中文摘要：

运用河流动力学理论，推求出整治水位下河槽在冲刷前、后航深变化值的表达式，对表达式的理论分析结果表明，在三峡水库下泄清水冲刷的条件下，通过守护关键可动洲滩，控制航槽不向两侧展宽，同时控制航槽内低矮的洲滩不被冲蚀，使清水冲刷只向纵向发展，就能达到增加航深的目的，这正是守护型控导工程对改善航道条件的积极作用所在。以长江中游荆江藕池口河段和太平口河段为例，计算了这两个河段守护关键可动洲滩后航深的变化值，模型计算值与实测断面概化后得到的航深变化值基本一致，进一步验证了守护型工程实现航道改善的作用。

英文摘要：

Based on the river dynamics theory, we derived a mathematical expression of waterway depth variation before and after erosion of the channel at regulation stage. Then, the theoretical analysis of the expression showed that waterway depth could increase. Under the erosion of the release of clear water from the Three Gorges Reservoir, in order to make the release of clear water only erode vertically, it is necessary to take several measures, that is, protecting key movable bottomlands, controlling dredged channel（not broadening in both sides）, and protecting low bottomlands from erosion in dredged channel. Thus, protective control works play a positive role in improving waterway condition. Taking Ouchikou and Taipingkou segments of the Jingjiang River at the middle reach of the Yangtze River as examples, we computed the variation of waterway depth in both segments after protecting key movable bottomlands. The model derived results are in accordance with the variation of waterway depth resultant from generalized measured profile, which further verifies the effect of protective control works on improving the waterway condition.