黄河上游沙漠宽谷河段塌岸引起河道横向变化特征

Lateral variation properties in river channels due to bank failure along the desert valley reach of upper Yellow River

通过黄河上游沙漠宽谷河段现场考察及实测资料分析,依据河岸物质来源及组成将黄河上游崩塌河岸划分为粘性河岸及非粘性风沙堆积河岸两大类,前者可分为平面崩塌、弧形滑动崩塌和复合式崩塌3种类型,后者表现出非粘性河岸的表层滑移及平面崩塌两种形式。进一步以磴口、乌海河段为例,分析粘性河岸和风沙堆积河岸的塌岸特征,并结合近10年的遥感影像解译分析河岸线崩退变化规律,揭示塌岸引起河道横向变化特征。结果表明粘性河段的塌岸后退距离大于风沙堆积河段,局部河段短期出现凹退凸淤的动态岸线变化特点,但全河段长期仍然处于总体淤积的态势。

By means of field survey and measurement data analysis, the types of river bank erosion along the desert wide valley reach of the upper Yellow River can be classified into two types ： cohesive bank and non-cohesive sand ac- cumulation bank, according to the river bank material composition and the sediment source. The former type can be further classified into three subtypes： plane collapse, arc collapse and cantilever collapse, whereas the latter has two subtypes of erosion： surface sliding and plane collapse. Taking the Dengkou reach and the Wuhai reach for examples, and combining with remote sensing image interpretations for nearly 10 years, the shoreline variations are analyzed to reveal the lateral variation in the reaches due to bank failure. Results show that the bank collapse rate of cohesive bank erosion is greater than that of non cohesive sand accumulation bank erosion. In the short term, there appears to be for- mations of concave bank and accretion of convex bank in local bending channels, but in the long term, the whole reach tends to be in the overall trend of siltation. Therefore, the study has great significance to revealing the channel lateral deformation and the fluvial processes due to bank failure in the upper Yellow River.