Project Overview
In Autumn 2020 Cain Bio-Engineering, alongside Wessex Rivers Trust (WRT), completed the construction of a fish pass on the Bourne Rivulet (a tributary of the river Test) in Hampshire. The disused sawmill at this location posed a complete barrier to fish passage, impeding connection between spawning and juvenile habitats upstream, and an abundance of adult habitat downstream.
Cain Bio-Engineering installed a rock ramp style fish pass to facilitate fish passage up and downstream. The weirs within the existing channel were ‘notched’ and the bed level raised with rock and gravel, creating a sinuous ‘nature like’ rock ramp with streaming flows. A further weir, approximately 50m downstream, was also notched to enhance attracting flows for fish to the fish pass channel.
Before
Aerial view of the existing channel containing a series of concrete weirs 
Downstream view of the existing channel 
Upstream view of the existing channel 
Upstream view of the existing channel after de-watering
During
Upstream view of the de-watered channel with notched weirs 
In-channel installation of rock for the rock ramp 
Installed rock ramp prior to re-wetting of the channel
After
Aerial view of the completed rock ramp 
Upstream view of the alternating pool & chute sequence of the rock ramp 
Downstream view of the completed rock ramp & offtake
