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Reevaluation of the aeolian sand flux from the Ulan Buh Desert into the upper Yellow River based on in situ monitoring
- Tian, Shimin, Yu, Guo-An, Jiang, Enhui, Guo, Jianying, Li, Zhiwei, Wang, Yuanjian
- Geomorphology 2019 v.327 pp. 307-318
- case studies, deserts, dunes, eolian sands, monitoring, rivers, sand, vegetation, wind power, wind speed, China, Yellow River
- 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.