Rivers And Water Flashcards
Define discharge.
The volume of water in a river. There is less in the uplands.
What are the four types of erosion?
Hydraulic action, abrasion, attrition and solution.
Explain saltation.
Smaller pebbles and stones are bounced along the river bed, picked up and dropped as the flow of the river changes.High energy.
How does a waterfall form?
A river meets soft rock which is eroded faster than harder rock.
Vertical erosion happens and a step in the river forms.
Abrasion and other forms of erosion causes undercutting.
Hydraulic action causes a plunge pool to form.
The hard rock is undercut and collapses and the water fall retreats up stream.
Explain suspension.
Finer sand silt-sized particles are carried along in the flow of the river. The water looks brown and it is low energy.
Explain attrition.
Eroded rocks get picked up and are smashed against each other. They get smaller and their edges rounder.
Why might deposition occur in a river?
It happens when the velocity of the river slows down. This can happen because the volume of water in the river falls
The amount of eroded material in the water increases.
The water is shallower
The river reaches its mouth.
Explain traction.
Large boulders and stones are rolled along the river bed. High energy.
Explain lateral erosion.
This widens the river and channel. Dominant in the middle and lower courses.
Why is the water slower on the inside bend of a menader?
The channel is shallower and there is more friction.
What are the negatives of flood warnings?
It doesn’t stop a flood. Living in a place that floods a lot will increase insurance prices. People may not hear the warnings.
What are the four types of transportation?
Traction, suspension, saltation and solution.
Explain vertical erosion.
This causes the channel and valley to deepen making it V shaped. Happens mostly in the upper course.
Where is is the fastest currant?
On the outside of the river.
What are the two land forms you can find in meander?
A river cliff on the outside bend where is is erosion and a slip off slop on the inside bends where deposition takes place. It is a deposit of sand and smaller particles.
Explain solution.
Minerals like limestone and chalk are dissolved in the water and carried along. Low energy.
Where are meanders mostly found?
In the middle course where there is more lateral erosion.
How does a levee form?
Often serval meters higher than the flood plain.
Happens in the lower course where a lot of eroded material is
During a flood, eroded material is deposited on the edges of a river bank. Heavy material is closer to the river as it gets dropped first.
What is discharge measured in?
Cumecs. Square meters per second.
What were the responses to the flooding of Bangladesh?
Boats and emergency services sent out. Repair to sewage systems. New laws to stop deforestation. 7 dams being built. 5000 flood shelters being built to hold the population.
What is surface run off?
When water flows over land to get to a river.
What type of erosion happens on the outside of a meander?
Lateral erosion in the form of abrasion and hydraulic action.
What can affect peak discharge and the lag time?
Lots of rain is a short space of time means more runoff and a smaller lagtime.
Hot, dry or freezing conditions can make the ground hard,increasing runoff and decreasing lagtimes.
The rock type. Permeable or impermeable.
Previous weather conditions. Is the ground saturated?
Land use. In an urban area there is lots of impermeable concrete.
What are the negatives of preparation?
Doesn’t guarantee safety from a flood. Expensive to modify buildings. It could give people a false sense of security.
Explain Chanel straightening and the positives.
Meanders are cut out by building artificial straight channels.
Water moves through the area quicker as it doesn’t have to travel as far, reducing the risk of flooding.
Explain flood warnings.
People are warned about possible floods by TV, radio, newspapers and the internet. The impact of flooding is reduced as people can move things upstairs, put up sandbags and evacuate.
What is the lag time?
The time between the peak flow and the peak dischage.
What is a meander?
They are bends in the river’s course.