流动沙丘不同部位风蚀积沙特征研究

[目的]探究和利用流动沙丘各部位的风蚀积沙规律,为提升固沙技术措施提供依据。[方法]在典型新月型沙丘上设置3台光电子式积雪深度测定仪观测流动沙丘不同部位的风蚀和积沙规律。[结果]在特定风速下落沙坡随着起沙风速变化其积沙深度由1cm逐渐增加到12cm,并在起沙风速下降时形成一个强烈的积沙过程;迎风坡在起沙风速时处于最大的风蚀状态,并随风速变化形成一个由强风蚀到弱风蚀的转变过程;沙丘顶部在临近起沙风速时处于风蚀过程,并随起沙风速的逐渐增加又处于积沙过程。此外,流动沙丘迎风坡在12月至翌年5月间净风蚀深度月均值约为29.85cm;落沙坡在12月至翌6月间积沙深度月均值净增加139.5cm;而沙丘顶部在3—11月为风蚀发生期,平均风蚀深度变化值为27.3cm,12月至翌年3月为积沙发生期,平均积沙深度变化值为29.47cm。[结论]风速对流动沙丘不同部位风蚀积沙特征变化具有重要影响,而且不同部位风蚀积沙程度存在明显差异。

Characteristics of Wind Erosion and Accumulated Sand in Different Positions of Mobile Dune

[Objective] Exploration and utilizaton Study on the law of wind erosion and accumulated sand in different parts of mobile dune can provide the support for sand fixation technical measures on the desert combat.[Methods] Three instruments of photoelectron snow retention depth-sounder were set up in the typical crescent dune to determinate the wind erosion and accumulated sand process in different positions of mobile dune.[Results] The accumulated sand depth ranged form 1 cm to 12 cm gradually on sand falling slopes with the change of sand-driving wind velocity under the certain wind velocity scope. And the strong sand deposition process was observed when sand-driving wind velocity declined. Windward slope erosion was in the largest state at the sand-driving wind velocity. And the transition process from strong to weak wind erosion formed with the change of sand-driving wind velocity. The top of the dune was erosion process at the near sand-driving wind velocity. And accumulated sand process was found at the top of the dune with the gradual increase of sand-driving wind velocity. In addition, the monthly mean of net wind erosion depth on windward slope of mobile dune was 29.85 cm from December to next May. The monthly mean net increase of accumulated sand depth on the sand falling slope of mobile dune was 139.5 cm from December to next June. But the erosion occurrence at the top of the dune was found from March to November, and the change value of the average erosion depth was 27.3 cm. The accumulated sand occurrence was found at the top of dune from November to next March, and the change value of the average accumulated sand depth was 29.47 cm.[Conclusion] Wind velocity has the important influence on wind erosion and deposition characteristic change in different positions of mobile dune, and wind erosion and accumulating sand were obvious difference in different parts of mobile dune.