Author(s): Daniella Montali-Ashworth; Andrew Vowles; Gustavo De Almeida; Paul Kemp
Linked Author(s):
Keywords: No Keywords
Abstract: Gauging weirs often create barriers to fish movements, causing population decline because of habitat fragmentation and as such their retrofit is required so that fish can pass up-/down-stream. Gauging weir retrofit requires a reduction in water velocities to levels passable for fish, without affecting the gauging capabilities of the weir. Current fish pass designs are inadequate e. g. due to their high costs and impacts on gauging accuracy. The fish passage design discussed herein is low cost and has minimal effect on gauging. It is comprised of a staggered array of cylindrical clusters which create longer wakes and greater drag than if solid cylinders were used. The aim of this research is to determine whether this fish passage design can aid the upstream movement of non-salmonids over gauging weirs without affecting gauging. In an open channel flume, the hydraulic characteristics and fish passage efficiency is assessed and video recordings seek to understand how fish navigate the pass. A field evaluation aims to validate laboratory work by analysing fish passage efficiency in situ. Key findings highlight that fish can use the pass and the sinuous movements they exhibit when moving through the array from one low velocity zone to the next. Results also reveal that the overall drag coefficient of the array is greatest when array density and therefore wake overlap are least. The performance of the design within a river system under field conditions seems promising with passage efficiencies of 52% for chub (Leuciscus cephalus).
Year: 2018