Wave height from planing and semi-planing small boats

Abstract

The increasing number of small boats has raised concerns about their effects on the environment, particularly their waves. Bank erosion is one of the foremost concerns of boat waves but disruption of habitat, resuspension of bottom sediments, and damage to aquatic plants are other areas of concern. A large programme of field measurement of boat waves was conducted on Johnson Lake in Alaska to evaluate boats typically used on the Kenai River. The boat wave study compared wave characteristics of four boats under a variety of loadings, speeds, distances and motor powers. Over 400 tests were run on Johnson Lake with each test providing wave measurement at four locations. Two measures of waves and two types of tests were used in the study. MAX-POW was the wave height at the maximum power of the motor. MAXWAV was the maximum wave height produced by the boat which required runs at a range of speeds to determine the MAXWAV. While the MAXWAV data herein have considerable scatter in magnitude, the conditions at which MAXWAVoccurs are consistent from boat to boat. To prevent generation of maximum wave heights, small boats should operate as far as possible either above or below length Froude number of 0.6, displacement Froude number of 1.3, or beam Froude number of 1.0. A general boat wave height equation was developed for the four boats based on boat speed, volume displaced by the boat and distance from the boat, and are applicable to semi-planing and planing boats based on MAXPOW and MAXWAV data. The predictive equation for V-hull boats was compared to independent data not used in the development and was found to be in agreement with the data.

Human impacts to mountain streams

“…7 Wohl (2001), Törnlund and Östlund (2002). 8 Scott (1982), Wohl (2001), Bauer et al (2002), Paul et al (2003), Maynord (2005). 9 Graf (1978), Thompson and Rahel (1998), Goodsell and Kats (1999), Adams et al (2001), Peterson et al (2004).…”

Little boats and big concerns? Seeking a balance between ecotourism and motorboat use in Tortuguero, Costa Rica.

“…This result differs from much of the literature, which tends to emphasize the environmental impacts of motorboat related erosion (e.g. Dorava, 2001;Maynord, 2005;Parnell, 2001), and not the social and economic implications of shoreline property loss due to erosion. While literature on property loss via erosion exists about landslides, beach front properties and wave-caused erosion (e.g.…”

“…were to be introduced as an attempt to minimize boat-caused waves, this could help to reduce shoreline erosion Beachler & Hill, 2003;Dorava & Moore, 1997;Maynord, 2005), and might also serve to reduce related local concerns and worries. This will be discussed in greater detail in Chapter 5.…”

“…Many erosion-related motorboat studies focus on experimental boat wake-induced erosion impacts on wildlife or the environment along banks uninhabited by humans (e.g. Bauer, et al, 2002;Dorava, 2001;Maynord, 2005). In addition, many such studies use technologies that are expensive and unavailable to most of the developing world (Altbach, 2004).…”

“…Potential erosion increases with speeds from idle (0-3 mph or 0-5 km/hour), to a slow speed (5-7 mph or 8-11 km/hour), and then to a medium or plowing speed20 (10-20 mph or 16-32 km/hour), but this is in fact where the maximum displacement of water occurs, before all higher speeds. In other words, it is at this medium speed where the greatest waves are produced, causing the greatest potential for shoreline erosion Maynord, 2005). The speed-erosion equation or relationship changes from this point onwards, as speed continues to increase the potential of shoreline erosion decreases.…”