Water Resources Engineer GEI Consultants Marquette, MI
Abstract Description: In 2024, GEI modified an existing dam through design and construction of a fish-passable rock rapids. This constructed rapids is 650-feet in length and drops nearly 14 feet, allowing the owner to maintain a similar minimum water surface to the former dam while also meeting regulatory fish passage requirements. Volitional fish passage for cold and warmwater species has been demonstrated on similar nature-like fishways throughout the Midwest using a series of boulder, gaps, and resting pools that emulate natural river processes. This is the first design of its kind to be constructed in Michigan, with notable differences to other previously constructed rapids in Michigan with varied fish passage success.
This design is a viable alternative for dam owners and regulators where fish passage is desired, a minimum water surface elevation is required, and no additional water control is necessary.
This presentation will share design criteria related to flood control and volitional fish passage, interpreting two-dimensional modeling results related to rock sizing and fish passage, and lessons learned during construction.
Learning Objectives:
Describe the advantages of rock rapids for fish passage at dams in relation to other traditional fish passage approaches (dam removal, bypass channel, fish ladder, trap and transfer, etc.).
Describe development of design constraints based on selection of desirable species passage (include volitional/non-volitional considerations).
Share lessons learned from construction presentation related to summer low flows, rock material sizing, and construction sequence.
