Rivers Flashcards
Describe the upper course of a river
The river starts as many tributaries, which arenarrow and V-shaped.Each tributary doesn’t carry a lot of water, but combined the tributaries all fill up the river channel further down. The sides of the tributaries tend to be like a valley,with a large gradient either side so water can run into the tributary.
Describe the middle course of a river
The tributaries merge together to form a channel, which is rounder in shape and deeper. The area around the river channel isflat and low-lying,which is the floodplain if the river needs to flood
Describe the lower course of the river
It carries thelargest volume of water in a very wide and very deep channel. There are ridges either side of the river banks called Levees. The size of the valley has increased, so it is even wider and flatter than the middle course
What do storm hydrographs represent
Storm hydrographs represent the variation in the river’s discharge (the volume of water passing through the river channel at a specific point)within a short period.
How does Topography increase the risk of river flooding
The shape of the land will determine how quickly rain water flows into the river.Steep hills withhigh gradients are more likely to have flash floods than gradual gradients.
How does Geology increase the risk of river flooding
If the area has many impermeable rocks,the rain water can’t run into the soil. Instead, the rain water runs straight into the river, increasing the risk of flash flooding
How does rain increase the risk of river flooding
If there is a storm and a large amount of rain falls in a short amount of time, this can cause the river to flood
What are the physical factors which increase the risk of river flooding
Rain
Geology
Topography
How does Littering increase the risk of river flooding
If the river becomes filled with rubbish and debris, the channels size will decrease. This means the river can carry less water.
How does Deforestation increase the risk of river flooding
Trees intercept rain and so it takes longer for the rain to travel through the leaves and into the river. Cutting trees shortens the time down
How does urbanisation increase the risk of flooding in a river
Increases the amount of impermeable surfaces, which decreases the time taken for water to flow into the river
What are the human factors which increase the risk of flooding
Urbanisation
Deforestation
Littering
How are Mudflats and saltmarshes created
When both the tide from the estuary and the water flow from behind the river disrupt the rivers flow. There is a large amount of deposition. which creates mudflats and salt marshes
What are river estuaries
Located at the mouth of the river, it is where the river meets the sea
What is a leeve
They are river banks in the lower course of the river. they are higher than the river itself. They are a natural way of stopping river floodings
How do meanders form
Water travels faster on the outside of the bend which causes lateral erosion
On the opposite side the water travels slowly and changes direction sharply until the water loses energy and deposit sediment
What are Interlocking spurs
Interlocking spurs are found in the upper course of the river where the water doesn’t have a lot of energy so it isn’t very powerful
the low energy means the water isn’t strong enough to erode resistant rocks, instead the river rerouting curls around them
What is Solution in rivers
Chemicals dissolved in the river water
What is Suspension in rivers
Particles and small rocks are light enough to float within water
What is Saltation in rivers
Pebbles and small rocks are to heavy to be suspended , bounce along the river channel
What is Traction in rivers
Large rocks are rolled along the river bed
What is deposition in rivers
Deposition is the dropping of the rivers load when the water in a river decreases in speed
If the River Travels slower, the water has less energy and can carry less material
Which river land forms are found in the upper course of a river
-Waterfalls
-Interlocking spurs
-V shaped valley
Which river land forms are found in the middle course of a river
-Gorges
-Meanders
Which river land forms are found in the lower course of a river
-Flood plains
-Ox bow lake
-River estuary
How do water falls form
In an area where a river flows
over an area of hard rock and
soft rock, the soft rock erodes
more quickly.
The soft rock erodes away from the hard rock over time creating a step
The soft rock continues to erode undercutting the hard rock The hard rock is left suspended in the air as an overhang
Due to the force of gravity the unsupported overhang collapses on the broken up rocks fall into the plunge pool which acts as tools for erosion and further deep into the plunge pool
Erosion continues to undercut underneath the hard rock creating overhang again further upstream
The continual process of the overhang collapsing causes the waterfall to retreat upstream
What are gorges
Gorgeous form from water falls as the waterfall retreats upstream it leaves behind A steep valley carved into the rock with a river running along the base
What are the two ways a storm hydrograph can be described as
flashy
subdued
How can you tell with a storm hydrograph when there was a flash flooding
-Short lag time
-high maximum discharge
How can you tell with a storm hydrograph when there was a subdued flooding
Longer lag time
Lower maximum discharge
What are the soft engineering methods to reduce river flooding
River channel restoration
Wetlands
What are the advantages and disadvantages of River channel resortation
+
Natural resources are used rather than heavily polluting ones
The natural environment benefits
~
Land will still flood, but often they are parks
What are the advantages and disadvantages of Wetlands
+
Wet lands store river water and can flood when needed, with no damage to houses
~
takes a long time for wet land to grow
What are the Hard engineering methods to reduce river flooding
Dams
Floodwalls
What are the advantages and disadvantages of Dams
+
can control the amount of water which passes through
~
Very expensive
What are the advantages and disadvantages of Flood walls
+
Protects valuable property on the river front.
~
Looks unnatural and destroys habitats along the bank
What were the impacts of the Sheffield river flooding
-1,200 homes were flooded
-1,000 businesses were affected
-13,000 people had no power for two days.
