Water on the land What you should know and links to revision material CUE 1: You need to be able to identify and explain the processes of erosion hydraulic action, abrasion, attrition and solution. CUE 2: You must understand the processes of lateral and vertical erosion. CUE 3: You must identify and explain the processes of transportation traction, saltation, suspension and solution. CUE 4: You need to understand deposition and the reasons it takes place. CUE 5: You need to recognise the long profile of a river and the changes that occur in the upper, middle and lower course of the river. CUE 6: You need to recognise and be able to sketch landforms resulting from erosion waterfalls and gorges. CUE 7: You need to recognise and be able to sketch landforms resulting from erosion and deposition meanders and oxbow lakes. CUE 8: You need to recognise and be able to sketch landforms resulting from deposition levees and floodplains. CUE 9: You need to describe and explain factors affecting river discharge (flow) - amount and type of rainfall e.g. Monsoon / storm event, temperature, previous weather conditions, relief (shape of the land and river profile), rock type (permeable / impermeable) and land use. CUE 10: You need to describe, explain and categorise the causes of flooding. Physical prolonged rain, heavy rain, snowmelt and relief. Human deforestation, building construction. CUE 11: You must be able to describe the location of flood events in the UK in the last 20 years and comment on the increased frequency of these events. CUE 12: You need to be able to name and describe a case study of flooding in both a LDC and MDC and explain the responses to this event. CUE 13: You need to be able to describe flood management strategies. Hard engineering Dams, reservoirs and channel straightening. Soft engineering Flood warning, preparation, floodplain zoning, allowing flooding and the costs and benefits of these solutions.
CUE 14: You need to be able explain the UKs increasing demand for water and the areas of the country with a deficit (lack of) and surplus. You should know about schemes and the need to transfer water to and from these regions. CUE 15: You need to be able to describe a case study of a dam or reservoir and successfully discuss the social, economic and environmental issues. These issues should be linked to future sustainability of our water supply. CUE 1: You need to be able to identify and explain the processes of erosion hydraulic action, abrasion, attrition and solution. Hydraulic Action This process involves the force of water against the bed and banks. Abrasion This is the process by which the bed and banks are worn down by the river s load. The river throws these particles against the bed and banks, sometimes at high velocity. Attrition Material (the load) carried by the river bump into each other and so are smoothed and broken down into smaller particles. Solution This is the chemical action of river water. The acids in the water slowly dissolve the bed and the banks. 1. Explain how a river erodes (3Mks) June 2011 2. Describe one process of river erosion (2Mks) June 2010 CUE 2: You must understand the processes of lateral and vertical erosion. A rivers discharge is low in the upper course, giving the river only enough energy to erode downward. This is called vertical erosion. As the course of a river approaches its middle stages it flows over flatter land. Lateral erosion dominates as the river swings in large bends known as meanders. Meanders constantly change their shape and position. Water is pushed to the outer bend. This reduces friction with the bed and banks. So the river has more energy for transporting material which can erode the outside bank via abrasion. Vertical erosion Lateral erosion
1. Draw a cross section to show how the inside bend of a meander is different from the outside of bend of a meander (4Mks) June 2011 (Tough one, see how you do. If you struggle attempt this after cue 7) 2. Produce a diagram to show the difference between vertical & lateral erosion (2 marks) CUE 3: You must identify and explain the processes of transportation saltation, suspension and solution. traction, Traction Boulders and pebbles are rolled along the river bed at times of high discharge. Saltation Sand sized particles are bounced along the river bed by the flow of water. Suspension Fine clay and sand particles are carried along within the water even at low discharges. Solution Some minerals dissolve in water such as calcium carbonate. This requires very little energy. 1. Describe how a river transports its load (3Mks) June 2012 2. Produce a labelled diagram to show how a river transports material (4 marks) CUE 4: You need to understand deposition and the reasons it takes place. Rivers need to be flowing to pick up and transport material (load). The faster the flow the more energy they have and so can move more load. The opposite is also true. When a river slows its loses energy and with it the potential to transport material. Heavier material will be deposited first. 1. When does a river deposit material? (2 marks) CUE 5: You need to recognise the long profile of a river and the changes that occur in the upper, middle and lower course of the river.
