Hydrology, sediment transport dynamics and geomorphology of a variable flow river: the Mfolozi River, South Africa
Hydrology, sediment transport dynamics and geomorphology of a variable flow river: the Mfolozi River, South Africa
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可变流量河流的水文、泥沙输送动力学和地貌：南非姆弗洛齐河
DOI：
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发表时间：
2012
期刊：
影响因子：
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通讯作者：
W N Ellery
中科院分区：
文献类型：
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作者：
SE Grenfell;W N Ellery
Mfolozi河流量年际变化系数极高，达79%。流量频率的分析表明，径流量偏向于低流量值，一些非常大的洪水事件发生在直方图上的离群值。Mfolozi河的径流变化可能与多种因素有关，包括大的集水面积、干燥的冬季和潮湿的夏季的季节性气候、集水区的万年青植被、多变的降水和区域普遍气候振荡的发生。这项研究旨在解决如何径流变化对泥沙输移，从而地貌的影响。结果发现，泥沙输运的变异性发生在年内和年际尺度。月平均含沙量和流量的分析表明，滞后效应，使泥沙浓度达到峰值之前，在雨季早期排放。在湿季后期，最高流量往往有意想不到的低泥沙浓度。此外，数据表明存在长期滞后现象，这可能与十年尺度的气候振荡有关，气候振荡改变了沉积物的可利用性和河流容量，导致2000年流量达到峰值，2005年沉积物浓度达到峰值。然而，需要更多的数据来证实这种关系。径流的变化似乎与泥沙输运的变化有着因果关系，因为两者都与降水的变化以及由此产生的对植被生长和蒸散率的影响有关。径流和泥沙输运的变化对河流和洪泛区地貌有影响，在解释其地貌时应考虑可变河流的水文。
The co-efficient of variation for inter-annual streamflow of the Mfolozi River is extremely high at 79%. An analysis of flow frequency indicated that streamflow is skewed towards low-flow values, with a number of extremely large flood events occurring as outliers on the histogram. Streamflow variability in the Mfolozi River may be linked to multiple factors including a large catchment size, a seasonal climate of a dry winter and wet summer, evergreen vegetation in the catchment, variable precipitation and the occurrence of regionally pervasive climatic oscillations. This research aimed to address how streamflow variability impacted upon sediment transport and thus, geomorphology. It was found that sediment transport variability occurred at the intra- and inter-annual scale. Analysis of mean monthly sediment concentration and discharge showed a hysteresis effect, such that sediment concentration peaked prior to discharge in the early wet season. During the late wet season, peak discharges often had unexpectedly low sediment concentrations. Furthermore, data suggested the existence of long-term hysteresis that may be related to decadal-scale climatic oscillations that alter sediment availability and stream capacity, resulting in discharge peaking in 2000 and sediment concentration in 2005. However, more data are required to confirm this relationship. Variability in streamflow appears to share a causal relationship with sediment transport variability, as both are linked to variation in precipitation and the resultant impacts on vegetation growth and evapotranspiration rates. The variability of streamflow and sediment transport has implications for stream and floodplain geomorphology, and the hydrology of variable rivers should be considered when interpreting their geomorphology.