The IdroLIFE Action – Action C4

Action C.4 of this project is responsible for the restoration of river continuity for fish in the stretch of Toce River that flows from its mouth in Lake Maggiore to 45 km upstream and in the Torrente San Bernardino. There are 4 impassable barriers on the Toce and one on the San Bernardino: these obstacles prevent the free migration to fish and can be mitigated by building passages for fish, real “water stairways” built for them.

At the Verbania weir, 1,000 m upstream from the mouth, there is the only impassable barrage of the San Bernardino stream. In order to defragment it, a stone ramp was built and was then malfunctioning.

The stone ramps are anthropogenic structures that look extremely natural that face the jump generated by discontinuity by means of a ramp of boulders arranged “on a scale”, with a morphology quite similar to that of a stream, but with an “entry” of valley and a clearly identifiable and walkable “exit” at the top. If the tilt is excessive or the harnesses are poorly structured, the water flows too fast and turbulent, and the fish fail to get past the structure.

As part of this project, the modification of the ramp has now been completed and the free travel of its 8.5 km in length is guaranteed: studies of marking and recapture of trout allow to verify the operation of the work.