Why are villages built on the convex banks of the river, and why do the rivers erode and accumulate

First of all, it is necessary to know that the convex bank concave bank is due to the geostrophic deflection force.

caused. Due to the geostrophic deflection force, the river is severely scoured on one bank, which causes it to threaten the foundation of the village (imagine that the area of land you live in is decreasing every day, how would you feel?). )。

In addition, the convex bank (also called the silt bank) will have a lot of river sediment (as opposed to the concave bank). Generally, the sediment of rivers is rich in heavy materials, which can be cultivated to feed the population.

The water flow here is relatively slow, not too urgent, suitable for building a small fishing village port.

I do not agree with the upstairs statement, the geostrophic deflection force will have a more obvious shaping effect on the terrain on a larger scale. Geostrophic deflection forces play a role in such small-scale river concave banks.

The general law of development of curved rivers is the erosion of concave banks and the siltation of convex banks, which is due to the impact of water flow on concave banks greater than that of convex banks (due to the presence of centrifugal force). In addition, due to the centrifugal force of the curved river section, the water flow is biased to the concave bank, and the water body itself is a balanced centrifugal force, so the water surface height close to the concave bank position will become higher, and then the horizontal ratio of the same river section will be reduced, which further causes the side layer water flow with less sand to rush to the concave bank (conducive to scouring), and the underflow with more sand content rushes to the convex bank (conducive to siltation), which is the effect of transverse circulation. The next statement is similar to that of the second floor, due to the unstable ground of the concave bank, it will erode and retreat, which is not conducive to the construction of the village.

Shoals and deep troughs: When the river has a bend, due to the reflection of the water flow, a transverse circulation is formed in the interior of the river, and the transverse circulation continuously erodes the side of the concave bank, and the sediment carried by it accumulates on the side of the convex bank. During flooding, the flow rate of the long and narrow river surface is slow, the water flow ratio is small, the carrying capacity is weakened, and the sediment carried is deposited into shallows, and the wide river surface flow rate is fast, the water surface ratio is large, and the erosion ability is strong, forming a deep trough.

In addition, the confluence of the main currents may also form shoals and deep troughs. In summary, a shoal refers to the earlier part of the riverbed, and a deep trough refers to the deeper part of the riverbed.

Potholes and sills: Potholes are deep holes formed by the bedrock of the riverbed washed by the current, with smooth walls, often located below waterfalls. Rock sills are waterfalls and falls formed by the harder rocks in the bedrock riverbed across the bottom of the riverbed.

Meandering and braided flows: On the plane, the riverbed is straight, curved and divided, among which the curved riverbed is called meandering and the divided riverbed is called braided flow.

For the specific content and the causes of various landforms, please refer to the "Principles of Geomorphology" by Yang Jingchun and Li Lili

Peking University Press.