Stormwater management measures take many forms and can often be directed at addressing specific problems. In most instances, a number of management measures can be implemented in series or concurrently forming a treatment train approach to stormwater management. The correct utilisation of the various components of the treatment train is a vital design consideration and requires a holistic approach to their performance specifications and positions in the treatment train. An overview of common structural elements of the stormwater treatment train, together with their target pollutant particle range and operating hydraulic loading range is shown in Figure 1.
Figure 1. Stormwater Quality Improvement Measures, Target Particle Size Range and Operating Hydraulic Loading Range (Wong & Breen, 1999).
In built-up catchments, the development of the stormwater management strategy will need to address existing stormwater-related problems as well as providing the framework for sound practices in future development or re-development of the catchment. The fundamental factor underpinning the success of the stormwater management strategy is information on the current state of the catchment. This information primarily relates to:-
- causes and effects of degradation of the aquatic environment, including the severity of the effect and future "do-nothing" scenario;
- "land capability" in terms of suitability for the different types of management measures to address the problem.
In addition to examination of existing problems, data related to potential future activities will allow anticipated problems to be highlighted and thereby provide the basis for non-structural management measures to be formulated as part of the planning process.
Each of the identified and anticipated problems will need to be evaluated to define their severity and significance at the regional and local level to allow the ranking of these problems. A risk analysis approach may be used to assist with prioritisation of the stormwater-related problems identified.
Structural and non-structural management measures, used individually or as part of a chain of treatment measures, can then be formulated to mitigate the effects of the existing and anticipated problems identified. The merits of these management measures can then be assessed against the various management objectives using MUSIC.