Reevaluation of the aeolian sand flux from the Ulan Buh Desert into the upper Yellow River based on in situ monitoring
Reevaluation of the aeolian sand flux from the Ulan Buh Desert into the upper Yellow River based on in situ monitoring
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DOI：
10.1016/j.geomorph.2018.11.009
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发表时间：
2019-02
期刊：
影响因子：
3.9
通讯作者：
Shimin Tian;Guoan Yu;E. Jiang;J. Guo;Zhiwei Li;Yuanjian Wang
中科院分区：
文献类型：
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作者：
Shimin Tian;Guoan Yu;E. Jiang;J. Guo;Zhiwei Li;Yuanjian Wang
风沙入河是影响沙漠地区河流泥沙动力学和河床演变的重要因素。关于风成沙输移的动力过程、控制因素及输移量的研究较少。本文以黄河上游乌兰布和沙漠东缘风沙流为例，研究了黄河上游风沙的运移规律。本研究基于2013年至2016年对风流动特征、风成沉积动力学（跃移、蠕动和悬浮）以及典型沙丘（移动的、半锚定和锚定）迁移的系统监测。确定了研究区风速与风沙输送的关系。当风速≥ 5.7m/s时，风沙运移速率（跃移和蠕动）与距地面2 m处风速的关系可用多项式表示，当风速<5.7m/s时，风沙运移速率与距地面2 m处风速的关系可用幂函数表示。沙丘迁移主要发生在3 ~ 5月，沙丘迁移速率受风速及沙丘高度、植被状况等因素的影响。计算了风沙流（颗粒跃移、蠕动和悬浮）和沙丘迁移的输沙速率，估算出2013、2014、2015和2016年入河风沙量分别为147、86、52和50万t/a。这些结果明显低于1980年代至2000年代的估计。近60年来，该地区风速的下降导致风沙输沙率的急剧下降，植被覆盖度的提高减少了活动沙丘和移动的沙丘的面积，黄河沿岸的堤防建设抑制了风沙向河道的迁移，从而减少了风沙通量。
Aeolian sand transport into rivers is a crucial factor influencing channel sediment dynamics and fluvial processes in rivers that flow through desert areas. Few studies have examined the dynamic processes, controlling factors, and the amount of aeolian sand transported into river channels. Here, we report a case study of aeolian sand transport into in the upper reaches of the Yellow River as it flows along the eastern margin of the Ulan Buh Desert, which is a major desert in northern China. The present study is based on systematic monitoring of wind flow characteristics, aeolian sediment dynamics (saltation, creep and suspension), and the migration of typical sand dunes (mobile, semi-anchored, and anchored) from 2013 to 2016. The relationship between wind speed and wind-blown sand transport in the study area was determined. The relationship between the rate of aeolian sand transport (saltation and creep) and the wind speed 2 m above the ground surface can be depicted with a polynomial relation when the wind speed is ≥5.7 m/s, and with a power function when the wind speed is <5.7 m/s. Dune migration mainly occurred during March to May, and the dune migration rate was influenced by wind speed and other factors such as dune height and vegetation conditions. The rate of aeolian sand transport by wind-blown sand flow (particle saltation, creep, and suspension) and sand dune migration were calculated, and the annual aeolian sand transport rates into the river channel in 2013, 2014, 2015 and 2016 were estimated to be 1.47, 0.86, 0.52, and 0.50 million t/yr, respectively. These results are significantly lower than previous estimates made between the 1980s and 2000s. The decrease in sand flux may be attributed to the regional decline in wind speed over the last six decades which has caused a sharp reduction of the aeolian sand transport rate, the improved vegetation coverage in this area which has reduced the area of active and mobile dunes, and an embankment constructed adjacent to the Yellow River which has suppressed aeolian sand migration into the river channel.