Helsinki study recommends keeping Vanhankaupunginkoski dam

A new Helsinki city study recommends keeping the dam at the Vanhankaupunginkoski rapids and restoring the eastern branch instead, a cheaper option that would improve fish passage and ecological diversity, Yle reports.

The study compared the effects of removing or retaining the dam. It concludes that restoring the eastern branch while keeping the dam on the western branch would be the most suitable solution.

Removing the dam could lower water levels and leave parts of the channel dry at times. It would also require extensive further planning and permit procedures. Further planning is estimated to cost 600,000 to 900,000 euros, while removal would cost an estimated 2 million to 3 million euros.

The eastern-branch restoration is estimated to cost about 650,000 euros. The plans are complete and have received a permit under the Water Act. The work would make the fish passage less steep, add resting areas and natural stones to the channel, and create a gravel bed for spawning near the head of the rapids.

The increased flow would guide fish into the eastern branch more effectively and improve the chances of several species reaching the Vantaa River. The restoration is also expected to improve recreational use and safety.

Debate and studies on options for improving the rapids have continued for more than a decade. In June 2022, Helsinki City Council decided to begin planning the partial or complete removal of the dam.

The surroundings of the Vanhankaupunginkoski rapids are among Helsinki’s historically layered areas. A village stood there in the Middle Ages, before Helsinki and the royal manor were founded in 1550. The area is also significant as the city’s birthplace and as the location of a waterworks that operated from 1876 to 1971.