我们知道一般江河大堤和水库大坝的横截面如图1甲、乙所示.比较下面两图,不难发现,它们的共同之处都是上窄下宽,不同的是江河堤的迎水面坡度缓,背水面坡度陡,而水库坝则恰恰相反,挡水面坡度陡,背水面坡度缓.图11为什么江河大提与水库大坝都修成上窄下宽无论是江河大堤,还是水库 We know that the cross sections of general river embankments and reservoir dams are shown in Figure 1A and B. Comparing the following two figures, it is not difficult to find that their common features are narrow widths, but the difference is that the river embankment meets The slope of the water surface is gentle, and the slope of the back water surface is steep, but the reservoir dam is just the opposite. The slope of the retaining surface is steep, and the slope of the backwater surface is slow. Figure 11 Why the rivers and dams of the river are both built on the narrow width, whether it is a river embankment or a reservoir