Modeling Fish Passage Through Nature-Like Rapids Using Civil3D and HEC-RAS in the Context of Dam Removal
Samuel H. Prentice, PE
GEI Consultants, Inc.
Marquette, Michigan
Authors: (Aadland, Taillacq, & Prentice)
Fish Passage Design input provided by Dr. Luther Aadland. Hydraulic Modeling completed by Andrea Taillacq of Tailwater Limited. Project design and presentation by Samuel Prentice
Traditional fish passage structures have been created with little regard for the natural energy dissipation characteristics of rivers and streams. Using baffles and compartments is ineffective in passing fish, especially warmwater species that are not as strong swimmers and jumpers as coldwater species. Recently, biologists and engineers have started working together to design fish passage structures that better emulate natural stream processes. Dr. Luther Aadland has used this approach on many different projects throughout the midwest and across the country. His input into the design process has created nature-like fishways that facilitate passage of the full spectrum of native species.
While design of these structures and passage of fish can be verified in the field, it can be challenging to model using traditional three-dimensional grading software like AutoCAD Civil3D and two-dimensional hydraulic modeling programs like hec-ras. The Civil3D model results can be used to inform contractor quantities and cost estimating, while the hydraulic modeling can be used as a powerful visual tool with regulators, clients, and stakeholders using water depths, velocities, shear stress, and Froude number results as surrogates for fish passage success.
This presentation will highlight the modeling tools used in both Civil3D and hec-ras for two active projects in Michigan where dam removal is being considered and impoundment elevations must stay at or near current elevations for multiple technical and community reasons. In both instances, an engineered structure spanning the entire river width consisting of rock and boulders was designed to emulate a natural rapids and maximize fish passage success, create beneficial aquatic habitat within the structure itself, remove dams that pose a public safety risk, and maintain impoundment elevations for continued use and minimal ecological disturbance.
About Samuel H. Prentice, PE
Samuel Prentice is a licensed civil engineer working as part of a collaborative team specializing in ecological and environmental consulting. The team works together with several clients to provide data collection, analysis, report, and design services. His responsibilities include data collection, hydraulic modeling, sediment transport analysis, design, and construction oversight for stream restoration and fluvial geomorphology projects. Over the last few years, Mr. Prentice has worked directly with Dr. Luther Aadland to design fish passable rapids in Michigan at two project locations. Mr. Prentice has also completed all four levels of Dr. Dave Rosgen’s Natural Channel Design courses.
