Protecting Baltic Sea from untreated wastewater spillages during flood events in urban areas

New storm water management solutions must be found due to the increasing intense waterfalls and storms appearing in the Baltic Sea Region. Urban areas need to be better prepared for floods by improving their planning as well as their self-adaptive drainage operations as the current ones are not sufficient in the changing climate situation. During the BSR NOAH project different stormwater management systems have been installed and tested in several countries in the Baltic Sea region.

Solution to which problem

Effective control of stormwaters in urban areas is one of the biggest environmental challenges in the Baltic Sea region due to rainfalls and storms caused by climate change. As the urban drainage systems are not adapted to handle the increasing amount of stormwater, floods have become more common in densely populated areas. Floods increase the risks of flushing untreated wastewater from urban drainage systems into nature. This is harmful to people and nature due to the excessive amount of nutrients, hazardous substances, and pathogenic microbes in wastewater.

Technical conditions

The BSR NOAH pilot sites are urban areas that are situated next to a natural water body (sea, river, channel) and connected directly to the Baltic Sea. In the sites, extra flow rates in the urban drainage system poses a risk of wastewater spillages during extreme weather events. The sites have an existing urban drainage system built but are in the need of improvements. The aim of the pilot activities was to test and implement a set of solutions which as the NOAH concept are scalable to any urban area in the Baltic Sea region.


In the project pilot sites, different stormwater management systems were installed and tested. The pilot sites, located in Estonia, Poland, Latvia, Sweden, and Finland were equipped depending on their specific needs. Either automated hydrological stations or smart weirwall systems were installed.

Further information on the locations and installations at

In addition to installations, a new planning tool EWL, extreme weather layer, was developed and introduced to specialists in urban planning to help them depict the flood risk levels of certain urban areas.


Depending on the pilot area, the installations managed to improve the control of stormwaters and reduce the risk of wastewater spillages. Future planning of urban areas needs to take stormwater control into account more widely.

Considering the piloting process, paying attention to local policies, budget and timeframe of the installations is important. Additionally, procurement procedures may vary between municipalities.

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