First to define what exactly is a river. Rivers are water bodies or simply stream of moving water that generally moves from a higher level to lower level. Level suggests the elevation degree. On its way down, when it continues flowing it is further joined by other, streams, water bodies. They play a very important part in the water cycle, acting as drainage channels for surface water. Rivers drain nearly 75% of the earth’s land surface.
Now coming to the stages of the river.
There are three stages:
1) The Young Stage:
The river is usually small and flows down steep slopes with lots of energy. The features found in the youthful stage of a river are all formed by the processes of Erosion. In its youthful stage, the river has very little power to erode. It undergoes vertical erosion while climbing down. This leaves steep sides which are exposed to weathering which in turn loosens and eventually breaks up the rock and soil. As a result, when it meets with obstacles of hard rock it is unable to cut through them and so has to flow around them. This leaves interlocking spurs of high ground jutting out on both sides of the valley.
2) The Mature Stage
In this stage, the slope becomes gentler than the previous and the river becomes much wider as it is joined by many tributaries. Not only that, the river is also carrying a load now that has been eroded from further upstream. Bends or menders are formed that are mainly due to the falt land and inward erosion taking place. Erosion will take place, while on the inside of the bend the current flows more slowly so Deposition will take place.
3) The Old Stage
You can call the river that it is at its old stage when you know it is in its wildest form. The land is also at its flatter than it has been ever before. Floodplains are almost flat plains of land which lie at the sides of rivers that are in their old stage This means that the river has to force its way to make its way to the sea. The main agent at work now is Deposition. During times of flooding, there will be an increase in the speed and volume of a river. Therefore when a river comes to a tight meander that it cannot go around it simply bursts its banks and cuts through the bend.