中文摘要：

在实测1：10000水下地形资料的基础上运用不同断面间距（200、400、800、1600和3200m）计算了三峡水库蓄水后坝下游宜昌至枝城河段的河道冲淤量，分析了宜枝河段常测固定断面布设的合理性．研究结果表明，该研究河段布置的51个常测固定断面基本能控制地形变化，有较好的断面代表性，可不进行断面加密；河槽槽蓄量采用锥体法和梯形法计算差异很小，两种方法均能满足要求；槽蓄量计算若要达到一定的精度，在弯道、汊道、河道急剧放宽和束窄的河段断面间距不宜过大．通过比较宜枝河段不同断面间距全河段河槽冲淤量（包括枯水、平滩和洪水河槽），认为对宜枝河段而言，断面间距不大于2倍河宽即能满足精度要求．

英文摘要：

On the basis of analyzing the measured topographic data, this paper utilizes the cross-section method to calculate the scour and silting amount of the river reach from Yichang, downstream of the Three Gorges Dam, to Zhicheng before and after the Three Gorges dam began to impound. The paper settles five different profile spacings, 200, 400, 800, 1 600 and 3 200 meters in the application of the cross-section method, and analyzes the rationality of fixed cross-sections arranged in the river reach. The results show that the fifty-one fixed cross-sections are very representative and can control the topographical change. So there is no need to add additional cross-sections. When the channel storage capacity calculated by the cone method is compared with the trapezoid method, the difference of them is very small and both methods can meet calculation requirement. The river profile spacing should not be too big under the circumstances of branching river with bend and river channel with extending and narrowing rapidly in order to ensure the calculation precision of the channel storage capacity. In the Yichang-Zhicheng river reach, the calculation precision can meet the requirement just when the profile spacing is less than double of the river channel width through comparing the results of the entire reach channel storage capacity with different profile spacings under the circumstances of low water, bank-full and flood water.