内蒙古孔兑区叭尔洞沟风水交互侵蚀作用下河谷地貌的演化规律

Valley Landform Evolution under Aeolian-Fluvial Joint Erosion in the Baerdong River Basin in Inner Mongolia,China

以内蒙古孔兑区的叭尔洞沟中游河谷段为研究区,围绕风水交互侵蚀作用的动力特征和侵蚀过程中的地貌形态变化问题,在野外调查和资料收集的基础上,通过野外气象观测与径流小区实验、地形测量与遥感分析等技术手段,对河谷风水交互侵蚀的现代过程进行研究,定量分析河谷不同地貌部位的蚀积格局变化和河谷形态演变。研究发现:在风水交互侵蚀作用下,河谷中游的河床沙丘、谷坡沙丘、阶地沙丘、阶地切沟和冲积扇切沟等风水交互侵蚀的地貌类型以一年为周期发生着循环往复的侵蚀和形态变化。多年来,由于风力和水力周期性的强弱变化,这些交互侵蚀单元的地貌形态发生了规律性的演变,进而控制了叭尔洞沟中游河谷的形态变化,其形态演变主要表现在河道弯曲度、河道宽度、河道偏移方向、河床横剖面倾斜方向以及冲积扇大小和河谷沙丘迁移距离等形态特征上。该研究可为风蚀水蚀交错区的土壤侵蚀防治提供科学借鉴和指导作用。

The study area is located in the middle reaches of the Baerdong River in Inner Mongolia.This study focused mainly on the dynamic geomorphological evolution caused by aeolian-fluvial joint erosion.Based on the field work and collecting the related data,the meteorological observation,runoff plot experiment,topographic survey and remote sensing analysis were applied to study the modern process of aeolian-fluvial joint erosion.The change of erosion pattern of different landforms and the evolution process of valley morphology were quantitatively analyzed.The results showed that the geomorphic types in the middle reaches of the Baerdong River are mainly the dunes on the river bed,valley slopes and terraces as well as the gullies on the terraces and alluvial fans.The erosion and morphologic evolution of these landforms repeat circularly in a year.Because of the periodic changes of wind speed and water regime,these aeolian-fluvial jointly eroded units have evolved regularly and controlled the change of valley landforms in the middle reaches of the Baerdong River for many years.The morphological changes could be mainly manifested in the river curvature,width of the river channel,shifting direction of the river channel,tilt direction of transverse section of riverbed,size of the alluvial fans and the migration distance of the sand dunes in valley.The study results could be referred in further researching and controlling soil erosion in the aeolian-fluvial joint erosion area.