Foothills Fishery Facility at Colorado State University
Design and test a large flume to estimate slope and distance combinations that allow small-bodied fish passage through a rock ramp fishway.
Tyler Swarr and Dr. Chris Myrick, Colorado State University
The growing global need to improve the longitudinal connectivity of stream systems is often met by using fish passage structures (fishways). When designing fishways in the past, biologists and engineers focused primarily on strong swimming species such as salmonids. However, the majority of riverine species in the interior United States are not salmonids and may be excluded by fishways built using salmonid criteria due to lower swimming abilities and/or behavioral differences. Rock ramp fishways (sometimes referred to as nature-like fishways) are comprised of a sloped section of channel with roughness elements installed on the bed to provide velocity refuges and decrease water velocity for fishes as they ascend the fishway. This design is widely recognized as a good choice to allow passage of small- bodied fishes because they can be built without vertical drops, high velocity sections, and provide heterogeneous hydraulic conditions to accommodate a diversity of swimming behaviors.
This study was designed to improve the design of rock ramp fishways by identifying the ideal slope and length combinations for successful passage of small-bodied Great Plains fishes. A custom-made adjustable full-scale fishway was used to test fish passage success at slopes of 2 to 10% (Figure 1). This range of slopes, and associated water velocities, encompasses the range of slopes of existing or proposed fishways used along Colorado’s Front Range.
Multiple peer-reviewed publications have been submitted for review.