Stormwater management in urban environment
Cities in the Baltic Sea Region are facing the common stormwater challenges: increased stormwater floods, degradation of natural resources and infrastructure caused by climate change, and densifying urban areas with the increased amount of impervious surfaces. The need for smart approaches to stormwater management is evident; but how to integrate them sustainably into the municipal practices?
The BSR WATER platform (Platform for Integrated Water Cooperation) focuses on a complex array of the water sector high-priority issues: sustainable stormwater management, nutrient recycling from wastewater, handling of hazardous substances and developing a cooperation model for interlinking water, energy and sludge. Bringing the focus to the stormwater, the platform shares experiences from two UBC Member Cities: Helsinki and Riga, that have been developing smart and integrated stormwater strategies and solutions, often in the broader transnational consortium.
City of Helsinki: Storm Water Management Program and a range of solutions
Helsinki is a fast growing city. With the estimated growth by 2050, the city will have to build new areas and face urban densification. Increased area of impermeable surfaces together with the challenges related to climate change, such as increased rainfall and rising sea level, call for strong emphasis on sustainable storm water management.
As part of the strategic work on climate change adaptation, the city developed an Integrated Storm Water Management Program in 2018. An integrated Storm Water Management Program means that the measures specified in the program are implemented and developed as an integral part of city planning, construction and various related processes (and mainly within the existing operational budgets). The Integrated Storm Water Management Program consists of six objectives and a priority order on how storm water management should be planned and how storm water should be treated and conveyed. Special emphasis is put on utilizing storm water as a resource for urban space, possibility to densify the city structure based on the city master plan, adaptation to climate change, promoting the new legislation, and cost monitoring.
The six objectives for storm water management stated in the Program are 1) to utilize storm water to increase the attractiveness of the environment, maintaining biodiversity and promoting a good condition of surface and groundwater 2) ensure regional and local drainage while taking the impacts of climate change into account 3) prevent and eliminate the disadvantages caused by storm water in changing conditions and densifying city structure 4) keep storm water flow rates under control and improve storm water quality 5) reduce storm water conveying into wastewater sewer 6) use cooperation and procedure models supporting systematic overall management of storm water, and secure sufficient competence and resources.
To improve the storm water quality, the city has implemented various solutions, a.o. Green Area Factor (GAF) planning tool to ensure sufficient green infrastructure when building new blocks in a dense urban environment.
City of Riga: Integrated stormwater management and cross-sectoral collaboration
Integrated Storm Water Management (ISWM) is a comprehensive approach to the challenge: instead of a narrow focus on a single problem, the ISWM undertakes a holistic stormwater management approach. ISWM studies the characteristics of specific sites and areas, understands the relevant impacts, and tailors a comprehensive array of tools to individual situations. Success requires the integration of the ISWM system into the urban development processes of the city at all levels, from urban planning to operation and maintenance.
Developed in the iWater project, the approach was taken up by the partner cities – Helsinki, Turku, Riga, Jelgava, Tartu, Gävle and Söderhamn, – the cities elaborated how to improve urban planning by integrating stormwater management into all urban planning stages as well as infrastructure construction, operation, and maintenance processes. Each partner city developed its own tailor-made solution: a city-specific stormwater management strategy, programme, or plan. The cities also established an institutional model for stormwater management based on a strong commitment of all involved stakeholders, coordinated cross-sectorial cooperation and balanced allocation of functions and responsibilities among municipal authorities and other local stakeholders, such as landowners, property developers, and other.
Cities are facing a problem of dispersed stormwater management responsibility. In turn, integrated stormwater management requires structured processes and people who know their responsibilities and work together towards common goals in accordance with a certain plan. In the iWater project, partner cities established local multi-sectorial consultative stormwater management groups that have an active and important role in supporting development of a city-specific integrated stormwater management strategy, programme or plan, and in localizing and adopting stormwater planning tools. By elaborating their integrated stormwater management strategies, the cities have taken a long-term commitment to continue their stormwater management work.