Longinoja was once a naturally meandering stream before it was straightened to form a straight ditch in order to drain rainwater as fast as possible from residential neighbourhoods.

The flow of water in straight ditches varies a lot, causing erosion along the banks.

This section of the stream leading up to the Kehä I ring road has been restored as part of a joint project between several authorities.

During the restoration project, the natural bends were returned to the stream. Large rocks, gravel beds and deep pits were also added for the trout.

Thanks to the restoration, hundreds of trout have successfully spawned in the stream, producing breathtaking numbers of smolt!

Straight ditch:

• Flow varies
• Banks collapse
• Murky water
• Fish eggs suffocate

Before and after