Fichas
River Landscapes & Processes
Fichas del conjunto (48)
- 1What is the drainage basin?An area of land drained by a river and its tributaries.
- 2What is the source of the river?The start of a river.
- 3What is the mouth of the river?Where a river meets the sea
- 4What is a tributary?A stream or small river that joins a larger river.
- 5What is the watershed?The boundary of a river basin. Usually highland.
- 6What is a confluence?The point where two rivers meet.
- 7What happens to the channel width and depth downstream?They increase
- 8What happens to velocity downstream?It increases
- 9What happens to discharge downstream?It increases
- 10What happens to gradient downstream?It decreases
- 11What river have we looked at to see changes characteristics downstream?River Dee
- 12Give examples of the impact of the UK’s weather and climate on river processes (e.g. erosion rates)Erosion rate will be greater with greater discharge as the river flows faster and so has more energy to erode. Therefore, rivers in wetter climates will erode more material than those in dryer climates, widening and deepening river valleys and increasing the amount of eroded sediment.
When droughts occur rivers have less water and, therefore, have less power to erode the banks and beds. In addition to this, rainwater cannot easily infiltrate hard dry soil, and so it flows to the river as surface run-off increasing the chance of a flood. - 13Give examples of the impact of the UK’s weather and climate on river landforms and landscapesLevees are depositional landforms that form when the river is in flood. Therefore, greater rainfall and so greater discharge, can result in larger levees.
The human river landscape, such as river defences, are in need of repair more regularly due to the increasing regularity of storms in the UK. Many urban areas have had to install river defences, causing a change to the river landscape on the floodplain. - 14Give 2 river landforms found in the upper course?Interlocking spurs and v shaped valleys
- 15Explain their formation with reference to geology and erosion processes.Rivers do not have a lot of energy near the source due to having such small discharge.
They erode vertically (by hydraulic action and abrasion) resulting in v-shaped valleys.
However, they do not have the power to laterally erode the hard rock of the valley sides (the spurs).
As a result they flow around the spurs, resulting in the spurs from each side of the valley interlocking. - 16Give 3 river landforms found in the middle/lower course?Meanders, oxbow lakes and point bars
- 17Explain their formation with reference to depositional and erosion processes.Meanders n point bars: In middle stages river has more discharge, so has more energy to erode laterally, forming meanders. Fastest flow occurs on outside bend (where is deeper so less friction). Faster flow so more erosion by hydraulic action and abrasion. Erosion leaves steep slope called river cliff. Slower flow is found in the shallower inside bend as effect of friction is greater. Slower flow has less energy n so deposition takes place, creating point bar (slip-off slope). Underwater current takes some of eroded material from river cliff across river n deposits it on point bar. Bends migrate over time.
Oxbow lakes: Both sides of neck of meander erode over time by processes like hydraulic action. Erosion results in neck becoming more narrow. In flood, discharge increases so velocity increases as friction with beds and banks is reduced. So, river has more energy, increasing the rate of erosion. As a result, river breaks through meander, creating straight channel. Is shallow at sides so slowest so river drops load at sides cos no energy. Cuts meander off, making oxbow lake. - 18Give 2 river landforms found in the lower course?Floodplains and river cliffs
- 19Explain their formation with reference to depositional and/or erosion processes.Floodplains: A floodplain is the low, flat area of land on either side of a river.
Migrating meanders can laterally erode the valley sides by processes such as hydraulic action and abrasion, to create a wide, flat valley bottom.
In addition to this, flooding of the river can deposit silt or alluvium. This flattens the landscape by covering it.
he flat valley created by both erosion and deposition, is surrounded on both sides by low hills called bluffs.
River cliffs: These occur on river banks on the outside of meanders in the middle and lower stages of a river.The fastest flow is on the outside of a meander due to deeper water and so less friction. The faster flow has more energy to erode the outside bank by processes such as hydraulic action and abrasion. This causes material to break off. Eventually the bank collapses leaving a steep river cliff. - 20Give an example of how urbanisation has affected rivers, such as the River Dee.The building of roads and drains means that water can reach the river more quickly after rainfall. This means that the river is much more likely to flood because of the disruption in the balance of water flow to the river.
