Water on the Land Flashcards
What is hydraulic action?
Hydraulic action is a type of erosion.
Hydraulic action is the force of the water hitting the bank and bed of the channel.
What is abrasion?
Abrasion is a type of erosion.
Abrasion is when rocks carried in the channel get flung and hit the bank and bed of the river.
What is attrition?
Attrition is a type of erosion.
The rocks carried in the river load scrape each other and overtime bits them break off because they become weakened.
What is solution? (erosion)
Solution is a type of erosion.
Solution is when the certain type of rocks such as limestone, that are soluble, get dissolved in the water.
What are the four types of erosion?
- Hydraulic action
- Abrasion
- Attrition
- Solution
What is transportation?
When the material the river has eroded is transported downstream.
What are the four processes of transportation?
- Traction
- Saltation
- Suspension
- Solution
What is Traction?
Traction is the first process of transportation.
Large boulders get pushed along the river bed because they are too heavy to float.
What is saltation?
Saltation is the second process of transportation.
Saltation is when pebble sized rocks bounce along the river bed by the force of water.
What is suspension?
Suspension is the third process of transportation.
Suspension is when grains of sand and fine materials get carried as the water flows.
What is solution? (transportation)
Solution is the fourth process of transportation.
Particles like chalk and limestone, that are soluble, get dissolved in the water.
What is deposition?
Deposition is when the river drops of the material that is carried in the water.
What type of material is deposited first and why?
Larger pebbles are dropped off first because these are the heaviest and require the most energy to be carried. The smaller the material the further it can be travelled downstream.
When does a river deposit it’s load?
A river will deposit it’s load when there is a fall in water and energy.
What is the long profile of a river?
The long profile of a river is how the rivers height changes downstream; in the upper, middle and lower course.
What is the cross profile of a river?
The cross profile of a river is the shape of the valley.
As you move towards the mouth of the river you should see the cross profile getting wider and less steep.
How does the long profile change between the upper, middle and lower course?
In the upper course the valley is steep and wide. In the middle course the valley is wider, deeper and less steep. And when you move to the lower course the land is generally flat, and the river is widest.
Describe the cross profile of the upper course.
V - shaped valley
Steep sides
Narrow
Shallow channel
Describe the cross profile of the middle course.
Gentle sloping valley sides
Wider and deeper channel
Describe the cross profile of the lower course.
Very wide flat valley
Very wide and deep channel.
What are the human uses of the upper course?
- Quarrying
- Dams for water supply
- Sheep farming
What are the features of a river in the upper course?
- Gorges
- Waterfalls
- Interlocking spurs
What are the human features of the middle course?
- Crops and animals
- Many villages
What are the features of a river in the middle course?
- Meanders
What human features are found in the lower course?
- Fertile plains for farming
- Flat land for towns
- Land use is very urban
What are the features of a river in the lower course?
- Ox bow lakes
- Levees
- Meanders
What is vertical erosion?
Where is it most dominant and what features does it create?
When the river is eroded downward making a v - shaped valley. This is most common in the upper course.
What is lateral erosion?
Where is it most dominant and what features does it create?
Lateral erosion is where the river erodes the banks. This widens the valley and is most common in the middle and lower course.
Explain the formation of waterfalls and gorges.
- Waterfalls form when there is hard rock on top of soft rock.
- The softer rock gets eroded by the falling waters splash back by hydraulic action, the sheer force of the water hitting the soft rock and abrasion, when rocks carried in the falling water get flung at the soft rock and scrape it.
- This undercuts the soft rock so the hard rock is left overhanging.
- A steep drop is created, forming a waterfall.
- The hard rock collapses because it is not supported by the soft rock.
- The hard rock that have collapsed are swirled around at the bottom of the waterfall and erode the soft rock by abrasion, which creates a deeper plunge pool.
- Overtime the waterfall retreats more, creating a gorge.
Explain the formation of a meander.
- Meanders are found in the middle and lower course of a river.
- The flow of the water is fastest on the outside bend so erosion by hydraulic action and abrasion occur here, this creates a river cliff.
- The flow of the water is slowest on the inside bend so the materials from the river are deposited here, creating a slip off slope.
Explain the formation of an oxbow lake.
- Erosion occurs of the outside bend of a meander causing the neck of the meander to get narrower.
- During a flood the neck of the meander will break through the neck.
- This creates a straight channel. Most of the water goes through the new channel as this is the fastest route.
- The slowest flow of water is on the outside of the bend so most material is deposited here, creating land between the strains channel and the meander bend.
- This creates a meander.
What is a flood plain?
- The flood plain of a river is the area of land that can get flooded.
- When a river floods the material is deposited on the floodplain.
- This causes the floodplain to get higher.
- When meanders migrate (Meander migration) they move across the floodplain and makes the floodplain bigger.
