Changes in the characteristics of a river and its valley Flashcards
How does the shape of the valley change as the river goes down stream
From a V to a more flat bottomed U
What are the 2 reasons for the shape of the valley changing as the river goes down stream
1) In highland areas, the river has the power to erode vertically due to gravity (vertical erosion). This creates the steep āVā shape
2) The river erodes sideways (laterally) further down stream due to the lack of gradient
How does the width change downstream
It increases
Why does the river widen downstream
Increased water from tributaries results in the river having more energy to erode the banks of the river making it wider.
How does the depth change downstream
It increases
Why does the river deepen downstream
The increased water from tributaries results in the river having more energy to erode the bed of the river making it deeper
How does the velocity change downstream
It increases
What are the 2 reasons why the river speeds up downstream
1) The water is slower near the source as it is shallower so more of the water is in contact with the bed and the banks, causing friction that slows the river down.
2) Further down stream, the river is deeper and wider, so less of the water is in contact with the bed and banks, and so there is less friction, as a result, the river flows faster
How does the discharge change downstream
it increases
Why the discharge increase down stream
The increase in the volume of water due to the river being joined by tributaries and the increase in velocity, results in a greater discharge
How does the gradient change downstream
It decreases
Why does the gradient decrease downstream
The slope will become less steep as the river moves out of the hills and into the flatter areas on its way to the sea.
