Wake Boats and Wave Physics

…in Vermont Lakes. By Phil Logsdon of Sunset Lake.

As a University Physics professor, I am pleased when science is applied to decision-making. Those studying appropriate distance from shorelines for wakesports have heard strong biology and ecology science arguments for a 1,000-foot restriction. That science is extremely compelling.  Because physics predicts significant adverse consequences of any limits set below 1,000 feet, I implore the Agency of Natural Resources (ANR) Secretary Julie Moore to factor wave dynamics science, explained below, into the ANR’s recommendations.

  • The Law of Conservation of Energy. This law states that energy can neither be created nor destroyed.  When applied to wave physics, this means that total wave energy remains unchanged. Wave energy is a function of wave speed, length, and height. When any of these components changes, the remaining components must adjust to the changes to maintain the energy level contained within the wave.
  • Nature of Wake Energy in Vermont. Waves and wave energy behave differently on Vermont’s glacially scooped out lakes than on lakes with gradually upward-sloping shorelines, such as the one included in the 2015 industry-sponsored Goudey study in Florida.  Wave energy drives a process called shoaling, as the bottom portions of waves encounter a rising lake floor. As this happens, the wave slows and the wavelength shortens, forcing the wave to maintain its energy level by increasing its height. Waves on Vermont lakes more often encounter steeply-rising floors — sometimes cliff-like. This causes waves to react more forcefully than they would on gradually sloping lake beds, and the waves produced are bigger and more powerful.  Extreme examples of this process are tsunamis.
  • Effect of Wake Boats on Wave Energy. Wake boats exacerbate the shoaling process by injecting high-speed jets of water deep into lakes.  Some of this wave energy rises immediately to create the “surf” plume behind the boat.  Other energy becomes longitudinal deep-water waves and transverse air-water interface waves that radiate toward the shore. Wave energy travels much faster and more powerfully longitudinally through incompressible deep water than through air or air-water surfaces.  This is why submarines fear depth-charges. Deep water energy must forcefully move upward when meeting a steep lakebed rise, the type encountered in many Vermont lakes.  Upon encountering sharply rising Vermont lake beds, radiating wake boat waves become tall transverse waves very quickly.  These high, powerful waves wildly toss about swimmers, kayaks, canoes, paddle boards, and even boats and docks – as has been extensively documented in oral and written public testimony presented to the ANR.  After deep water waves blast upward — as wave energy physics requires — they bounce off arcing shoreline coves to recombine dramatically near the cove-center nesting areas of loons and other wondrous aquatic life.  Cove centers are also where young and old humans enjoy swimming and tranquil paddling.
  • Impact of Multiple Wake Boats on Wave Energy. The above concerns are greatly exacerbated if more than one wake boat is operating at a time.  Waves from multiple wake boats operating simultaneously can combine to create enormous waves. Moreover, the wave energy generated by wake-boats grows each year as new boat designs increase wake boat size, weight, and power.  Future prospects for multiple, simultaneously-operating wake boats underscores the need for the ANR to apply the precautionary principle as they develop their strong 1,000-ft minimum distance from shore rule for wake sports.

The science of wave dynamics physics and our unique Vermont lakes speaks compellingly in support of restricting wake boat use to a minimum 1,000-foot distance from our near-shore precious lives, ecosystems, and activities.

  • Philip Logsdon, Physics Professor delighting in the Lake Sunset ecosystem with family and friends for 50 years.    466 Hyatt Camp Road, Benson VT       Phil.logsdon@gmail.com

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