Water on the Land Flashcards
Can you explain the process of hydraulic action?
The power of the volume of water moving in the river.
Can you explain the process of abrasion?
Occurs when larger load carried by the river hits the bed and banks, causing bits to break off.
Can you explain the process of attrition?
Load carried by the river knocks into other parts of the load, so bits break off and make the material smaller.
Can you explain the process of solution?
The dissolving of certain types of rock such as chalk and limestone by rainwater.
How do rivers tend to erode?
Vertical and lateral erosion.
Can you explain how the type of erosion changes as a river gets further down its course?
Vertical erosion becomes less important and lateral erosion takes over.
Can you explain the process of traction?
The rolling along of the largest rocks and boulders.
Can you explain the process of saltation?
The bouncing movement of small stones and grains of sand along the river bed.
Can you explain the process of suspension?
Small material carried within the river.
What is deposition?
Where the river dumps or leaves behind material that it has been carrying.
When is the largest material deposited?
In the upper course because it is the heaviest to carry.
When is the smaller material deposited?
Much further downstream because it is smaller so can be transported further.
When does the river drop some of its load?
When there is a fall in the speed of the water or the amount of water is less.
When is the speed of the water or the amount of water less?
When the gradient changes at the foot of a mountain or when a river enters a lake or sea.
What does a long profile show?
How the river changes its height along its course.
What does a cross profile show?
How the river’s valley changes shape downstream.
What are the characteristics of the upper course? 7
Mention: channel shape / which erosion / which erosion process / what transportation process / what is deposited / load size / valley shape
- shallow, narrow channel
- vertical erosion
- hydraulic action, abrasion and attrition
- some traction and saltation at high flow
- deposition of large material
- large load
- v-shaped valley
What are the characteristics of the middle course? 7
Mention: channel shape / which erosion / which erosion process / what transportation process / what is deposited / load size / valley shape
- wider, deeper channel
- some vertical erosion; lateral erosion more important
- hydraulic action less important
- suspension main transportation; saltation and traction still present
- deposition more obvious
- load size reduced
- v/u shaped valley
What are the characteristics of the lower course? 7
Mention: channel shape / which erosion / which erosion process / what transportation process / what is deposited / load size / valley shape
- widest, deepest channel
- less erosion; only a little lateral
- all erosion much less important
- suspension dominant
- deposition of fine material
- large amount of load, size now very small
- u-shaped valley
What landforms are a result of erosion? 2
- waterfalls
* gorges
What landforms are a result of erosion and deposition? 2
- meanders
* oxbow lakes
What landforms are a result of deposition? 2
- levees
* floodplains
How are waterfalls formed? 6
- hard rock (granite) overlies soft rock (sandstone)
- softer rock is eroded away faster than hard rock
- plunge pool is created
- plunge pool is deepened due to potholing which swirls around and rubs the bed and the banks
- an overhang forms as the softer rock is eroded further
- eventually the overhang collapses as it is unsupported
How is a gorge formed?
When the hard rock collapses because it is unsupported and the waterfall moves upstream.
How is a meander formed?
As the river erodes laterally, it forms large bends, and then horseshoe-like loops.
How is an oxbow lake formed? 4
- erosion causes a meander to narrow
- meander will eventually break off
- river now follows a straight path
- meander is cut and the river seals off the bend
How is a levee and floodplain formed? 2
- involve repeated flooding and the build-up of material during the period of flood
- under normal conditions, the river is contained within its banks and so no sediment is available to form them
What is precipitation?
Any source of moisture reaching the ground.
What is interception?
Water being prevented from reaching the ground by trees or grass.
What is surface storage?
Water held on the ground surface.
What is infiltration?
Water sinking into soil/rock from the ground surface.
What is soil moisture?
Water held in the soil layer.
What is percolation?
Water seeping deeper below the surface.
What is groundwater?
Water stored in the rock.
What is transpiration?
Water lost through pores in vegetation.
What is evaporation?
Water lost from ground/vegetation surface.
What is surface run-off (overland flow)?
Water flowing on top of the ground.
What is throughflow?
Water flowing through the soil layer parallel to the surface.
What is groundwater flow?
Water flowing through the rock layer parallel to the surface.
What is a water table?
Current upper level of saturated rock/soil where no more water can be absorbed.
