Comparison of blockage factors in modelling the resistance of channels containing submerged macrophytes
Comparison of blockage factors in modelling the resistance of channels containing submerged macrophytes
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DOI：
10.1002/rra.854
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发表时间：
2005-07-01
影响因子：
2.2
通讯作者：
Green, JC
中科院分区：
文献类型：
--
作者：
Green, JC
历史上，含有植被的河道比例（称为阻塞系数）是通过三种方式确定的：横截面、表面积和体积。前两个版本是二维测量。同时，三维体积版本偏向于更深的区域。提出了没有此类限制的第四种阻塞因子：多截面阻塞因子。对 5 到 9 个横截面进行了采样，以确定 35 个含有丛生沉水植物毛茛亚属 Batrachium（水螅）的河流地点的四种堵塞因子版本。然后评估这四种措施作为河道植物抗性预测因子的能力。各个横截面的植被比例与河道河段的植被抗性关系不大，这主要是由于斑块形成的大型植物的高空间变异性。在每个地点测量的所有横截面阻塞系数的加权中值与植被抵抗力产生最强的关系，尽管这并不明显优于体积或表面积版本。使用表面积阻塞因子的阻力模型在形成席状大型植物物种的预测阻力和计算阻力之间给出了非常高的残差，并且该模型不太可能适用于基流以外的条件。同样，体积版本预计不适用于比本研究中测量的深度变化更大的地点。版权所有 (c) 2005 John Wiley & Sons, Ltd.
The proportion of a river channel containing vegetation (termed the blockage factor) has historically been determined in three ways: cross-sectional, surface area and volumetric. The first two versions are two-dimensional measures. Meanwhile, the three-dimensional volumetric version is biased towards deeper sections of a reach. A fourth version of the blockage factor is proposed that does not have such limitations: the multi-cross-sectional blockage factor. Between five and nine cross-sections were sampled to determine the four blockage-factor versions for 35 river sites containing the clumped submergent macrophyte, Ranunculus subgenus Batrachium (water-crowfoot). The ability of these four measures to act as predictors of vegetative Channel resistance was then assessed.The vegetated proportion of individual cross-sections was poorly related to the vegetation resistance of a channel reach, primarily due to the high spatial variability of patch-forming macrophytes. The weighted median of all cross-sectional blockage factors measured at each site produced the strongest relationship with vegetation resistance, though this was not significantly better than the volumetric or surface area versions. The resistance model using the surface-area blockage factor gave a very high residual between predicted and calculated resistance for a mat-forming macrophyte species, and this model is unlikely to hold for conditions other than baseflow. Likewise, the volumetric version is not expected to hold for sites that have more depth variability than those measured in this study. Copyright (c) 2005 John Wiley & Sons, Ltd.