By the analyses of the field observed data it is found that the above-mentioned phenomenon is caused by the following factors , ( 1 ) The bed elevation of Tongguan serves as a local base level to the lower Wei.
文中利用渭河下游河道的实测资料，对比兴建三门峡水库前后以及三门峡改建前后渭河下游河道的横向演变，得到如下几点认识：（１）侵蚀基准面的变化是引起渭河下游河道横向摆动的主要因素；（２）洪水比降变平，相应河道弯曲系数变大，河道由稳定型向摆动型发展；洪水比降变陡，相应河道弯曲系数变小，河道由摆动型向稳定型发展；（３）滩地的泥沙组成代表河岸的可动性。