中文摘要：

黄河以其高含沙水流以及下游河道的高沉积速率而著称于世。迄今的研究．主要针对黄河中下游流域的侵蚀、水文泥沙和河床演变方面的研究，而对黄河流域主支流发生河型转化的现象关注不够。在黄河的不同河段，河型的变化频繁，类型多样，现象复杂，是研究者不可回避的科学问题。本文选取黄河上游第一弯的玛曲河段、黄河上游末段托克托附近河段及黄河下游高村上下河段来研究河型转化的形式及影响因素。玛曲河段沿流向发生网状河型→弯曲河型→辫状河型的转化现象．该系列转化呈现出由极稳定河型向极不稳定河型的转化．这与世界上通常可以观察到的沿流向不稳定河型向稳定河型转化的情况完全相反。这主要受到地壳的抬升、上下峡谷卡口、水动力特征、边界沉积物特征及植被的区域分布等因素的控制。托克托附近沿流向发生了弯曲河型→顺直河型转化的现象．这是较稳定河型向极稳定河型的转化．主要受到边界沉积物、水动力等因素的控制。高村上下河段沿流向发生的辫状河型→弯曲河型转化的现象．是由极不稳定河型向较稳定河型转化的现象．河道边界沉积物及水动力是其主要控制因素，人工大堤只是限制了河道摆动的最大幅度，对河型的性质影响不大．但其上游河段修筑的水库导致下泻的水流在辫状河段的侵蚀能力增强而使其边界沉积物粗化．并将泥质物大量沉积在弯曲河段．客观上促进了河型的转化。

英文摘要：

The Yellow River is famous in the world because of its high-concentrated flow and high sedimentary rate on the channel bed of the lower reach. The study on the Yellow River, hereinto, is mainly on erosion, hydrology, sediment delivery and channel bed evolution in the middle-lower reaches. It has not been sufficient to pay attention to the river pattern transformations in the main or tributary channels of the Yellow River. Frequent, various and complicated transformations of river patterns in different reaches of the Yellow River are scientific problems which cannot be blench for researchers. This study focuses on the river pattern transformations and their influence factors in the selected river reaches： Maqu reach, the first curve in the upper reach, Tuoketuo reach in the end of the upper reach, and Gaocun reach in the lower reach of the Yellow River. The river pattern transformations in the Maqu reach show changes from anastomosing to meandering and from meandering to braiding. The series transformations present a tend from very stable to very unstable channel patterns that is reverse to the normal trend from unstable to stable channel patterns in the world. These transformations are influenced by crustal rise, restriction of the gorges in upper and lower reaches, hydrodynamic characteristics, sediment characteristics of channel boundary and regional distribution of vegetation cover. The river pattern transformations in the Tuoketuo reach show changes from meandering to straight. That is the transformation from relative stable to very stable channel patterns. It is mainly influenced by the sediment characteristics of channel boundary and hydrodynamic characteristics. The river pattern transformations in the Gaocun reach show changes from braiding to meandering channel patterns. It presents a trend from very unstable to relative stable channel patterns. It is mainly influenced by the sediment characteristics of channel boundary and hydrodynamic characteristics. The artificial levees only restrict the maximum r