Characteristics Of Buried Paleoriver Channel In Yishui-Tangtou Section Of Yi River

The study of ancient channel has attracted more and more attention from experts and scholars.It is of great significance to understand the evolution history of river geomorphology in a region.At the same time,according to river characteristicsand riverbed evolution characteristics of study of ancient river can help river regulation,it also provides geological basis for river regulation and river crossing engineering construction.Therefore,this paper chooses the river of Yishui-tangtou section of YiheRiver as the main research area for analysis and research.In this paper,7 points are selected in Yishui-tangtou section of YiheRiver for engineering drilling and geophysical survey to obtain sample data.These seven points are Dragon king temple,Gegou rubber dam,Yinan bridge in YiheRiver,LK19 + 580 bridge in YiheRiver,Beishe rubber dam,Bashan rubber dam,Yishuinan bridge in river.Sorting the drilling data of the first six sections,and geophysical exploration was carried out in Zhuyang village section,and sections were excavated in Zhuyang village section and Yinan bridge.Some samples of age and grain size were collected.According to the drilling data and geophysical exploration results,the profile of the river channel with each section is drawn.The width-depth ratio of each section of the ancient channel and the longitudinal gradient of the channel are analyzed,the bending rate is calculated,and the river type of the ancient channel in the study area is determined.Based on this study,the following conclusions were drawn:(1)The width-depth ratio of ancient river channel in Yishui-tangtou section of YiheRiver is generally increasing,but increasing irregularly.In the study area,the width-depth ratio in the section of gegou rubber dam reaches maximum value of 102.4 and the minimum value of 40.9 is reached in zhuyang.The deepest level of bedrock in the section of ancient river channel is about60 m,and the widest point of river channel is 900 in the research area.(2)The average longitudinal gradient of ancient river channel in Yishui-tangtou section of YiheRiver is 1.500,0.360,1.030,1.460,0.020 and 4.950 respectively.The average longitudinal gradient is the largest between gegou rubber dam and zhuyang section and the smallest between Yinan bridge-Gegou rubber dam section of YiheRiver.(3)According to the calculation results of aspect ratio,longitudinal gradient and bending rate,the river type of Yishui-tangtou section of YiheRiver is determined as braided river by comparing the river type division of S.A.Shumm.According to the age analysis of the sample reach the sediment age of the paleochannel in the study area is the last glacial maximum.So the final result is obtained: the river type in the reach of the study area during the last glacial maximum is braided river.