nearly as easy as it seems. Few engineering companies have ecologists with wetland wildlife experience on their team. Few construction site managers are knowledgeable about the intricacies of ecological design and will be relying on an engineering drawing to get the layout and levels correct.
Even if all appears in order, you still have the man on the machine to contend with. The excavator operator and his foreman will have a pride in their job and if all the surfaces are not smoothly graded and neat and tidy, they feel they will have failed and will be laughed at by their co-workers.
And then, finally you have your ecologically designed and constructed site. What now? Where will all the wetland and marginal plants come from, how will they be planted and critically who will look after the whole caboodle? Will it be the management company, English Nature, the Environment Agency, the developers, the water company, the local authority countryside section, the Highways Agency, or even perhaps local volunteers?
In critical engineering locations such as along major roads, SUDS are maintained along with bridges and other features. On small housing developments (for instance), who will manage and maintain the SUDs is far from clear.
Indeed, the provision of new wildlife habitat is one of the major features of many SUDS schemes, but how many such schemes have an ecological design input, are supervised by ecologists during creation and after.
Making SUDS suitable for wildlife
- Firstly, ensure that each SUDS has an ecological basis for their design and that there is a mechanism for supervision, aftercare and continuing management for wildlife conservation.
- Appreciate that SUDS can provide for local biodiversity and contribute to Biodiversity Action Plan targets.
- Ensure that wetlands are of appropriate and variable depths, are in the open (not below woodland or squeezed between trees) and that they have soft substrates suitable for rooting and have varied margins and islands to ensure a wide range of micro-habitats that are so essential for ecological sustainability.
- Basins and Ponds are the main component of SUDS that can be adapted for wildlife.
- Balancing ponds and flood storage reservoirs only hold water temporarily and so need enhancing as wildlife features such as by ensuring they have some deeper areas where water is retained for longer and so creating ecologically diverse ephemeral wetland features.
- Lagoons provide still conditions for settlement and can be modified for wildlife by ensuring that they have vegetated margins.
- Retention Ponds detain water for longer periods and so can be managed as ephemeral wildlife ponds.
Wetlands have the greatest potential for wildlife, especially if other features in the SUDS chain are also managed for wildlife. Ensure that the planting scheme is appropriate for the locality and preferably have a local source for the plants available.
Water Chemistry
Be careful to get your water chemistry correct. Water arising off urban areas will be rich in calcium bicarbonate and is generally alkaline. This is fine if your final outfall is to such an area, but not if discharge is to an acidic habitat. Putting calcareous water into an acidic valley mire is almost as bad as putting toxic substances into the water. The acidic habitat will decline and be replaced with wetland habitat lacking in diversity, in all the plant and animal communities that require acidic nutrient poor conditions.
Be careful, because while SUDS can create wetlands, they can also cause the serious decline of existing specialist and more valuable habitats.
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