Geography [3 Mark Question Answer]

River meanders are bends of longitudinal courses. S-shaped meanders which are common to most rivers result when a channel-forms a curved path. These are the result of both erosion and deposition work of rivers.
Meanders generally form under conditions of a gentle slope and sufficient water in rivers. The river flow is diverted by an obstruction allowing the river to do lateral erosion work.

At this stage, the gradient is reduced, and the river flows more slowly. The middle course of the river begins when it leaves the mountains area and enters the plains. In the middle course, the energy required to transport the materials is just enough to drag large particles. Fine particles remain suspended in water, large particles are just dragged along the bed of the river and smaller ones are rolled down in the center. The river also gets widened as a result of a great volume of water and the impact of the load.

Waterfall: A waterfall is generally formed due to large differences in the rate of erosion. The smaller differences lead to formation of step-like features known as rapids. The water that falls down the edge of hard resistant rock may have at the bottom a soft rock. It is this soft rock that gets eroded fast and creates a hollow basin called plunge pool. Some of the world’s highest and best known falls are Angel Falls (986 m) in Venezuela and Yosemite fall (778 m), California, USA.

Various factors affect erosion, transportation, and deposition work of a river. Important factors include the following :

1. The velocity of water: Erosion and transportation are both maximum when velocity is high. Deposition, on the other hand, takes place when the velocity of water is low.
2. The volume of water: The larger the volume of water, the greater is the power of erosion and transportation. Deposition, on the other hand, takes place better when there is a reduced volume of water as well as when the load is greater.
3. Load: Load is the material transported by a river. A load of a river does all the work of erosion and deposition. Mass wasting, deepening of river valleys and formation of landforms depend on the load a river carries.

Deflation Hollows: Deflation involves the lifting as well as the blowing away of loose materials from the ground. The sands and pebbles are carried in the air or driven along the ground. The finer dust and sands may be deposited even outside the desert margins. Deflation results in the lowering of the land surface to create depressions called deflation hollows.

The chief landforms resulting from the deposition of a river are the following :

1. V-shaped Valleys : It is formed from a stream eroding downward, through a process, called down cutting. These valleys are formed in the initial stages of rivers and have steep slopes.
2. I-shaped Valley : In regions of hard rocks it develops almost vertically in an I-shape. River valleys are normally formed in areas of sufficient rainfall and where rocks are not very hard or resistant.