What is the cost of installing a fish ladder on a wier?
The costs depend on the channel slope, the height of the weir, width of the stream (if you want to span the channel), water velocity parameters, height of the steps, and the materials you want to use. The cheapest design is probably a swimmable boulder cascade, which is nothing more than several layers of boulders irregularly placed below the weir to create multiple paths there the fish can work their way through the rocks. In the bottom layers, sands, clays and pebbles are packed in between the boulders to force the water to flow over the boulder instead of through them. With weirs, the most common approach is to replace a single weir with several smaller weirs that have a lower jump height and suitable water depths and velocities over a wide range of flows. This is very easy and somewhat inexpensive to do with boulders and an excavator. The most expensive part of this type of approach is the engineering and surveying to make sure the elevations and distances are designed correctly. I
