A Field Study of Recreational Powerboat Hydrodynamics and their Impacts on the Water Column and Lakebed

Abstract

The increase in powerboat popularity, along with increasing boat size, horsepower, and newer wake-enhancing technologies, has led to increasing concerns for the health of these aquatic environments. More specifically, wakeboats and the mode in which they are operated during wakesurfing is a topic of intense public interest. The motivation of this field-based research study was the need to better understand the environmental impacts within the water column and at the lakebed as different types of recreational powerboats traverse under their typical modes of operation. The objectives of the study were to: 1) clarify and define the various hydrodynamic phenomena that are created by a recreational powerboat in motion, and how these phenomena vary with water depth and mode of operation, 2) investigate the depth of penetration and duration of emission gases (e.g., engine exhaust bubbles), 3) investigate the water column velocities and depth of penetration of the bow, stern, and transverse waves and their potential to resuspend lakebed sediment, 4) Investigate the propeller wash velocity and depth of penetration, and the potential to resuspend lakebed sediment, 5) investigate the effects of repeated boat passage on thermal stratification and mixing in the water column, 6) capture underwater and aerial video of the hydrodynamic phenomena and any subsequent impacts (e.g., sediment resuspension). This study generated a wealth of data that we used to developed recommendations on the minimum operational depth that recreational powerboats, under typical modes of operation, should maintain to minimize impacts to the lakebed.