Lahti’s stormwater strategies aim at reducing the negative impacts caused by stormwater discharges. Centralised storm water sewer systems reduce environmental nutrient loads efficiently. Lahti’s Storm Water Management Plan aims to improve cooperation and knowledge of storm water issues and develop new best practices for storm water management. The plan emphasises the importance of ecological storm water management in newly built areas. Approximately 20 retention ponds and wetlands have been constructed in Lahti during recent years. After management, storm water is directed into bodies of water, with the Porvoonjoki River the biggest reserve. If necessary, sand filters are used for the treatment process. Lahti’s Storm Water Management Plan aims to: · Improve storm water management (i.e. avoid floods and ensure that building foundations remain dry) · ensure groundwater quality and –recharging · improve storm water quality and reduce negative impacts on the receiving bodies of water · add biodiversity and increase its value · improve co-operation and knowledge of storm water issues · develop new best practices for the management of storm waters Storm water policy emphasises achieving gradual but continuous improvements in storm water management capacity using a combination of proven management practices and modern sustainable drainage systems whenever possible. RAINMAN project Starting in 2018, the RAINMAN project will respond to surface and groundwater challenges arising from urban growth, climate change and storm water floods. Lahti rarely suffers from urban flooding, but sometimes the heavy rain management expertise gained and flood route planning carried out come in handy.