- Deposition that occurs on the inside bend of a meander builds up the floodplain.
What is a levee?
A levee is a natural embankment on a river.
Explain how levees are formed.
- The river overflows during a flood so all of the eroded material is deposited over the flood plain.
- The heaviest material is deposited closest to the river whereas the lightest material is deposited further away from the river.
- After repeated flooding the levees are built up, causing the levee to get higher.
What are the physical causes of flooding?
1) Rock type - if a rock is impermeable it won’t absorb the water so the water will run off into the river. On the other hand if a rock is permeable the water can be absorbed into the ground.
2) Relief - If steep slopes surround the river then the water will run off the slopes quicker because the slopes cannot intercept the water so it runs off into the river.
3) Tributaries - When lots of tributaries join a new channel, the water from the tributaries also join the new channel, so there is lots of water in the same area.
4) Rainfall - The more rain that falls the more water that enters the river. Soil also becomes saturated, which encourages surface run off.
5) Snow melt - As temperatures rise the snow melts and the water runs off into the river.
What is the difference between impermeable rocks and permeable rocks?
If a rock is impermeable it won’t absorb the water so the water will run off into the river. On the other hand if a rock is permeable the water can be absorbed into the ground.
What are the human causes of flooding?
1) Urbanisation - In urban areas there is lots of concrete, which is an impermeable rock, so the likelihood of surface run off increases. In addition to this drains take water faster to the river
2) Deforestation - When tree’s are chopped down there is less infiltration so more water reaches the channel. This can also increase soil erosion.
How can different rock types cause flooding?
If a rock is impermeable it won’t absorb the water so the water will run off into the river. On the other hand if a rock is permeable the water can be absorbed into the ground
How can relief cause flooding?
If steep slopes surround the river then the water will run off the slopes quicker because the slopes cannot intercept the water so it runs off into the river.
How can tributaries cause flooding?
When lots of tributaries join a new channel, the water from the tributaries also join the new channel, so there is lots of water in the same area.
How can rainfall cause flooding?
The more rain that falls the more water that enters the river. Soil also becomes saturated, which encourages surface run off.
How can snow melt cause flooding?
As temperatures rise the snow melts and the water runs off into the river.
How can urbanisation cause flooding?
In urban areas there is lots of concrete, which is an impermeable rock, so the likelihood of surface run off increases. In addition to this drains take water faster to the river.
How does deforestation cause flooding?
When tree’s are chopped down there is less infiltration so more water reaches the channel. This can also increase soil erosion.
What is the case study for flooding in a rich country?
- Location
- Date
- River
- Boscastle, Cornwall.
- 16th August 2004.
- Boscastle is at the confluence of the River Valency and the River Jordan.
What are the causes to the Boscastle flood?
- Heavy rainfall (75mm in 2 hours)
- Urbanised area
- Little tree’s
What are the primary effects of the Boscastle flooding?
- No one was killed
- 58 properties were destroyed
- The tourist information centre was destroyed
- Roads and bridges were destroyed
What are the secondary effects of the Boscastle floods?
- 1000 residents are tourists had to sleep in temporary accommodation.
- Loss in tourism
- Damages cost £15 million
What are the immediate responses of the Boscastle floods?
- 100 people were rescued by 7 helicopters
- 1000 residents had to sleep in temporary accommodation
- They cleared the debris e.g cars and trees
Name three long term effects of the Boscastle flood.
- £4.5 million scheme to improve flood defences. (River banks were raised and the channel was made deeper and wider)
- Rebuild houses and shops.
- They had to get tourists back.
What is the case study for flooding in a poor country?
- Location
- Date
- River
- Bangaldesh
- ## July to September 2004
What are the physical causes for the Bangladesh flood?
- 70% of Bangladesh is less than 1 meter above sea level.
- Snow melts in the Himalayas during the summer.
- Three major rivers meet in Bangladesh.
What are the human causes of the Bangladesh floods?
- Rapid population growth had led to increased urbanisation.
- Deforestation has increased surface run off in Nepal.
What are the Primary effects of the Bangladesh flood?
- Rice, vegetables and crops destroyed
- 8.5 million homes destroyed
- 60% of the country was underwater
What are the secondary effects of the Bangladesh flood?
- Over 1 million children were at risk of malnutrition
- 30 million homeless
- 250,000 people had to live in flood shelters
Name two immediate responses to the Bangladesh floods.
- Water aid provided water purification tablets
- Emergency food, medicine, clothing and blankets were provided.
Name two long term responses to the Bangladesh floods.
- Local communities began to rebuild homes
- Flood shelters were built for future flooding
What is hard engineering?
Building artificial structures designed to prevent flooding. This changes and controls the natural processes of a river.
What is soft engineering?
Working with the river system without changing it. E.g planting tree’s.
