Without storm water management of our urban areas, flooding would affect the lives of citizens living, working and moving through these areas, and prevent the movement of goods and information. Storm water should not be considered a threat, however, but rather as a positive landscape element. Together with vegetation, it constitutes protective temperature islands in cities. Also, in daily speech this approach is called sponge city.
In recent years, conventional “hard engineering” approaches (sewers etc.) have been complemented – and in some cases replaced – with more natural approaches using blue-green infrastructure. This can involve, for example, a system of measures such as green belts, grassed dry retention ponds or raingardens. Integrated master planning and modelling has also become a key part of storm water management in urban areas.
Sustainable storm water management schemes must be integrated design solutions, involving a set of measures suitable to specific local conditions. Such an integrated storm water system has not only to consider and manage storm water in present climatic conditions, but also all potential future climate change scenarios (e.g. more intense rain events, less rain, rising temperatures etc.).
Comprehensive long-term planning for storm water is crucial and should involve integrated designs utilising various innovative technical solutions, including blue-green infrastructure.
There are three basic recommended stages to be taken when managing storm water in urbanised areas:
- The first step is based on the idea of keeping storm water where if falls and retaining it locally.
- If the amount of water is too great for local retention, then in the second step it is necessary to store storm water in extra storage capacity – either naturally or artificially created.
- Excess storm water that cannot be retained or stored has to be, in a third step, slowly drained through available or created waterways.
From the point of view of key stakeholders including states, communities, business/industry groups, academia and non-governmental organisations, the overall process should rely on adopting a long-term approach to planning. Communities can also elaborate plans that allow for the integration of selected projects within other community development plans, including master plans.
With an effective participation strategy, guidance and public education, local communities have the opportunity to learn, ask questions, raise issues, and ultimately ensure Sustainable Drainage System (SuDS) implementation benefits communities in the best possible manner.
The financial case for suds and blue-green infrastructure
SuDS are sometimes incorrectly viewed as being more expensive than conventional storm water management. This misconception comes from too narrow a focus on investment costs for projects in city centres.
On the contrary, they are usually more cost effective than conventional methods, and they also bring additional multiple benefits. Experiences from the United States can give us some useful perspectives in this respect, when considering the financial costs of green infrastructure in general.
- A study carried out in the United States of 479 green infrastructure projects found that 44 per cent of green infrastructure projects reduce total costs compared to the 25 per cent that increased the costs.
- A green infrastructure project in Philadelphia is due to cost $1.2 billion compared to over $6 billion for “grey” infrastructure over 25 years. It is estimated that: 250 people will be employed annually in green jobs; property values will increase by up to $390 million near parks and green areas over 45 years; reduction of up to 140 deaths caused excessive heat over 45 years; visits to parks and recreation sites will increase.
- It was estimated that a green infrastructure plan in New York City will cost $1.5 billion less than investments needed for grey infrastructure. It was also estimated that sustainability benefits over a 20-year period would range from $139–418 million. The plan estimates that “every fully vegetated acre of green infrastructure would provide total annual benefits of $8.522 in reduced energy demand, $166 in reduced CO2 emissions, $1,044 in improved air quality, and $4,725 in increased property value.”
Experience from many European countries also suggests that maintenance costs and responsibility for maintenance of Sustainable Drainage Systems (SuDS) is usually more challenging than the cost of implementing SuDS in new developments. Consequently, arrangements for maintenance of SuDS systems should be considered during the early stages of design, or there is a risk of turning a good SuDS implementation into a non-functional set of facilities.
