Fluvial Processes Flashcards
Why is the load bearing capacity of the water drastically reduced?
Due to the sluggish flow of water as a result of the gentle slope of land
Define a braided stream
▪︎ in the lower course of the river, there is excessive deposit of the land on the floor due to the sluggish flow of water and the reduced bearing capacity of the water.
▪︎ the streams which get divided into a network of channels, forming bars of sands and islands is known as a braided stream.
Why is the current of the river slowest at the sides and bottoms?
Because of retardation of friction
Define natural leeves
In the lower course of the river, the slightest slackening of speed at once, results in deposition so that silt accumulates at the bottom and the sides of the river.
After a long time, the bed of the river is raised and it flows between raised banks along a bed which is at higher level than the plains on the either side. Such a raised embankment or a bank is known as a natural leeve
What are artificial leeves
The man made leeves which are built upon the embakments of the rivers as a protection from floods is known as an artificial leeve.
Define a flood plain. Give examples
Natural leeves often save the surrounded areas from the further of floods. But when these leeves can’t take the excessive pressure of the river water, it floods the entire area surrounding it. Most of the sediments of the river gets deposited there after the flood is over. In this way a vast plain is formed known as a flood plain.
▪︎ examples - Mississippi, ganga etc have formed extensive flood plains
How is a delta formed?
When the river enters the sea or a lake, it deposits all the load at its mouth which leads to the formation of a delta
State the features of a delta in details.
▪︎ It is a triangular feature with this apex pointing upstream.
▪︎ marked as a fan-shaped area of fine alluvium.
▪︎ the Greek letter ‘Δ’ closely resembles the triangular delta of river Nile.
▪︎ the mud deposited along the banks of the river because of the slow carrying capacity, becomes an obstacle and divides the rivers into numerous branches called the distributaries.
▪︎ the development of such network of channels and sub channels extends the delta areas.
▪︎ the river has no alternative but to discharge it’s water sluggishly through these distibutaries.
▪︎ With constantly settling sediments , the delta grows vigorously as long as the water channels are not completely choked by silting.
Name one of the biggest deltas in the world
Ganga Brahmaputra delta (1,25,000 Sq km)
What are the conditions for building up a data?
▪︎ There should be large quantities of water in the upper stream of the river so that there is sufficient sediments available throughout the erosional work of the rivers.
▪︎ a large number of tributaries should join the main river so that additional sediment is available for the formation of delta.
▪︎ the river should have a long course so that the speed of the water is sufficiently reduced before it enters the sea. This is necessary for the deposition to take place near the sea.
▪︎ there should be no lake or any other obstruction in the course of the river because in that situation the river will deposit it’s sediment there and the sediment left out will not be sufficient for the formation of the delta.