- 21Give an example of how Agriculture has affected rivers, such as the River Dee.Farmers also drain land close to rivers with artificial drainage ditches that allow water to flow to the rivers of the area more quickly. This can cause flooding as more water enters the channel at a given time.
- 22Give an example of how industry has affected rivers, such as the River Dee.In the summer the River Dee’s natural flow does not provide enough water to meet the demand for industry and people. Growing demand in the 1960s led to a number of reservoirs being built to store water during the winter months. These reservoirs help control the river’s flow, and can reduce its discharge.
- 23What is the difference between physical and human causes of flooding?
- 24Explain how heavy rainfall increases the risk of flooding.If there has been rain for a number of days then the ground becomes saturated. This then increases surface run-off so more water flows straight into the rivers causing them to flood.
- 25Explain how impermeable rock increases the risk of flooding.Rainwater cannot soak through impermeable rock so it will flow straight to the river as surface run-off, so the river will receive more water at one time, increasing the chance of flooding.
- 26Explain how an increase in temperature after snowfall increases the risk of flooding.This will cause the snow to melt, resulting in a rapid increase in the amount of water entering the river, increasing the flood risk.
- 27Explain how a long period of dry, hot weather increases the risk of flooding.This will cause the soil to become very hard so water cannot soak through it. As a result rainwater will run straight to the river as surface run-off, increasing the amount of water at one time, and so increasing the flood risk.
- 28Explain how river beds that have become silted up increase the risk of flooding.This makes the channel smaller and so there’s less room for water, which increases the chances of a flood.
- 29Explain how steep valley sides increase the risk of flooding.Rainwater quickly runs down the steep slopes, resulting in more water entering the river at one time, so increasing the chance of a flood.
- 30Explain how deforestation increases the risk of flooding.There is less interception of rainwater by the leaves, and less water is soaked up by roots. Therefore, water reaches the river more quickly increasing the chance of it flooding.
- 31Explain how building on the flood plain (urbanisation) increases the risk of flooding.Water is unable to soak through tarmac and so it runs straight to the river as surface run-off. Also, water that goes down drains runs very quickly to the river. This means the river receives more water at one go, increasing the chance of flooding.
- 32Explain how farmers ploughing up and down slopes instead of around the hillside can increase the flood risk.The channels created by the plough allow rainwater to travel faster to the river, so the river receives more water at one time, increasing the risk of flooding.
- 33Explain how a bursting dam can increase the risk of flooding.Excess water will enter the river channel, causing the flooding of a large area.
- 34Give the three main reasons for why there is an increasing flood risk in the UK.An increasing population, which results in changes to land use.
Changes to land-use – e.g. more urban surfaces that are impermeable.
Changes to weather patterns, particularly linked to climate change. For example, in December 2013 and January 2014, the UK experienced the wettest two-month period of rainfall since 1910. The River Thames recorded its highest discharge for over 60 years. - 35What is a storm hydrograph?A hydrograph which shows how a river responds to a storm event
- 36On a storm hydrograph, what does the rising limb represent?The rapid rise in water after a period of heavy rain
- 37What is the lag time?The difference between the time of the heaviest rainfall and the point in which the river contains the largest amount of water
- 38What does the falling limb represent?The reduction in the amount of rainfall reaching the channel
- 39Give examples of how floods can affect people and the environment.Homes can be destroyed, resulting in large insurance claims and money having to be spent on temporary accommodation.
Crops can be destroyed resulting in a lack of food.
Damage to properties and their sewage pipes can contaminate rivers and the sea, which can be harmful to wildlife.
Large areas of farmland can be covered, which can destroy some wildlife habitat. - 40Give some located examples of major floods in the UK and their specific effects.North Wales, Cumbria and South West England – 2012. Rained persistently from April to November. The ground became saturated , causing huge amounts of surface run-off and flooding.
9 people died (social)
8000 homes were flooded (social)
£600 million of crops were ruined. (economic)
Boscastle, 16th August 2004. A month’s worth of rain fell in one day, leaving the village in ruins.
