By Paul J. Sniadecki, MLSA Board Director
For the last few years, MLSA has contributed to the wake boat research being conducted by the Saint Anthony Falls Laboratory (SAFL) in the University of Minnesota. In previous newsletters we have reported on SAFL’s Phase 1 studies that measured the impact of diverging waves. Such waves occur when watercraft purposely generate large and high energy waves for surfing and jumping. SAFL’s findings documented that such diverging waves do not significantly decrease in size/intensity until they are 500-1000 feet away from the hull.
SAFL’s Phase 1 research on boat-generated waves was published in 2020. The interest in that report was immense and provided the momentum needed to conduct a Phase 2 study on boat-generated propeller wash and potential impact on the lake bottom environment. The SAFL team completed Phase 2 fieldwork in the fall of 2022, with the intent to publish a peer-reviewed report in the fall of 2023. However, they observed interesting but unanticipated phenomena during data analysis and realized that to publish a thorough Phase 2 report, they needed more data. What the research discovered is that such watercraft also generate transverse waves off the stern of the boat and travel in the same direction as the boat.
Transverse waves are produced when boats travel below the speed at which the boat can plane. The fall 2022 data indicated there is a measurable effect of both propeller wash and transverse waves in the
water column and on the lake bottom. SAFL then initiated Phase 3 with funding secured from the Minnesota Environment and Natural Resources Trust Fund (ENRTF) as recommended by the Legislative Citizen Commission on Minnesota Resources (LCCMR). The additional fieldwork was completed in the fall of 2023. During the winter of 2023-2024, SAFL will be working to complete data analysis and publish findings from the combined propeller wash research effort. They are working on answers to the following questions:
- For different boat sizes and usage scenarios, how deep does the propeller wash penetrate the water column?
- What are the associated water velocities?
- At what depth does propeller wash begin to interact with the lake bottom?
- What happens when it does (e.g., sediment suspension, changes to water quality, aquatic vegetation)?
Clearly, good science takes time. While we all want actionable findings now, we have to wait
a little longer. Good science is a good thing. You can find out more about this newest project update and other messages from the research team on the project website. (Note: MLSA’s financial contributions to this research would not be possible without the support of our dues paying members. We thank you for your continued membership!)