民勤绿洲外围新月形沙丘宽高比与移动速率变化特证

Variation characteristics of width-height ratio and migration speed of barchans at the margin of Minqin oasis

对民勤绿洲外围新月形沙丘形态演变过程和移动规律的认识是当地防风固沙与生态建设的重要前提。本文通过野外实地测量和高分辨率遥感影像分析,探讨民勤绿洲外围上风向边缘区域内新月形沙丘形态参数之间及其与移动速率的关系。结果表明:(1)沙丘宽高比16 a来保持常数值16。(2)高大沙丘年均移动距离小于3 m,属中等移动速度,形态基本保持不变,仅在迎风坡基线、脊线和翼角处变化明显。低矮沙丘移动较快,年均移动距离大于10 m,属极快速移动速度。(3)沙丘顺风向移动速率反比于宽度,比例常数为718.52 m^(2)·a^(-1)。该区域新月形沙丘以快速移动速度为主,移动速率大于5 m·a^(-1),占比为52.63%。(4)沙粒在迎风坡侵蚀并在背风坡沉积的过程中,大沙丘保持形态稳定,移动缓慢。小沙丘形态变化剧烈,移动快速,沙丘发育有进一步缩小的趋势。

The understanding of the evolution process of barchan dune and its movement rate is an important prerequisite for wind prevention and sand fixation and ecological construction in Minqin oasis.Based on field measurement and high-resolution remote sensing image analysis,The study discusses the relationship between the morphological parameters of barchan dune and its movement rate in the upwind edge of Minqin oasis.The results show that:(1)The aspect ratio of the dunes remains a constant value of 16 in 16 years.(2)The average annual moving distance of the tall dune is less than 3 m,which is a medium moving speed.The shape of the tall dune is basically unchanged,and the change is obvious only at the baseline,ridge line,and wing Angle of the windward slope.Low dunes move fast,with an average annual distance of more than 10 m,which is an extremely fast-moving speed.(3)The downwind velocity of the dune is inversely proportional to its width,and the proportionality constant is 718.52 m^(2)·a^(-1).In this area,the barchan dune is dominated by fast-moving speed,which is greater than 5 m·a^(-1),accounting for 52.63%.(4)During the process of sand erosion on the windward slope and deposition on the leeward slope,large dunes maintain stable morphology and move slowly.Small dunes change dramatically and move rapidly,and the dunes tend to shrink in development.