中文摘要：

冲积河流演变规律的认识长期以来一直以经验性或半经验半理论性为主,缺乏坚实的理论指导。冲积河流平衡理论的建立利用了河道形态自动调整变分原理,但这一理论在大江大河中的实际应用性尚未得到检验。以长江中下游的河道形态特征为研究对象,详细对比分析河流平衡状态下的理论河道形态与实际观测值的差别。分析结果表明,输沙函数的选取对河道平衡形态的理论结果有很大的影响;长江中下游河段实测河道形态数据,与由基于冲积河流平衡理论建立的推移质输沙函数计算得到的理论河道平衡形态接近程度最高,冲积河流平衡理论在长江中下游河流演变中具有很好的实际应用性。

英文摘要：

The understanding of river behavior has been mostly empirical or semi-theoretical without solid theoretical foundation. The equilibrium theory for alluvial channel flow is based on the variational principle,however,its applicability in the Yangtze River has not been examined. For the channel morphological characteristics along the middle and lower Yangtze River,this study compares in detail the theoretical equilibrium channel geometries with the actual measurements. It demonstrates： Sediment transport formulae have considerable effects on theoretical equilibrium channel geometries; The theoretical equilibrium geometries show the highest degree of consistence with actual observations,justifying the applicability of the equilibrium theory for alluvial channel flow in the middle and lower Yangtze River.