Integrated Storm Water Management


Cities in the Baltic Sea Region are facing common challenges of increasing storm water floods and degradation of natural resources and infrastructure caused by climate change and densified urban areas.

Urban development removes the vegetation that intercepts, slows and returns rainfall to the air through evaporation and transpiration. These changes not only increase storm water runoff, but also accelerate the rate at which runoff flows across the land. Drainage systems such as gutters, storm sewers and lined channels designed to quickly carry runoff to rivers and streams, further exacerbated this effect.

The trend in land development towards densifying urban areas and increasing impervious surfaces also reduce the amount of water that infiltrates into the soil and groundwater, thus reducing the amount of water that recharges aquifers and feeds stream flow during periods of dry weather.

Land development and urbanization also affect storm water quality by increasing both the concentration and types of pollutants carried by runoff, while the loss of the original topsoil and vegetation removes a valuable filtering mechanism for storm water runoff.

Finally, urban development within a watershed has a direct impact on downstream waters causing changes in the stream flow and geometry, degradation of aquatic habitat and, water quality impacts. Urbanization changes watersheds in a multitude of ways, and generic solutions cannot manage all the impacts. Besides, cities in Baltic Sea Region are facing a problem of dispersed storm water management responsibility.


How land is initially developed has tremendous bearing on the prospective quality of urban streams. Traditional approaches alone fall short of maintaining the integrity of water resources. Success requires going beyond a narrow focus on a single problem to undertaking a comprehensive water resource protection strategy: recognizing the characteristics of specific water resources, understanding the relevant impacts, and tailoring a comprehensive array of tools to individual situations.

iWater project will develop a comprehensive storm water management approach and integrate it into the urban development processes of each city at all levels. This ambitious project will also involve all stakeholders in the process offering them the opportunity to cooperate in the development of the Integrated Storm Water Management (ISWM) and Green Area Factor Tools (GAF).

The objective is also to develop guidelines for this Integrated Storm Water Management system and, by following the guidelines, the partner cities will develop and adopt their own Integrated Storm Water Management programme or plan. The guidelines will also include hands on instructions for carrtying out a peer review process between local or regional authorities, and the evaluation criteria for the peer review.

iWater will also develop content for the training of other Baltic Sea Region cities and regions to use the Integrated Storm Water Management system.


By the end of the iWater project each of the 7 partner cities will have adopted its own ISWM programme or plan. Approximately 35 Baltic Sea Region cities will be trained using the ISWM guidelines and training material.

There will also be an increased awareness of the benefits of using a comprehensive storm water management approach, integrating the storm water management into the land development processes, and using multifunctional green infrastructures that include storm water management solutions.