乌兰布和沙漠沿黄河区域下垫面特征及风沙活动观测

为明确乌兰布和沙漠沿黄河区域下垫面特征与风沙活动特点,该文对该地区的沙丘形态、粒度特征、风速、输沙率与风沙流结构及其相互关系进行了野外调查与室内分析。结果表明:研究区横向沙丘平均宽-高比约为12.75。沙丘表面平均粒径与分选系数呈现出由丘间地至落沙坡逐渐减小的趋势,偏度则呈现出增大趋势。沙丘各部位粒度累计分布曲线均为正偏、单峰态分布。在净风与起沙风环境下,仅丘间地与沙丘顶部风速廓线呈对数形式分布;迎风坡坡脚处风速廓线多呈幂函数分布;落沙坡与背风坡坡脚处风速廓线分布形式不统一。无论在高风能环境下还是低风能环境下,从丘间地至背风坡坡脚,沙丘断面近地表风速呈减小(至迎风坡坡脚),增大(迎风坡坡脚至丘顶),再减小(丘顶至落沙坡),再增大(落沙坡至背风坡坡脚)趋势。沙丘顶部是风沙活动最为强烈的部位,沙丘各部位90%以上的输沙量集中到10cm高度以下;沙丘各部位的风沙流结构均服从三次函数分布。最后,该文针对该区域下垫面与风沙活动的特点和危害,提出相应的防治对策,以期对该区域风沙危害的防治提供参考。

Underlying surface characteristics and observation of blown-sand movement in Ulanbuh Desert along Bank of Yellow River

To understand the characteristic of the surface and the blown-sand movement of the Ulanbuh Desert along the Yellow River bank, the dune formations, sand particle granularity, sand flux and aeolian saltation structures were analyzed, and the results were displayed. 1) The rate of width to height of the transversal dunes in this area was about 12.75. 2) The mean sand particle diameter, sorting coefficient and skewness were decreased from the inter-dunes to the slip face; the grain size distribution on different positions of dune were all displayed positively biased and narrow unimodal. 3) Whether the wind speed exceed the threshold wind velocity, only the wind profile above the inter-dunes and that above the dune crest followed the logarithmic functions. In most of situations, the wind profile above the foot of stoss slope followed the power functions. The distributed functions of wind profile above the slip face and that above the foot of lee slope showed a chaotic situation. 4) In strong wind and gentle wind environment, the wind velocity were decelerated from the inter-dunes to the foot of stoss slope, accelerated from the foot of stoss slope to the dune crest, decelerated from the dune crest to the slip face again, and then accelerated from the slip face to the foot of lee slope. 5) More violent blown-sand movement displayed on the dune crest. More than 90% sand transport in aeolian saltation cloud concentrated below the height of 10 cm, and the profiles of aeolian cloud at different positions of dune followed the cubic functions. 6) There is a close feedback relationship existing between the surface and the blown-sand movement. At last, based on the observation, some suggestions for building proper aeolian hazard protection system in the Ulanbuh Desert along the Yellow River were proposed. This study can provide a reference for prevention of the aeolian hazard in this region.