雅鲁藏布江米林河谷风沙活动带动态与发育模式

Aeolian sand belt is typical wind erosion – aeolian landform, which is defined as a three-dimensional channel that composed of sidewalls and channel bottom, where aeolian sands are eroded, transported and deposited. It is widespread distributed on the valley floor of the Mainling valley, and serves as an important component of aeolian sand landforms in the Yarlung Zangbo River Valley. However, there has been limited detailed and systematic analysis of the aeolian sand belt concerning their morphometric features and evolutionary process. Therefore, we select the Mainling valley (between Lang county and Pai town) as the study area, (i) to do detailed measurement of the aeolian sand belt of its length, width, depth and dunes of its size, dune spacing, crest length, crest orientation and defect density in the field and via remotely sensed images, to study the morphometric characteristics and its variations of these aeolian sand belts, and (ii) by detailed measurement of the airflow and sand flux transport rate within the channel and on the dune, to analyze the rations of the aeolian dynamics and the geomorphology of the channel and dunes, and finally (iii) based on the long-term variations of the morphometric features of the aeolian belt, the rations of the aeolian dynamics with channel and dune morphometric features, and the analysis of the grain sizes and mineral compositions of sediments, wind regime, temperature and vegetation, to reveal the geomorphic evolution of the aeolian sand belts. This work thus may shed some light on the complementary of theories of aeolian sand landforms in the river valley.

风沙活动带是一种由风蚀沟槽和槽内沙丘组成的风蚀-风积地貌系统，广泛分布在雅鲁藏布江米林河谷，是雅鲁藏布江河谷风沙地貌的重要组成部分。然而，目前对这种以风蚀为基础、内部发育风积地貌的风沙地貌类型的形态和动力学研究相对较少。本项目拟在雅鲁藏布江米林河谷，采用地面测量、定位观测与遥感监测相结合的方法，从形态学和动力学角度出发，对米林河谷风沙活动带，包括风蚀沟槽、沙丘和沙丘群进行表面气流、输沙率、侵蚀堆积、形态变化等过程的观测、监测和分析，探讨风沙活动带的形态发育模式，为完善河谷风沙地貌理论做出贡献。

雅鲁藏布江河谷存在典型的“风沙活动带”。尤其是河谷上游马泉河、中游山南河谷和下游米林河谷的“风沙活动带”各具有独特的发育模式。本项目在雅鲁藏布江米林、山南和马泉河河谷，采用地面测量、遥感监测和中尺度数值模拟相结合的方法，从形态学和动力学角度出发，对雅江河谷“风沙活动带”的沉积物和风场特征进行分析，初步揭示了雅鲁藏布江河谷风沙地貌的发育模式。.（1）雅鲁藏布江不同河谷段风沙地貌各具特色；米林河谷段“风沙活动带”的发育模式：不规则分布的抛物线沙丘群→ 孤立的沙丘、沙丘链→ 规则分布的复合沙丘群。.（2）中尺度MM5气候模式显示，狭谷段由“束缚管道风”主导；宽谷段，大尺度风场叠加山谷风，河谷风沙地貌普遍发育。.（3）沉积物粒度分析显示，马泉河谷以非饱和侵蚀风沙流为主，山南河谷以物质堆积为主，米林河谷为风蚀-风积复合动力系统。.（4）风沙沉积物粒度和元素具有空间相关性，揭示不同河段风成沙物源一致，来自雅鲁藏布江北岸的长英质岩石和缝合线弧前盆地。河谷现代风成沙发育由风-水动力、物质迁移系统主导。