Boat-Generated Wave and Turbidity Measurements: Connecticut River

Abstract

Waves generated by high-speed recreational boats can play a significant role in bank erosion and failure along riverbanks. Frequent passes of these boats in confined channels increase suspended-sediment concentration and turbidity at relatively shallow water depths, and increase the erosion rate by wave breaking and long-shore currents. In the current study, boat-generated waves and turbidity were measured in the Connecticut River along a reach between Vernon Dam, Vernon, VT and French King Bridge, Miller Falls, MA. Two-meter-long self-powered, self-logging wave staffs were used to measure the water level and waves at three sites. Based on these uninterrupted measurements, boat-generated wave-characteristics were obtained for a period of four months between May 2015 and September 2015. As part of this study, turbidity and wave measurements at these three sites were carried out during a series of in situ experiments with a 5.7 m long tri-hull motorboat. The experiments included a total of 36 controlled passes parallel to the shoreline at speeds ranging from 8 km/h up to 55 km/h. Boat speed and path was measured with a global positioning system (GPS) logger and the turbidity level near the bank was measured using two optical backscatter sensors. Relations between the wave height, wave period and turbidity level were investigated. This paper presents the results of these additional measurements and discusses relations between turbidity levels and boat-generated waves.