FROM THREAT TO OPPORTUNITY – REVALUATING STORM WATER MANAGEMENT IN URBAN AREAS

Storm water has long been considered an obstacle with negative effects on movement and health in urban areas. But an increased focus on sustainability has led us to revaluate the role of storm water. The report “From threat to opportunity – revaluating storm water management in urban areas” investigates how sustainable storm water management can contribute to the creation of liveable cities.

There are various approaches to managing excess water originating from rain and snowfall. It traditionally includes drainage of water through infrastructure such as sewers, but increasingly sophisticated sustainable approaches with various “Blue-Green Infrastructure” measures are needed.  Without effective storm water management, it could cause flooding affecting the lives of the citizens living, working and moving through urban areas, and prevent the movement of goods and information. Sustainable storm water management combines conventional “hard” engineering with “soft” landscaping – to create Blue-Green infrastructure that uses storm water as an asset for green cities.

To ensure sustainable quality of life in liveable and attractive cities, we need to utilize many different ideas and perspectives on storm water management from storm water professionals as well as citizens. The Blue-Green Infrastructure (BGI) approach is of importance in securing a sustainable future and generating multiple benefits in the environmental, ecological, social and cultural spheres.

Sustainable storm water management schemes must be integrated design solutions involving a set of measures suited to specific local conditions. Such an integrated storm water system has not only to consider and manage storm water in present climate 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 utilizing various innovative technical solutions, including BGI.

There are three basic recommended stages to be taken when managing storm water in urbanized areas:

• The first step is based on the idea of keeping storm water where it 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 must be, in a third step, slowly drained through available or created waterways.

It is important to consider the design, construction and maintenance costs of BGI. Experience from many European countries suggests that maintenance costs and responsibility for maintenance of Sustainable Drainage System (SuDS) is usually more challenging than the cost of implementing SuDS in new developments. Responsibility for maintenance of SuDS needs to be clearly defined in legislation. However, financial costs of implementation can still present obstacles, particularly when robust legislation requiring SuDS is not in place. Various tools exist for comparing costs, potential benefits and cost savings over the lifetime of projects.

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.