Why is the lower course of a river wide?
In the lower course there is an absence of large rocks and the river channel, being wider and deeper applies less friction to the flow. It is this absence of friction, which creates the smooth channel that allows the velocity of rivers to increase despite the more shallow gradient of the channel.
Why does a river get wider downstream?
As the river flows downstream it is joined by tributaries, increasing the volume of water, velocity and therefore its erosive power. This enables it to cut a deeper channel as it flows downstream. Downstream, the channel becomes wider as the gradient becomes more gentle leading to less vertical erosion.
Is the lower course of a river wide?
In the lower course, the river has a high volume and a large discharge. The river channel is now deep and wide and the landscape around it is flat. However, as a river reaches the end of its journey, energy levels are low and deposition takes place.
Why the river channel in the lower course tends to be wider than in the upper course?
Answer: The river channels in the lower course are wider than the upper course because at the upper course the speed is high and it starts to cut anything in its path and at the lower course, the speed is low so it starts to distribute in many directions and distribute useful sediments.
Why does the lower course decrease the speed of the river?
Answer: The base level of river is almost same as the sea level as river enters plains and approach sea. As there is not much difference in height, water speed reduces. At plains, rivers move in meanders instead of straight and this can reduce the speed as well.
What is seen in the lower course of the river?
Solution. Delta is seen in the lower course of the river.
Why did the river become wider?
The slope of a river decreases as it flows progressively downstream. Gravitational force is stronger uphill, but gentle in the lower course. The water tends to flow slowly due to higher water friction, hence the width increases. Towards the mouth, the gradient is lower, enabling water to flow on a wide surface area.
What determines the width of a river?
We posit that the cross-sectional geometry of fine-grained rivers is set by the threshold stress of cohesive bank-toe material, which forms the structural anchor of the riverbank (Fig.
What forms the lower course of a river?
Meanders usually occur in the middle or lower course, and are formed by erosion and deposition. As the river flows around a meander, centrifugal forces cause the water to flow fastest around the outside of the bend.
Why does the channel width and depth increase downstream?
Due to increased erosion and more added tributaries, the river channel increases in width and depth further downstream. This also increases the volume of water the river can hold.
What is lower course of a river?
The lower course of the river is where the it comes to meet the sea at the mouth, and starts at the relatively straightening path preceeding it, surrounded by flat land. Features of the Lower Course of Rivers: High Volume and Discharge – At the lower course of a river, the river is at its biggest volume capacity.
Why does velocity increase downstream?
Velocity increases as more water is added to rivers via tributary rivers. This means that less of the water is in contact with the bed of the river and the mouth so there is less energy used to overcome friction. Hence rivers flow progressively faster on their journey downstream.
Why is river in the lower course also known as Old Stage?
The Old Stage This means that the river has to work very hard to make its way to the sea.
What landforms are found in the lower course?
Meanders and ox-bow lakes Meanders usually occur in the middle or lower course, and are formed by erosion and deposition. As the river flows around a meander, centrifugal forces cause the water to flow fastest around the outside of the bend.
What erosion makes a river wider?
Lateral erosion makes a river wider. This occurs mostly in the middle and lower stages of a river.
Why do rivers rise from higher slope and flow towards the lower?
A river forms from water moving from a higher elevation to a lower elevation, all due to gravity. When rain falls on the land, it either seeps into the ground or becomes runoff, which flows downhill into rivers and lakes, on its journey towards the seas.
How does river depth increase downstream?
As the river flows towards the mouth, the gradient of the slope becomes less steep. Eventually the river will flow over flat land as it approaches the sea. As the river moves from the source to the mouth – both the depth of the river and the width of the river will both increase.
Why does river velocity increase downstream?
Why does the depth of a river decrease downstream?
It often flows over a series of waterfalls and rapids. As a river flows down steep slopes, the water performs vertical erosion . This form of erosion cuts down towards the river bed and carves out steep-sided V-shaped valleys. As the river flows towards the mouth, the gradient of the slope becomes less steep.
What is the main work of rivers in the lower course?
Answer. The volume of water in a river is at its greatest in the lower course. This is due to the contribution of water from tributaries. The river channel is deep and wide and the land around the river is flat.