Video observations of bed form morphodynamics in a meander bend
Video observations of bed form morphodynamics in a meander bend
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DOI：
10.1002/2014wr016321
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发表时间：
2015-09
影响因子：
5.4
通讯作者：
M. Palmsten;J. Kozarek;J. Calantoni
中科院分区：
文献类型：
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作者：
M. Palmsten;J. Kozarek;J. Calantoni
介绍了一种新的光学遥感技术，用于从倾斜相机视图估计水深。同时对水面和河床进行成像，以创建水面速度和河床高程的随时间变化的地图，这些地图可用于以高空间和时间分辨率验证数值模型。该技术被应用在明尼苏达大学圣安东尼福尔斯实验室室外溪流实验室的一个桑迪曲流弯曲。床的光学估计和原位观测之间的均方根差在0.01和0.03米之间。平均床形波长为0.73 m，平均波峰高度为0.07 m，但都随曲流弯曲周围的距离而变化。底形分类随下游距离的不同而不同，底形的弯曲度随局部曲率半径的不同而不同。床形粗糙度缩放类似于其他自然河流环境，虽然波长和高度的大小和变异性大于预测的经验公式的直线河段。床型平移速率在1到5 mm s-1之间变化。从粒子图像测速仪（PIV）在水面上的速度估计是10%以上，比在现场观测收集到的水面以下10.05米。使用PIV观测驱动简单的推移质泥沙通量方程，我们解释了高达72%的下游泥沙通量的观测方差。这里描述的新方法提供了非侵入性的，高空间和时间分辨率的测量床和流量。
A new optical remote sensing technique for estimating water depth from an oblique camera view is described. The water surface and the bed were imaged simultaneously to create time‐dependent maps of the water surface velocities and the bed elevations that can be used to validate numerical models at high spatial and temporal resolution. The technique was applied in a sandy meander bend at the University of Minnesota Saint Anthony Falls Laboratory Outdoor StreamLab. The root mean square differences between optical estimates of the bed and in situ observations ranged between 0.01 and 0.03 m. Mean bed form wavelength was 0.73 m and mean crest height was 0.07 m, but both varied with distance around the meander bend. Bed form classification varied with distance downstream, and sinuosity of bed forms varied with local radius of curvature. Bed form roughness scaled similarly to other natural riverine environments although wavelength and height magnitude and variability were larger than predicted by empirical formulations for straight reaches. Bed form translation rate varied between 1 and 5 mm s−1. Estimates of velocity from particle image velocimetry (PIV) on the water surface were ∼10% higher than in situ observations collected ∼0.05 m below the water surface. Using the PIV observations to drive simple equations for bed load sediment flux, we explained up to 72% of the observed variance in downstream sediment flux. The new methodology described here provides nonintrusive, high spatial and temporal resolution measurements of both the bed and the flow.