Flow measurements by acoustic scintillation drift in the Fraser River estuary

Abstract

A prototype of an operational acoustic scintillation flowmeter has been installed and operated periodically in the estuary of the Fraser River in British Columbia since 1990. The instrument transmits 200 kHz acoustic signals along two parallel paths across the river and from their fluctuations measures the spatially-averaged flow normal to the acoustic paths, in real time. A nearly continuous record of seven months duration was obtained in 1991, before river traffic damaged the installation. A comparison with an acoustic Doppler current profiler operated from a launch showed agreement for flow speeds up to 1.4 m/s. The record from the scintillation flowmeter also revealed the occasional presence of fluctuations in the spatially-avenged flow of 20 to 25 minutes period and 2.5 cm/s amplitude. As well as continuous flow speed and transport estimates, there is also the possibility of detecting changes in the concentration of suspended sediments, the turbulent refractive index and other properties of the flow.<>