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Storm water solution

Storm water solutions as part of a green infrastructure methodology

Our growing and increasingly dense cities, with continually expanding impervious surfaces, put pressure on existing water drainage systems. Additionally, future climate change scenarios such as more intense rain events may further complicate the situation. This highlights the need for sustainable storm water management solutions.

The Sweco Urban Insight report “From threat to opportunity – revaluating storm water management in urban areas” details how storm water solutions may be used as a natural and multi-functional part of green infrastructure development.


European perspectives on storm water management – sponge city

The traditional approach for safe discharge of rainwater into a receiving waterbody during rainfall-runoff processes in urbanised areas – either in combined sewers and/or in storm water drainage systems – dramatically changed during the 20th century due to the expansion of urban areas.

In some cases, conventional engineering methods, such as sewers, have been complemented or replaced with alternatives using the green infrastructure approach. Examples include raingardens, green belts or grassed dry retention ponds. Also, modelling and master planning has become an important part of storm water management in cities.


What is green infrastructure?

The European Commission defines green infrastructure as:

A strategically planned network of high quality natural and semi-natural areas with other environmental features, which is designed and managed to deliver a wide range of ecosystem services and protect biodiversity in both rural and urban settings.

  • Green (or blue-green) infrastructure can be used as a way to achieve the aims of current directives and legislation. A network of green (land) and blue (water) spaces can improve environmental conditions and therefore citizens’ health and quality of life.

    The implementation procedure of some legislation has changed local (country) standards and led to guidance documents and policy advice for larger authorities, organisations and land managers. Legislation defines a framework of possible infrastructure changes and outlines the responsibilities of local institutions and other bodies.

    Current directives and legislation

    At the European level, there are various pieces of legislation relating to water management, and affecting storm water management to some degree, notably:

    • Water Framework Directive (WFD) requiring the protection and enhancement of waterbodies.
    • Floods Directive (2007)
    • Water Pollution by Discharges of Certain Dangerous Substances (2006)
    • Groundwater Directive (2006)
    • Habitats Directive (1992)
    • Urban Waste Water Directive (1991)
    • Bathing Water Directive (1976)


    Storm water solutions: current status in EU countries

    A brief overview of various European countries’ approaches to storm water solutions in the form of Sustainable Drainage System (SuDS), as perceived by selected experts involved in storm water management in those countries:

    • Sweden: SuDS is increasingly being installed in new developments, existing drainage is not being replaced, SuDS is an additional improvement.
    • Denmark: SuDS are enforced in any new urban development, regardless of whether it is private or public investment. Retrofitting of existing urban areas to include SuDS is also an important part of the paradigm shift towards more sustainable storm water management systems. It remains a challenge, however, due to space restrictions and conflicts of interest, such as removal of parking places to make room for blue-green areas.
    • Czech Republic: Although the principles of SuDS are known within the professional community, they have not been implemented in the legislation. Hence, there are only a few small projects where blue-green solutions have been implemented.
    • Netherlands: The approach to storm water management is increasingly focusing on SuDS, including blue-green solutions, stimulated by national government (Spatial Adaptation). There is discussion about investment and maintenance of green infrastructure solutions and how to persuade developers to implement SuDS.
    • UK: Surface water is managed by a complicated combination of public and private network of authorities. Despite an active online industry community (Susdrain website) and the implementation of many SuDS projects, including a few large-scale retrofit SuDS schemes, there are few incentives for developers. With a lack of clear funding and robust legislation there are practical difficulties moving things forward.


    Green infrastructure and city planning opportunities

The blue-green infrastructure approach to storm water management introduces new city planning opportunities, enabling a city landscape with more green areas. Designing storm water solutions in the form of SuDS is never a stand-alone procedure: it requires the full attention and co-operation of citizens and stakeholders in the urban planning process. There are many examples of potential benefits:

  • Transport infrastructure has to meet a multifunctional role. Raised roadways or embankments serve not only as a subgrade for various transport lines, they are also part of flood protection.
  • The street becomes a multifunctional conveyance system, combining traffic, a pedestrian zone, utilities conduit and waterway for retaining, storing and draining storm water.
  • The idea of minimizing environmental pollution, by city transport diversification for example, brings different traffic to the city. Heterogeneous ecological city transport, including active mobility in everyday life, is a great opportunity for building green streets, relaxing zones for pedestrians, parks and for implementation of protective storm water measures.
  • With proper consideration in the urban planning process, SuDS can also be used to help reduce heavy traffic by making foot and bike mobility more attractive, and thus alleviate vehicle traffic. For example, SuDS can be used to create more enjoyable, cleaner and safer streets.
  • Using green belts, pedestrian safety can be improved by separating vehicles from pedestrians, controlling movements of pedestrians, leading them to pedestrian crossings, and slowing traffic by narrowing road sections.

The above-mentioned facts emphasise once again the basic idea that careful planning on the level of storm water protection, optimal utilization of storm water and its overall integration into city infrastructure helps in building a better place to live.

For more information, conclusions, citations, and many additional examples, please refer to the full report: FROM THREAT TO OPPORTUNITY – REVALUATING STORM WATER MANAGEMENT IN URBAN AREAS

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