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

我们申请资助一个流线型激光原位沉积物透射仪（list - sl），用于观测大型沙层河流中的悬浮沉积物。listst - sl同时测量水流流速、悬沙浓度和水柱中某一点的粒度分布，这三者结合起来可以在大范围的泥沙粒径范围内测量悬沙通量。申请人合作研究地球表面上的沙层河流的动态，这在很大程度上是由悬浮沉积物的运输控制的，以响应每年的洪水。我们目前的研究重点是了解悬浮沉积物在大型河流中的运动，作为冲刷荷载（持续悬浮的泥沙和粘土）和床质荷载（间歇悬浮的沙子）。这项工作的大部分是在弗雷泽河下游进行的，我们的发现对港口管理具有重要的实际意义。这项工作需要坚固的设备，能够承受通常超过3米/秒的流动应力。我们目前的仪器不是流线型的，因此部署费用昂贵（大型船只仅500美元/天），精确定位是不可能的，采样不是等速的（测量结果在计算沉积物通量时不可靠）。list - sl将为我们的研究小组提供流向速度、悬浮沉积物浓度和强深流粒径的等速测量，这是我们研究项目的基础。它还将使我们能够与加拿大水务局合作，校准使用声学多普勒电流剖面仪对悬浮沉积物进行常规传感的全新方法。

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.