长江三峡地区数字地貌特征及对古分水岭位置的指示  

The Geomorphic Indices of the Three Gorges Area and Their Indication to the Location of Paleo-divide

作　　者：代彬 刘彧 王世杰[1,3] 胡传辉[1,2] DAI Bin;LIU Yu;WANG Shijie;HU Chuanhui(State Key Laboratory of Environmental Geochemistry,Institute of Geochemistry,Chinese Academy of Sciences,Guiyang 550081,China;University of Chinese Academy of Sciences,Beijing 100049,China;Puding Karst Ecosystem Research Station,Chinese Academy of Sciences,Guizhou Puding 562100,China)

机构地区：[1]中国科学院地球化学研究所环境地球化学国家重点实验室,贵阳550081 [2]中国科学院大学,北京100049 [3]中国科学院普定喀斯特生态系统观测研究站,贵州普定562100

出　　处：《地球与环境》2022年第5期676-690,共15页Earth and Environment

基　　金：中国科学院战略先导研究项目(XDB40020300);贵州省高层次创新型人才培养计划“十”层次人才项目(黔科合平台人才[2016]5648)。

摘　　要：三峡贯通一直是长江演化研究中亟待解决的核心问题之一,其古分水岭位置长期备受争议。本研究基于30 m分辨率的数字高程模型(DEM),以长江三峡万州-宜昌河段及其17个子流域为研究对象,采用地形分析、χ分析等方法,计算和分析了该地区的地形起伏、河道陡峭指数、流域面积高程积分和河流裂点等参数,综合讨论了三峡地区水系特征及古分水岭位置。χ-plot、面积高程积分结果表明三峡地区的河流基本处于非均衡状态,大多数河流都处于壮年期。三峡地区44个裂点主要分布在海拔200~800 m范围内。在巫山东侧水系中只发育一期低海拔坡断型裂点(200~600 m),而其西侧水系中普遍存在两期坡断型裂点(200~600 m, 800~1 200 m)。并且巫山地区χ值最低、子流域面积高程积分最高(>0.6),表明该地区河流侵蚀能力最强、流域最年轻。以上数字地貌特征指示巫山地区可能曾是三峡的古分水岭。本结论有助于认识三峡地区水系和地貌演化历史,并为进一步研究三峡贯通问题(如贯通时间、贯通方式)奠定基础。The connection of the Three Gorges has been one of the key problems need to be solved in the evolution study of the Yangtze River, and its paleo-divide location has been debated for a long time. In this study, the fluvial characteristics and the paleo-divide location of the Three Gorges were discussed based on the 30 m resolution digital elevation model(DEM) in the reaches between Wanzhou and Yichang of the Yangtze River and 17 sub-watersheds in the Three Gorges area by using methods like topographic analysis and χ-analysis to study some geomorphic indices including hypsography, the normalized channel steepness index(k), hypsometric internal(HI) and river knickpoints. The results of χ-plot and hypsometric internal indicate that the rivers in the Three Gorges area are basically in a disequilibrium state and most of the rivers are in the mature stage. In the Three Gorges area, 44 knickpoints are mainly distributed in the elevation of 200~800 m. Only one stage slope break knickpoints(200~600 m) are mainly developed in the rivers of eastern Wushan, while two stage of slope break knickpoints(200~600 m, 800~1200 m) generally existed in the rivers of western Wushan. Besides, lowest χ value and highest hypsometric integrals(>0.6) of sub-watershed around the Wushan area suggest that this region has a strong river erosion capacity and these basins are in a youthful stage. These geomorphic indices suggest that the Wushan area was once the paleo-divide of the Three Gorges area. This conclusion is helpful to understand the evolution history of river system and landscape in the Three Gorges area, and to establish a foundation for the further study on the connection of the Three Gorges(such as connection time and ways).

关 键 词：χ分析 面积高程积分 河道陡峭指数 古分水岭 长江三峡 

分 类 号：P931[天文地球—自然地理学] P951