Characteristics of recreational boat wakes

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The applicability of using a boat’s size and speed to predict remotely the energy in its wake was studied. A portion of the Georgiana slough, a tributary of the Sacramento River, was instrumented with a data logger, camera, and KPSI 720t pressure transducer to record boat passages and the resulting wake. The camera was set to record only when triggered by a motion sensor and the data logger to save data only during daylight hours. The instruments were left in place for roughly the month of September 2009. The data gathered were then grouped into wake categories based on size, speed, and boat type. Distance from shore for each boat track creating a wake was assumed to be the same for all boats in the relatively narrow channel. A low statistically significant correlation (linear regression) was found between boat speed, size and type with measures of shoreline wake heights. Turned out to not correlate well. This surprising result may have been caused by several factors to be discussed but mainly due to boat length not actually capturing boat displacement which when combined with speed creates disturbance we see in the form of a boat wake. Using a double reciprocal regression model 〖boat size〗^3 was found to have the strongest correlation to index wave energy with an r^2 value of 87, and a p < 0.0001. Boat size was raised to the third power as a surrogate measurement of boat length, width, and hull depth to better capture a metric more closely associated with disturbance force. These results suggest that a boat’s size, which can be obtained remotely from cameras, can be used to help predict the energy content of the wake it can produce. This could be used to monitor remotely areas to help assess possible erosion impacts due to boat wakes and possibly help to establish no wake zones for sensitive water bodies.

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