When a river carrying a lot of sediment enters the ocean, if the underwater slope at the estuary of the river is gentle and the river speed is slowed down by the jacking effect of seawater, the sediment carried by the river will accumulate in front of the estuary and form a delta. The delta area is large, the soil layer is deep, the water network is dense, the surface is flat, the soil is fertile and prone to floods.
What are the conditions for the formation of estuary delta?
There are two conditions for the formation of the delta. First, there should be a certain sediment concentration in the river. Sand is the material basis of delta formation. For example, the Yellow River has a high sediment concentration, and the sediment is continuously transported to the Yellow River Delta, which makes the area of the Yellow River Delta expand continuously.
Secondly, the position of the estuary should be low and flat, the velocity of the river channel is slow, the sediment carrying capacity of the river channel is weakened, and sediment deposition forms a delta, so the delta is usually low and flat. On the other hand, if the sediment concentration of the river is small, the terrain drop near the estuary is large and the flow velocity is fast, it is difficult to form the estuary delta, such as Congo River in Africa, and there is no obvious delta formation.