Sediment dynamics across gravel-sand transitions: Implications for river stability and floodplain recycling
Sediment dynamics across gravel-sand transitions: Implications for river stability and floodplain recycling
复制标题
砾石-沙过渡区的沉积物动态：对河流稳定性和洪泛区回收的影响
作者：
Gautam D
砾石-砂过渡（GST）是沿着常见的现象。它的特点是突然减少中位粒径，从砾石到砂大小的沉积物，并通过在沙输运模式从冲刷负荷为主的悬浮床物料负荷的转变。我们记录的变化，在通道的稳定性，悬浮泥沙浓度，通量和粒度的GST的Karnali河，尼泊尔。在GST上游，砾石床河道在一百到一千年的时间尺度上保持稳定。下游，漫滩沉积物被改造的侧向银行侵蚀，特别是在季风排放。悬浮泥沙浓度，粒度和通量显示违反直觉的增加下游的GST。结果表明，在整个GST的通道动态发生了巨大的变化，从相对固定，陡峭的砾石床河流，不经常撕拉低梯度，相对移动的砂床渠道。泥沙浓度和近床悬浮颗粒粒径的增加可能是由于河道流动性增强，促进了河床和河岸物质之间的交换。这些结果带来了新的限制，在山前的通道稳定性，并表明，时间和空间有限的泥沙通量测量下游的GST更能说明流阶段和河漫滩回收比大陆尺度的泥沙通量和剥蚀率的估计。
The gravel-sand transition (GST) is commonly observed along rivers. It is characterized by an abrupt reduction in median grain size, from gravel-to sand-size sediment, and by a shift in sand transport mode from wash load–dominated to suspended bed material load. We documented changes in channel stability, suspended sediment concentration, flux, and grain size across the GST of the Karnali River, Nepal. Upstream of the GST, gravel-bed channels are stable over hundred-to thousand-year time scales. Downstream, floodplain sediment is reworked by lateral bank erosion, particularly during monsoon discharges. Suspended sediment concentration, grain size, and flux reveal counterintuitive increases downstream of the GST. The results demonstrate a dramatic change in channel dynamics across the GST, from relatively fixed, steep gravel-bed rivers with infrequent avulsion to lower-gradient, relatively mobile sand-bed channels. The increase in sediment concentration and near-bed suspended grain size may be caused by enhanced channel mobility, which facilitates exchange between bed and bank material. These results bring new constraints on channel stability at mountain fronts and indicate that temporally and spatially limited sediment flux measurements downstream of GSTs are more indicative of flow stage and floodplain recycling than of continental-scale sediment flux and denudation rate estimates.
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供应有限的河床形态和砾石-砂过渡下游的扩展
影响因子：
3.5
作者：
J. Venditti;J. Nittrouer;M. Allison;R. Humphries;M. Church
通讯作者：
M. Church
砾石-砂转变：扩散延伸中的沉积物动力学
DOI：
--
发表时间：
2015
期刊：
影响因子：
--
作者：
J. Venditti;N. Domarad;M. Church;C. Rennie
通讯作者：
C. Rennie
DOI：
--
发表时间：
1938
期刊：
影响因子：
--
作者：
H. Rouse
通讯作者：
H. Rouse
印度比哈尔邦北部印度恒河平原的河流系统及其沉积通量
影响因子：
3.5
作者：
R. Sinha;P. Friend
通讯作者：
P. Friend
影响因子：
64.8
作者：
Dingle, Elizabeth H.;Attal, Mikael;Sinclair, Hugh D.
通讯作者：
Sinclair, Hugh D.