Evaluation of Wave Energy on the Willamette River

The trend of using larger boats for wake surfing in river systems has caused concern for dock stability, bank erosion, safety of other boaters, and natural resource conservation. This study evaluates the wave energy due to boat traffic in the Newberg Pool of the Willamette River using budget conscious equipment and involving community stakeholders. Low-cost motion activated game cameras were used to record videos of waves when boats passed. The video processing was completed using image analysis in the computational tool Matlab. For each image a high-contrast point of reference was used for the tracking, often tape on a dock piling. As the wave or dock moved, the reference point in the image was tracked in Matlab using the maximum or minimum grayscale pixel in a specific part of the image. This calculation allowed the research team to approximate the change in vertical direction in pixels. A computational analysis tool was used at 4 sites, 2 in wake surfing zones, 1 in a wake zone, and 1 in a no wake zone, to quantify wave height and period. A total of 8567 videos were collected from the four sites, and 1227 were analyzed. For the wake surfing zone, the average and maximum wave heights were 0.026 m and 0.149 m, respectively, and average and maximum wave energies were 0.905 W/m and 19.2 W/m, respectively. In the wake zone, the average and maximum wave heights were 0.031 m and 0.137 m, respectively, and average and maximum wave energies were 1.405 W/m and 5.74 W/m, respectively. The average wave energy was higher in the wake zone, however, the maximum wave height and the number of boat-caused waves recorded were higher (2984 in the wake surfing zone compared to 1117 in the wake zone) in the wake surfing zone. Cameras were attached to dock pilings which may have resulted in lower values due to the dampening of the dock. Wake surfing was also observed in wake zones, where it is not allowed. This study indicates that the large boats used for wake surfing create larger waves that can potentially cause damage to property along the river and natural resources. The processes and procedures used within this research would not have been possible without citizen involvement. The citizens partaking in the research allowed for their property to be used as a heavily monitored site or a self-monitored site. The self-monitored sites were a useful tool in collecting more data.