ABSTRACT
The observation of sediment fluxes in rivers is required for management of navigable waters, reservoir maintenance, understanding sediment budgets that can impact ecological habitat integrity and prediction of the morphodynamics of the river and its delta. We report on a program of multi-frequency acoustic sediment flux measurements in the Fraser River at Mission, BC, where three side-looking Acoustic Doppler Current Profilers (ADCP) are installed. The ADCPs have frequencies of 300,600 , and https://www.w3.org/1998/Math/MathML"> 1200 k H z https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780429069246/b59e18fc-9e1d-4389-b000-a1069c1cd27e/content/eq12655.tif" xmlns:xlink="https://www.w3.org/1999/xlink"/> and range from 25 to 60 m into the 550 m wide channel. Bottle sampling is underway to collect a series of vertical profiles of point-integrated and depth-integrated samples to calculate the grain-size specific sediment flux in the river. We also collect a series of point-integrated sediment samples in the acoustic beam for acoustic calibration purposes. These samples are analyzed for both mass concentration and sediment size distribution. Each ADCP records data continuously at six minute intervals, through both low flow periods and the annual freshet, allowing for an estimate of the yearly total and sand sediment flux. Eight sampling campaigns were undertaken from June to September of 2012 to provide calibration points for the acoustic analysis and 8 campaigns were undertaken in 2013 to evaluate the calibrations. The sonar equations and data from the 2012 hydrologic year have been used to model suspended sediment fluxes. Results show coefficients of determination for modeled versus observed total flux for all three frequencies as 0.96,0.93, and 0.94 for the 300,600 , and https://www.w3.org/1998/Math/MathML"> 1200 k H z https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780429069246/b59e18fc-9e1d-4389-b000-a1069c1cd27e/content/eq12656.tif" xmlns:xlink="https://www.w3.org/1999/xlink"/> ADCPs, respectively. Sand flux had lower coefficients of determination of 0.71 and 0.82 for the 600 and https://www.w3.org/1998/Math/MathML"> 1200 k H z A D C P s https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780429069246/b59e18fc-9e1d-4389-b000-a1069c1cd27e/content/eq12657.tif" xmlns:xlink="https://www.w3.org/1999/xlink"/> . The https://www.w3.org/1998/Math/MathML"> 300 k H z A D C P https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780429069246/b59e18fc-9e1d-4389-b000-a1069c1cd27e/content/eq12658.tif" xmlns:xlink="https://www.w3.org/1999/xlink"/> had poor correlation with sand fluxes due to the low frequency but has proven the most effective instrument for velocity-index discharge measurements. The results suggest that reliable sediment flux estimates can be obtained using ADCPs.