How does rainfall affect river discharge? 2
- a lot of rain causes high river levels
* less rain results in lower river levels
What is the explanation for how rainfall affects river discharge? 2
- high amounts of rain saturate the soil and underlying rock
- in the case of drizzle, there is time for water to infiltrate the soil and underlying rock, freeing space for more rain
What factors affect river discharge? 6
Weather: • rainfall • temperature • previous weather conditions Physical • relief • rock type Other: • human land use
Can you explain how temperature affects the loss of water from the drainage basin?
When temperatures are higher, there is greater water loss via evaporation and transpiration, so river levels go down.
Can you explain how previous wether conditions affect river discharge?
If it has been dry, it will take longer for the water to reach the river and the amount will be less than if there had been a number of wet days.
What does relief affect?
The rate at which water runs off the land surface and into rivers.
What do steep slopes encourage?
Fast run-off as the water spills rapidly downwards due to gravity.
What do gentle slopes allow time for?
Infiltration to occur.
What is rock type important for?
Determining how much water infiltrates and how much stays on the surface.
What happens in areas where more water is on the surface?
The discharge of the river is higher as it reaches the river fastest.
What are the most important land-use changes with regard to influencing river discharge? 2
- deforestation
* urbanisation
What happens if trees are removed affecting discharge?
Water reaches the surface faster and the trees do not extract water from the ground.
What happens when towns are expanded affecting discharge?
They create an impermeable surface. This is made worse by building drains to take the water away from buildings quickly - and equally quickly into rivers.
What physical factors cause flooding?
- prolonged rainfall
- heavy rain
- snowmelt
- steep relief
How do people unintentionally increase the likelihood and severity of floods?
As a result of deforestation and construction work.
What is hard engineering?
This strategy involves the use of technology in order to control rivers.
What is soft engineering?
This option tries to work within the constraints of the natural river system.
How do dams and reservoirs exert a huge degree of control over a river?
Natural flow of water is prevented. Water fills the area behind it and is released or held depending on circumstances such as current and expected rainfall.
Can you explain how straightening meanders can manage rivers?
The river is made to follow a shorter, straight section and abandon its natural meandering course.
What do flood warnings help people to do? 5
Allows people time to • take possessions • turn off gas • turn of water and electricity • gather important papers • take some basic precautions
What does floodplain zoning do?
Takes into account frequency and severity of flooding.
Why is there an increase in demand for water in the UK? 3
- increased number of households
- increased population
- more affluent lifestyle
How is the demand for water met in a sustainable way?
- focus on local schemes
* encouraging conservation
Can you explain how encouraging conservation decreases the demand for water? 5
- houses are designed with better water efficiency
- devices are fitted to toilets to reduce water usage
- rainwater collected
- bath water recycled
- people take more showers than baths
Why is there a need for water transfer?
To transfer it from areas of surplus to areas of deficit.
What were the causes of the Queensland floods? 6
- Queensland’s wettest December on record-prolonged rain
- rains peaked in January 2011
- steady rise in river levels over a period of time
- La Niña - warm water trapped, generating heavy rain clads
- warmer ocean temperatures due to global warming
- Toowoomba had 36 hours of constant rain amounting to 160mm
What were the effects of the flooding in Queensland? 6
- 35 people died in flood related incidents
- Brisbane = 25,000 were flooded
- 100,000 homes had electricity cut off (precaution)
- mud and debris all over city
- GDP estimated to be reduced by A$30 billion
- area larger than France + Germany flooded
What were the responses to the Queensland floods? 6
- 9th January = appeal on national temperature raised A$10 million
- rally for relief attended by 15,000 people on 16th January
- Queensland Reconstruction Authority formed for rebuilding
- government promised to raise A$5.6 billion
- no international aid
- Australian Defence Force
What were the causes to the Bangladesh floods? 6
- lies in belt of onshore winds - up to 1m can fall in single monsoon
- in path of tropical cyclones
- close to sea level
- growing population
- soil erosion - goes into river, increases capacity
- houses built by poor near water - restricts movement
What were the effects of the Bangladesh floods? 7
- 670,000 hectares destroyed
- killed more than 1,000 people
- 30 million people displaced
- 50 million living below poverty line
- 17 million living in slums
- cycle of poverty
- thousands migrating to Dhaka
What were the responses to the Bangladesh floods? 5
- Oxfam distribute emergency supplies
- west flood embankment built in Dhaka
- new channels and underground drains built but need maintenance
- mud road and embankment built in rural area
- adopt farming techniques