100 homes and businesses were destroyed. (social and economic).
75 cars were washed out to sea. (social)
Tourist industry was significantly affected as hotels and tourist services were destroyed. (economic) - 41Give examples of hard engineering techniques and their advantages and disadvantages.Channelisation(A river channel may be widened or deepened allowing it to carry more water. It can also be straightened so that the water can travel faster along the course): Advantages - Effectively protects the immediate area from flooding because water is moved away quickly.
A deeper channel can hold more water and so is less likely to flood.
Disadvantages - Water taken downstream may put other places at risk of flooding.
Unnatural and visually intrusive.
Dams and Reservoirs (These are often built along the course of the river in order to control the amount of discharge; water is held back by the dam and released in a controlled way): Advantages - By holding water back discharge will be reduced downstream, reducing the chance of a flood.
Long lasting.
Disadvantages - Sediment is often trapped behind the wall of the dam, leading to erosion further downstream.
Settlements and agricultural land may be lost when the river valley is flooded to form a reservoir. - 42Give examples of soft engineering techniques and their advantages and disadvantages.Floodplain Zoning (Local authorities and the national government introduce policies to control urban development close to or on the floodplain): Advantages - It’s sustainable because it reduces the impact of flooding and building damage is limited.
No building on the floodplain means less surface runoff, so rainwater should take longer to reach the river, reducing the flood risk.
Disadvantages - Some people are against restricting urban development in areas where there is a housing shortage .
Enforcing planning regulations and controls may be harder in LICs.
River Restoration (Restoring the river’s natural course): Advantages - Restoring rivers to a more natural course by taking away embankments aims to slow them down, for example by restoring meanders.
Natural rivers are more attractive and create natural habitats for wildlife.
Disadvantages - Some flood banks are often still needed, and like floodplain retention, changes in land-use may bring some disadvantages - 43Give examples of how land-use can be managed to reduce the risk of flooding.Managing farmland can reduce runoff, for example, by avoiding overgrazing by animals (as this can increasing runoff), and by ploughing across slopes rather than downhill to reduce the speed it takes for runoff to reach the river.
Afforestation helps reduce the flood risk because woodland intercepts rainfall, and tree roots encourage infiltration of water. This means its takes longer for rainfall to reach the river and so discharge shouldn’t increase as much, thus reducing the flood risk. - 44What are the three warning levels used by the Environment Agency?Flood warning (flood is expected, immediate action required), flood alert (flooding is possible,be prepared) and severe flood warning (severe flooding, danger to life)
- 45What does the Environment Agency use to provide an up-to-date overview of potential areas at risk?Flood warning feeds, a live flood warning map and a three-day flood risk forecast.
- 46By what means does the Environment Agency, the local government and other organisations educate the population about the hazards of living in flood prone areas?They use television, the internet , leaflets, helplines and training exercises to make people aware of what they should do before, during and after a flood.
- 47Give examples of the advice that the Environment Agency gives to home owners to help reduce the impacts of flooding.Replace wooden window frames and doors with synthetic ones.
Raise the height of electrical sockets to 1.5m above the ground floor level so the flood water doesn’t interfere with the electricity supply.
Lay tiles on the ground floor and use rugs instead of carpets. This reduce the amount of damage done by flood water, so reducing the effects.
Position any main parts of a heating or ventilation system, such as boilers, upstairs, so they are away from the flood risk. - 48Give examples of how physical and human processes have impacted on the River Dee landscapePhysical: The River Dee flows easterly, eroding the heavily glaciated upland landscape formed of igneous and metamorphic rocks.
Near Chester the river meanders across a wide floodplain, eroding softer sedimentary rocks and depositing sediment.
Human:1732-1736 – channelisation of 8km improved navigation, increasing discharge and velocity and creating an artificial (man-made) landscape.
If sea levels rise by 1m by the year 2100, coastal landscapes will replace salt-and freshwater marsh landscapes.
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- Year 9 (Physical Geography) Geography Fichas sobre River Landscapes & Processes , creado por Jamie Etu-Menson el 30/08/2019.
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- Jamie Etu-Menson
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