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首页> 外文期刊>Journal of the American Water Resources Association >SPATIAL VARIABILITY OF POOL-TAIL FINES IN MOUNTAIN GRAVEL-BED STREAM AFFECTS GRID-COUNT RESULTS
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SPATIAL VARIABILITY OF POOL-TAIL FINES IN MOUNTAIN GRAVEL-BED STREAM AFFECTS GRID-COUNT RESULTS

机译：山地砾石流影响网格计数结果的尾矿细度的空间变异性

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摘要

Fine sediment (<2 and <6 mm) particles underlying a 49-intersection grid placed on a streambed at 25, 50, and 75% of the wetted pool-tail width are commonly counted to assess the status and trend of aquatic ecosystems or to monitor changes in the supply of fines in mountain gravel-bed streams. However, results vary even when crews perform nearly identical procedures. This study hypothesized that spatial variability of pool-tail fines affects grid-count results and that a sampling scheme can be optimized for precision and accuracy. Grid counts taken at seven evenly spaced locations across the wetted width of 10 pool tails in a pool-riffle study stream indicated a bankward fining trend with secondary peaks of fines within the stream center. Sampling locations close to the waterlines harbored more than twice as many fines as central locations. Most of the five grid-count schemes derived from the seven sampled locations produced significantly different results. Compared with sampling at all seven locations, schemes that focus near waterlines overpredicted fines, while those that focus on the center underpredicted them. Variability of fines among pool tails was the highest within a broad band along the waterlines; hence, focusing sampling there yielded the most variable results. The scheme sampling at 25, 50, and 75% of the wetted width had the lowest precision and moderate accuracy. Accuracy and precision of grid-count results can be greatly improved by sampling at seven even-spaced locations across the pool tail.
机译：通常将49交叉网格下面的细沉积物（<2和<6 mm）颗粒放在流化池尾宽度的25％，50％和75％的流床上，以评估水生生态系统的状况和趋势，或者监测山砾石床溪流中细粉供应的变化。但是，即使机组人员执行几乎相同的程序，结果也会有所不同。这项研究假设，池尾细粉的空间变异性会影响网格计数结果，并且可以针对精度和准确性优化采样方案。在水池浅滩研究流中，在10个水池尾部的湿润宽度上的七个均匀间隔的位置进行的网格计数表明，在河床中心存在细化的趋势，即细粉的次高峰。靠近水线的采样地点的罚款是中心地点的两倍多。从七个采样位置得出的五个网格计数方案中的大多数产生了明显不同的结果。与在所有七个地点进行抽样相比，关注水线附近的方案高估了罚款，而关注中心水域的方案则低估了罚款。沿池水线的宽阔区域中池尾之间的罚款变化最高；因此，集中采样在那里产生的结果最多。该方案在润湿宽度的25％，50％和75％处采样时，精度最低，中等精度。通过在池尾的七个偶数间隔位置进行采样，可以大大提高网格计数结果的准确性和精度。

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