It is possible to observe the progress of works concerning the “Longitudinal connectivity restoration: Action C.4” thanks to the beautiful pictures taken by Marco Tessaro from the drone. The first picture shows the rock ramp at the Migiandone Bridge (Toce01 – Weir on River Toce at Migiandone Bridge) and the second shows the working site of the pool fish passage type at the Lake Tana dam (Toce04 – diversion dam of Lake Tana – Enel).
The two works have the same goal to restore the longitudinal connectivity of the River Toce, but from an engineering point of view they have different features. A rock ramp has a natural like aspect, the drop created by the discontinuity is passed thanks to the positioning of the rocks like a “ladder” and the morphology is similar to a stream. A pool fish passage type is made by a concrete channel characterized by a fixed slope, where the drop between upstream and downstream is divided by a specific number of pools delimited with cross septa. This septa, that dissipate the energy of the water, can be compared to the stairs of a ladder and have a fissure to allow the transit of the fish.