Vegetative impacts upon bedload transport capacity and channel stability for differing alluvial planforms in the Yellow River source zone
Vegetative impacts upon bedload transport capacity and channel stability for differing alluvial planforms in the Yellow River source zone
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DOI：
10.5194/hess-20-3013-2016
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发表时间：
2016-07
影响因子：
6.3
通讯作者：
Zhiwei Li;Guoan Yu;G. Brierley;Zhaoyin Wang
中科院分区：
文献类型：
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作者：
Zhiwei Li;Guoan Yu;G. Brierley;Zhaoyin Wang
抽象。研究了黄河上游干流和支流河道稳定性梯度从曲流到分支、分支-辫状到全辫状的变化过程中，植被对推移质输移和河道形态动力学的影响。虽然区域地质和气候在整个研究区域是相对一致的，有一个明显的梯度，在河岸植被的存在和丰富的这些到达青藏高原（研究区域的海拔范围从2800至3400米a.s.l.）。目前，由于缺乏水文和野外资料，植被对黄河上游冲积河段河道平面形态和推移质输沙能力的影响尚不清楚。研究区河岸植被的类型和格局随地形类型的不同而不同，其中，分汊河段以乔木为主，曲流河段以草甸植被为主，分汊-辫状河段以草、草本和稀疏灌木为主，辫状河段无河岸植被。河床植被覆盖与推移质输沙能力之间的非线性关系是明显的，其中推移质输沙能力是最高的分支河段，大致其次是分支辫状河、辫状河和曲流河。河段推移质输沙能力与上游来沙的关系对河道稳定性有重要影响。分汊河段汛期（6 ~ 9月）推移质输沙能力远小于泥沙补给率，导致河床淤积和河道动态调整。再分支辫状河段和再分支河段的河道调整率不太明显，而曲流河段相对稳定（即，这是一个被动的蜿蜒河段）。
Abstract. The influence of vegetation upon bedload transport and channel morphodynamics is examined along a channel stability gradient ranging from meandering to anabranching to anabranching–braided to fully braided planform conditions along trunk and tributary reaches of the Upper Yellow River in western China. Although the regional geology and climate are relatively consistent across the study area, there is a distinct gradient in the presence and abundance of riparian vegetation for these reaches atop the Qinghai–Tibet Plateau (elevations in the study area range from 2800 to 3400 m a.s.l.). To date, the influence of vegetative impacts upon channel planform and bedload transport capacity of alluvial reaches of the Upper Yellow River remains unclear because of a lack of hydrological and field data. In this region, the types and pattern of riparian vegetation vary with planform type as follows: trees exert the strongest influence in the anabranching reach, the meandering reach flows through meadow vegetation, the anabranching–braided reach has a grass, herb, and sparse shrub cover, and the braided reach has no riparian vegetation. A non-linear relation between vegetative cover on the valley floor and bedload transport capacity is evident, wherein bedload transport capacity is the highest for the anabranching reach, roughly followed by the anabranching–braided, braided, and meandering reaches. The relationship between the bedload transport capacity of a reach and sediment supply from upstream exerts a significant influence upon channel stability. Bedload transport capacity during the flood season (June–September) in the braided reach is much less than the rate of sediment supply, inducing bed aggradation and dynamic channel adjustments. Rates of channel adjustment are less pronounced for the anabranching–braided and anabranching reaches, while the meandering reach is relatively stable (i.e., this is a passive meandering reach).