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首页> 外文期刊>Earth Surface Processes and Landforms: The journal of the British Geomorphological Research Group >The effects of survey frequency on estimates of scour and fill in a braided river model
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The effects of survey frequency on estimates of scour and fill in a braided river model

机译：勘测频率对辫状河模型冲刷和填充估算的影响

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摘要

Estimates of scour and fill in rivers that are derived by differencing topographic surfaces are known to be negatively biased by local compensation of scour and fill between surveys but the magnitude of bias is not well known. This study examines the effect of survey frequency on volumes of scour and fill over a period of active channel braiding in a small-scale river model. A 100 min, high temporal resolution time series of digital elevation models is artificially coarsened by selectively removing models. The resulting four overlapping time series have survey intervals of 10 min, 20 min, 50 min and 100 min. Cumulative scour and fill volumes for the 100 min period are compared between the four series. It is concluded that the decay in measured volumes of scour and fill with increased survey interval can be described using inverse functions. Cumulative scour-fill volumes are approximately 420 per cent greater over the study period for 10 min survey intervals than for a 100 min interval. After the 100 min period of competent flow, nearly 65 per cent of the channel area experienced significant compensation of scour and fill. Several compensation mechanisms were identified in association with braided channel kinetics, including lateral channel migration, the migration of bed forms, and channel avulsion. It is demonstrated that by negatively biasing scour, fill and net estimates, this error significantly affects morphological approaches to the estimation of bed load sediment transport.
机译：已知由不同地形地表得出的河流冲刷和填埋量估算值在两次调查之间因局部冲刷和填埋量补偿而具有负偏倚，但偏倚的程度尚不明确。这项研究考察了在小规模河流模型中，在主动河道编织过程中，调查频率对冲刷量和填充量的影响。通过有选择地删除模型，可以人工粗化100分钟，高时间分辨率的数字高程模型的时间序列。所得的四个重叠时间序列的调查间隔分别为10分钟，20分钟，50分钟和100分钟。比较这四个系列在100分钟内的累积冲刷量和填充量。结论是，可以使用反函数描述测量的冲刷量和填充量随测量间隔的增加而下降。在研究期内，调查间隔10分钟的累积冲刷量大约比100分钟间隔大420％。经过100分钟的有效流动之后，近65％的通道面积经历了冲刷和填充的明显补偿。确定了几种与编织通道动力学相关的补偿机制，包括横向通道迁移，床形迁移和通道撕脱。结果表明，通过对冲刷量，充填量和净估算值造成负偏，该误差显着影响了估算床荷输沙量的形态学方法。

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