First of all, generally speaking, most river bank breaches are caused by floods. For example, 202 1, 1, the golden section of Fenhe River in the west of Shanxi Province burst due to flood. Because except those specially built concrete dikes, most of them are earth dikes. When water flows in the dam, only one side is slowly infiltrated, but once the water overflows the dam, it will seep into the dam from all directions and accelerate the erosion. Eventually, it leads to breach, and erosion is the main reason why the river bank is easily washed away by water. For land, the bearing capacity of soil mainly comes from the contact friction between soil particles, and water content is an important factor affecting this bearing capacity.

Second, after the soil is soaked in water, it expands when it meets water, and the friction and gravity between molecules decrease, which makes the dam lose strength and is easy to be washed out of cracks, and then water will enter the interior from the cracks, which will aggravate the erosion. If the water level of the river bank is too high at this time, the huge water pressure will even wash away the dam directly from the crack. So the quality of the dam is the key. So can high-strength concrete be used as a river embankment? In fact, the Three Gorges Dam and Gezhouba Dam in China are both built with high-grade concrete, but this method is not applicable everywhere. Because concrete is rigid and cannot be deformed, the bottom of concrete dam must be built on rock foundation. However, many river sections in China are based on soil, and the earth dams have large deformation capacity and cannot be built. But even if there is bedrock, its depth will be the key factor affecting the construction. For example, the soil cover thickness of the Yellow River section flowing through the Loess Plateau is 80 to 100 meters.

Thirdly, to replace earth dam with concrete, the soil layer of 100 m should be dug first, not to mention that a series of subsequent projects are carried out on the basis of 100 m, so it is too difficult to build. So, like the Yellow River, how to protect the riverbank from being washed away? Because the Yellow River flows through the Loess Plateau, a large amount of sediment is swept away by the river and accumulated in the gentle downstream basin, which leads to the elevation of the riverbed, and the higher the embankment is forced to build, the more dangers there will naturally be. In more than 2,000 years recorded in history, the lower reaches of the Yellow River were flooded by crevasses 1500 times. It's all about the sediment. As the old saying goes, blocking is better than dredging, and dredging is better than introducing. In the process of harnessing the Yellow River, two commonly used methods are to control water and attack sand, and to store clear water and brush muddy water. The former is to make the river run through by narrowing the river channel, thus enhancing the sediment carrying capacity of the river. As for storing clear water to brush muddy water, it is to wash the Yellow River with clear water from Huaihe River and wash the sediment into the sea to achieve the effect of sand removal. If there is less sand, the river bed can come down and it will be safe naturally.