Streamlined isokinetic sediment sensor for studies of suspended sediment flux in large rivers

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We request funding for a streamlined laser in-situ sediment transmissometer (LISST-SL) for observations of suspended sediment in large, sand-bedded rivers. The LISST-SL simultaneously measures streamwise fluid velocity, suspended sediment concentration and grain size distribution at a point in the water column, which combine to yield in-situ measurements of suspended sediment flux for a large range of sediment sizes. The applicants collaborate to examine the dynamics of sand-bedded rivers across Earth's surface, which is largely controlled by the transport of suspended sediment in response to annual flood flows. Our current research is focused on understanding the movement of suspended sediment through large rivers as wash load (silt and clay in persistent suspension) and bed-material load (sand in intermittent suspension). Most of this work is conducted in the lower Fraser River, where our findings have important practical implications for port management. This work requires robust equipment capable of withstanding stresses in flows that routinely exceed 3 m/s. Our current instruments are not streamlined so deployment is expensive ($500/day alone for a large vessel), precise positioning is impossible, and sampling is not isokinetic (measurements are not reliable for calculating sediment flux). The LISST-SL will provide our research group with the isokinetic measurements of streamwise velocity, suspended sediment concentration and particle size in strong and deep flows that are fundamental to our research programs. It will also enable us to collaborate with the Water Survey of Canada on the calibration of radically new methods for routine sensing of suspended sediment using acoustic Doppler current profilers.