Aeolian sediment transport rates in the middle reaches of the Yarlung Zangbo River, Tibet Plateau

Abstract

Aeolian sediment emission from surfaces and subsequent transport are important geological processes. The Tibet Plateau experiences strong aeolian activity in areas such as the Yarlung Zangbo River basin. The dust storms have caused grounding of aircraft, highway closures, and other consequences for the region's residents. However, few researchers have studied this activity, which means that little knowledge is available on aeolian activity to support efforts to mitigate or prevent aeolian disasters. We measured aeolian sediment transport in the middle reaches of the Yarlung Zangbo River from 2020 to 2021. Field observations showed spatial and temporal variation of the sediment transport rate, with the greatest aeolian sediment transport in spring and winter. The largest total aeolian sediment transport rate occurred over sandy desert, with the smallest emission by a floodplain grassland. The change in sediment transport rate with height followed an exponential function, but the coefficients differed among landscapes. The mean sediment transport rate was greatest above shifting sand near riverbanks (0.21 kg m^-1 d^-1), where the sand is exposed in the winter and spring, followed by shifting floodplain sands (0.13 kg m^-1 d^-1), and was lowest above a floodplain grassland (0.03 kg m^-1 d^-1). Mean grain size also decreased with increasing height above 0.25 m, with a minimum mean grain size (about 52.6 μm) at 3.0 m above a floodplain grassland, and maximum mean grain size (about 100.2 μm) at 3.0 m above a floodplain shifting sand surface. The spatial variation in sediment transport rates and grain size related to the proportion of fine particles in the surface material. By comparing the aeolian sediment transport over different landscapes, we found that river banks and floodplains, which had rich deposits of very fine sand, silt, and clay, were the major sources of dust in this region. Our results indicate that efforts to mitigate or prevent aeolian disasters require a focus on riverbank and floodplain deposits.

Keywords: Aeolian sediment transport rates; Field measurements; Surface conditions; Weather conditions; Yarlung Zangbo River.