We have been involved with putting in quite a range of different fish passage solutions. We have installed Larinier passes, renovated old box passes and most recently, we have been involved in the building of a rock ramp on the River Almond at Livingston. There are many benefits of rock ramps over other types of fish pass, and it may become a method that we particularly recommend for future works.
The RiverLife project on the River Almond is in the process of installing fish passes on seven weirs, and currently weir number four is being addressed – the rock ramp being built at Livingston. This involves building a rocky ramp up to a weir across part or the whole width of the channel. The ramp is covered in boulders and rocks of different sizes, held in place by pins or concrete, and it appears as a sort of semi-natural part of the river bed (see photo). It creates a gently sloping river ramp up to the weir that fish can simply swim up and over.
There are many benefits of rock ramps over other fish pass options. Because it’s like a natural river bed, all species have a chance of being able to use it. Other fish passes focus mostly on salmon and trout, but the rock ramp allows all species the ability to move around. With a rock ramp, there would likely be a lot of different flow types and places to hide in amongst the rocks. Because our rock ramp is so big (the biggest in the UK), there are also special resting pools included where larger fish can lie safely waiting for better flows or to regain their energy.
Unlike technical fish passes, the rock ramp doesn’t get clogged up with debris and it requires no maintenance. It allows fish to pass during most flows (other fish passes only work within a window of flows) and it does not require fish to find the entrance to a narrow bottleneck in the river. A rock ramp can also actually serve to support old weirs that are in danger of collapsing and causing havoc with flooding or damage to infrastructure.
We are very excited to be getting the largest rock ramp in the UK installed on the River Almond and will be monitoring the benefits to biodiversity that it brings to the area. It is our hope that the same type of structure can be used to benefit rivers at other weir locations.