ABSTRACT
The ecosystem services available through the application of sustainable urban drainage systems (SUDS) are well understood in terms of the provision of water management functions, both quantity and quality; and ecology and amenity resources (CIRIA 2007). However, the development of these systems has, in many countries, been very limited. For example, the twenty-sixth report of the Royal Commission on Environmental Pollution, ‘The Urban Environment’ (2007) stressed the need in the United Kingdom for changes in practice, legislation and guidance to encourage the use of such systems for the benefit of urban communities. Only a matter of months later the low level of implementation of SUDS contributed to the scale of impact from unprecedented and devastating flooding in parts of England. The report produced in response to these floods, the Pitt Review (2008), clearly identified that the lack of effective surface water management systems, such as SUDS, exacerbated the level of damage and associated costs of the flooding. Significantly, the Pitt Review highlighted the lack of clear ownership and responsibility for SUDS as a key reason for their limited adoption and that by addressing this one factor the wider use of SUDS would be supported. The momentum and culture to use SUDS (referred to as Best Management Practices in Scotland and the USA and Water Sensitive Urban Design in Australia) is slowly recognising that urban water management for dealing with flooding and runoff quality does not have to occur at the cost of ecological potential. In Seattle, programmes for urban stormwater management have integrated SUDS that have a key target of benefiting the ecological and nature conservation value of the urban greenspace (Johnson and Staeheli 2006). In the United Kingdom, SUDS development so far has been driven by flood management and water quality with biodiversity playing a peripheral, almost incidental gain to a particular scheme (Worrall 2007). However, SUDS that embrace ecology at an early stage and with a deterministic role in the design are likely to be more robust and provide optimum benefits to the local and wider community (Everard 2002). SUDS using habitats as integral features include green roofs, grass swales, detention ponds, wetlands, marshes and reedbeds. Each of these features may play a role in regulating and storing storm flow, improving urban runoff quality and providing nature conservation and landscape opportunities. Often, if an ecologist is consulted on a SUDS project it will be to specify the types of plant species to be used. This seemingly simple task is, however, critical to the success and
long-term functionality of most habitat-based SUDS. In Australia and the USA concerns have been expressed about the ‘failure’ of wetland SUDS because of the use of inappropriate plants which are not able to tolerate the ‘dynamic nature of urban hydrology’ (abstract from Greenway et al. 2006). Therefore, a critical role of an ecological approach in the development of SUDS is to define the species and habitat structures that address the essential prerequisite of such systems, i.e. to be sustainable. To embark on this process there are three basic questions to be asked:
• Which plants would be viable in response to the hydrometric and water quality character of the site?
