Integrating network topology metrics into studies of catchment-level effects on river characteristics
Integrating network topology metrics into studies of catchment-level effects on river characteristics
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DOI：
10.5194/hess-23-2305-2019
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发表时间：
2019-05-14
影响因子：
6.3
通讯作者：
Millington, James D. A.
中科院分区：
文献类型：
--
作者：
Heasley, Eleanore L.;Clifford, Nicholas J.;Millington, James D. A.
河网的空间布局是流域的一个基本特征，在流域水平效应和河段形态与生态之间起着管道的作用。然而，河网结构往往被简化，以反映河流特征从上游到下游的梯度，通常由河流顺序表示。这项研究的目的是使用两个网络密度度量来量化网络拓扑结构-一个表示距离上的网络密度，另一个表示高程上的网络密度-这两个度量可以很容易地从数字高程模型中提取，因此可以应用于全球任何集水区。这些指标应该更好地考虑到集水区的多维性质，而不是河流的顺序，并且在功能上适用于集水区的地貌、水文和生态属性。通过使用为法规遵从性收集的监测数据来评估指标的功能效用，以探索与网络拓扑相关的河流特征模式。利用英格兰河流生境调查数据库中的河流特征，该方法被应用于英国四个相对低能量的人为修改的集水区。将网络密度度量所解释的河流特征中的模式与作为拓扑学标准度量的河流顺序进行比较。结果表明，与流序相比，网络密度度量对网络拓扑结构提供了更丰富和功能更相关的描述，突出了每个流域内部网络结构在密度和空间布局上的差异。网络密度度量与河流特征之间的相关性表明，栖息地质量分数在所有流域都随着网络密度的增加而一致地增加。至于河流性质的其他指标--修改分数、水流类型速度和泥沙大小--不同的流域对这两个网络密度指标的反应是不同的。河流顺序与河流特征之间几乎没有显著的相关性，这突显了河流顺序在考虑网络拓扑方面的局限性。总体而言，结果表明，网络密度度量是更有力的度量，它在概念上和功能上提供了一种改进的方法来计算网络拓扑对河流系统的影响。
The spatial arrangement of the river network is a fundamental characteristic of the catchment, acting as a conduit between catchment-level effects and reach morphology and ecology. Yet river network structure is often simplified to reflect an upstream-to-downstream gradient of river characteristics, commonly represented by stream order. The aim of this study is to quantify network topological structure using two network density metrics - one that represents network density over distance and the other over elevation - that can easily be extracted from digital elevation models and so may be applied to any catchment across the globe. These metrics should better account for the multi-dimensional nature of the catchment than stream order and be functionally applicable across geomorphological, hydrological and ecological attributes of the catchment. The functional utility of the metrics is assessed by appropriating monitoring data collected for regulatory compliance to explore patterns of river characteristics in relation to network topology. This method is applied to four comparatively low-energy, anthropogenically modified catchments in the UK using river characteristics derived from England's River Habitat Survey database. The patterns in river characteristics explained by network density metrics are compared to stream order as a standard measure of topology. The results indicate that the network density metrics offer a richer and functionally more relevant description of network topology than stream order, highlighting differences in the density and spatial arrangement of each catchment's internal network structure. Correlations between the network density metrics and river characteristics show that habitat quality score consistently increases with network density in all catchments as hypothesized. For other measures of river character - modification score, flow-type speed and sediment size - there are varying responses in different catchments to the two network density metrics. There are few significant correlations between stream order and the river characteristics, highlighting the limitations of stream order in accounting for network topology. Overall, the results suggest that network density metrics are more powerful measures which conceptually and functionally provide an improved method of accounting for the impacts of network topology on the fluvial system.