Living landscapes: Muddy and vegetated floodplain effects on fluvial pattern in an incised river
Living landscapes: Muddy and vegetated floodplain effects on fluvial pattern in an incised river
复制标题
DOI：
10.1002/esp.4437
复制
发表时间：
2018-08
影响因子：
3.3
通讯作者：
M. Kleinhans;B. de Vries;L. Braat;M. van Oorschot
中科院分区：
文献类型：
--
作者：
M. Kleinhans;B. de Vries;L. Braat;M. van Oorschot
粘性河漫滩沉积物和植被都被认为是造成曲流河型的原因。我们的目的是比较泥和植被对河流平面形态和形态动力学的单独和联合影响，在中等规模的山谷河流。我们使用一个数值模型的世纪尺度的模拟流，泥沙输运和形态再加上河岸植被定居，生长和死亡率的功能，流阻依赖的物种特征。通过过量剪应力关系并结合活性层配方来预测泥浆通量。我们发现，山谷洪水水位随着植被密度的增加而增加，导致更高的编织强度，而不是蜿蜒的趋势。洪水期间的剪应力在泥泞的洪泛平原表面刻出了通道。另一方面，较高的泥浆浓度会增加洪泛区的淤积，降低漫滩水流频率，并最终导致单线河道的形成。植被使淤泥存款到更靠近河道的地方作为堤坝，这表明淤泥沉积和植被沉降相互促进了漫滩的形成。然而，泥土和植被以两种方式抵消。首先，植被增强了河漫滩的加积，最终增加了高泥浆浓度的植物干燥。第二，植被增加了周期性的瀑布在山谷中截止的趋势。降落伞的切断在当地重新设置了景观，并为植被创造了新的机会之窗。令人惊讶的是，在具有高泥浆浓度的系统中，这导致植被覆盖的滞后环和延迟的泥浆沉积。解释古生代河流相的分歧是，即使是无根植被，捕获粘性泥更接近河道，形成较厚的河漫滩上的点坝，可以增强曲流的趋势，并在高泥供应，形成稳定的渠道。然而，在植被密度较高的狭窄河谷河流中，蜿蜒的可能性更小。深圳市恒威电子科技有限公司
Cohesive floodplain sediment and vegetation are both thought to cause meandering river patterns. Our aims are to compare the isolated and combined effects of mud and vegetation on river planform and morphodynamics in the setting of intermediate‐sized valley rivers. We use a numerical model for century‐scale simulation of flow, sediment transport and morphology coupled with riparian vegetation settlement, growth and mortality as functions of species traits on which flow resistance depends. Mud fluxes were predicted by excess shear stress relations in combination with the active layer formulation. We found that valley‐flooding water levels increase with vegetation density, causing a higher braiding intensity rather than meandering tendency. The shear stress during floods carves channels through the muddy floodplain surface. Higher mud concentration, on the other hand, increases floodplain aggradation, reduces the overbank flow frequency and ultimately causes formation of a single‐thread channel. Vegetation causes mud to deposit closer to the river channel as a levee, showing that mud sedimentation and vegetation settling mutually enhance floodplain formation. However, mud and vegetation counteract in two ways. First, vegetation enhances floodplain accretion, which ultimately increases plant desiccation for high mud concentrations. Second, vegetation increases the tendency of periodic chute cutoffs in valleys. The chute cutoffs locally reset the landscape and create new windows of opportunity for the vegetation. Surprisingly, in systems with a high mud concentration this causes hysteretic loops of vegetation cover and delayed mud deposition. Ramifications for the interpretation of Palaeozoic fluvial facies are that even rootless vegetation, capturing cohesive mud closer to the river channel to form thicker floodplain on the point bar, can enhance the tendency to meander and, under high mud supply, form stable channels. However, meandering is more unlikely in narrower valley rivers with higher vegetation density. © 2018 John Wiley & Sons, Ltd.