中文摘要：

基于原型定位观测资料分析，结合河工动床模型试验和数学模型计算，研究了黄河下游河道的萎缩成因，并提出了河道萎缩的含义，以及表征河道萎缩的因素及其判别因子。研究表明，河道萎缩的根本原因是水沙过程变异与河道边界因素共同作用的结果；主河槽过水断面面积变化量、同流量水位变化量、河底平均高程抬升速率和横断面形态等可作为河道萎缩的表征因子。

英文摘要：

This paper explores the cause of river channel shrinkage at lower reaches of the Yellow River. The research was based on the analysis of antitype observation, mobile bed model experiment and mathematical model. The meaning, characteristic factors and discriminating factors of the channel shrinkage are also set forward in this paper. The research indicates that the basic cause of the river channel shrinkage is the combined action of runoff and sediment variations and channel border effect. The variance of main river channel＇ s area of overflow cross-section, variance of water level at the same flow quantity, average elevation rate of the riverbed and section aspect can be regarded as characteristic factors.