RIVER LONG PROFILE & FLOOD DEFENCES Flashcards
Describe three features of the shape of the river channel in its upper course.
It is narrow, shallow and has a small wetted perimeter.
What is meant by the term wetted permitter.
It is the length of the rivers bed and banks added to together.
Describe the roughness of the river wetted perimeter in its upper course.
It has a very rough wetted perimeter as many large rocks and boulders protrude from its bed and break the surface of the water.
Describe the downstream gradient of the upper course of the river.
It has a very steep gradient.
What is meant by the term laminar flow?
Laminar flow is when the water flows parallel to the rivers bed.
What is meant by the term turbulent flow?
Turbulent flow is when water flows in eddies downstream.
Explain why the upper course of a river has a low velocity.
It has a low velocity because the river looses a lot of its energy over the friction caused by its rough bed and banks.
Describe how the length of a rivers wetted perimeter changes down its long profile.
Its length increases.
Describe how the velocity of a river changes down its long profile.
Its velocity increases.
Suggest reasons why the wetted perimeter of a river will increase in size downstream.
It increases downstream because many tributaries join the main river increasing the amount of water in the river.
Suggest reasons why the rivers wetted perimeter becomes smoother down it long profile.
It becomes smoother because the river has had more time to erode the stoners and pebbles that make up it bed and banks.
Suggest reasons why a river may despot the load that it is carrying.
It may deposit its load when the rivers does not have enough energy to carry the load it is carrying due to a drop in velocity.
What size of load will the river drop first after a reduce in it velocity.
It will deposit the largest load first such as boulders and stones.
When does a river carry out the majority of its erosion.
Most erosion occurs when a river has a very high discharge and velocity usually after a heavy period of rainfall.
Explain why rivers in their lower course have a very high velocity.
They have a very high velocity because the loose little energy over coming friction as there beds and banks are very smooth,