The relief changes from steep to gently sloping. The river valley changes from V shaped valley to floodplain. The speed of the river goes from fast to slow. The processes change from mostly erosion processes in the upper course to deposition processes in the lower course. The channel changes from shallow to deep. The size of meanders increases as you move downstream through the profile. 1. Describe how a river changes between its source and its mouth (3 marks) 2. Describe the long profile of a river and how it changes (3 marks) CUE 6: You need to recognise and be able to sketch landforms resulting from erosion waterfalls and gorges. You need to be able to explain how a waterfall and recessional gorge form. In an area where hard rock is found above softer rock, the softer (less resistant rock) will erode more quickly. Over time this will mean that the harder (more resistant rock) above becomes undercut. This process of undercutting creates an overhang of resistant rock. The process continues until the hard rock overhang is unsupported and eventually collapses. The debris from the overhang will swirl around at the base of the waterfall, through the processes of abrasion and hydraulic action an over deepened pool known as a plunge pool is created. The debris will be broken up and then transported downstream. The process of erosion continues and the cycle repeats. The cycle means that the waterfall moves backwards (upstream), as the waterfall retreats upstream it leaves in front of it a steep sided recessional gorge. 1. Produce a labelled diagram to show the features of a waterfall. (4 marks) 2. Produce an annotated diagram to explain the formation of a waterfall and recessional gorge (6 marks) 3. Explain the formation of a waterfall and recessional gorge (8 marks)
CUE 7: You need to recognise and be able to sketch landforms resulting from erosion and deposition meanders and oxbow lakes. You need to be able to explain how the features of a river bend form and how an Ox-Bow lake forms. Meanders: A meander is a bend in a river. On the outside of a river bend the channel is deep as the water is fast flowing and erosive. The banks erode due to hydraulic action and abrasion. A feature known as a river cliff forms on the outside of a river bend. On the inside of a river bend the channel is shallow as the water has a slow flow and therefore deposits material. A feature known as a river beach or a slip-off-slope is created. Oxbow Lakes Lateral EROSION at two adjacent meanders will cause the channel to move across the land over time. The space in between the two meanders reduced as the neck of land is eroded. Eventually the river breaks through the space between the meanders, perhaps during a flood event. DEPOSITION will eventually create a build up of material that close the neck once more, leaving behind an oxbow lake.
1. Draw a cross section to show how the inside bend of a meander is different from the outside of bend of a meander.(4mks) June 2011 2. Produce an annotated diagram to explain the formation of the features found on a river bend (6 marks) 3. Explain how the features found on a river bend are formed. (6 marks) 4. Produce a series of annotated diagrams to explain the formation of Ox-Bow lakes (6 marks) CUE 8: You need to recognise and be able to sketch landforms resulting from deposition levees and floodplains. Floodplains and leveés are formed by deposition in times of river flood. The river s load is composed of different sized particles. When a river floods it deposits the heaviest of these particles first. The larger particles, often pebble-sized, form the leveés. The sands, silts and clays are similarly sorted with the sands being deposited next, then the silts and finally the lightest clays. Every time the river floods deposition builds up the floodplain. 1. Explain the formation of a floodplain (4Mks) June 2012 (Note there are NO command words to draw a diagram but you could include one) CUE 9: You need to describe and explain factors affecting river discharge (flow) - amount and type of rainfall e.g. Monsoon / storm event, temperature, previous weather conditions, relief (shape of the land and river profile), rock type (permeable / impermeable) and land use. River discharge is the volume of water passing a certain point in the river. The discharge is affected by a number of factors, some human and some natural
Monsoon weather is prolonged seasonal rainfall. Land becomes saturated and river levels steadily rise. Lowland areas such as the flood plain are prone to flooding during the monsoon season. Storm events can create flash floods. This is where the shear volume of water entering the channel is too high for the river to effectively drain away. Temperature can impact on the discharge of a river. In sub-zero conditions water is effectively locked in the soil and its journey to the river is slowed or stopped. Conversely, if frozen land or lying snow thaws quickly it can create a huge input to the river system. This again can trigger the water level to rise or for flooding to occur. Previous weather can impact the effects of heavy rainfall on the channel. Drought can bake the land so dry that surface run-off is increased, increasing the volume of water entering the river channel. Prolonged rain in previous days can soak the surrounding land to saturation point. This also increases surface run-off and flood risk. The shape of the surrounding land (Relief) impacts on flood risk. Refer back to the long profile diagram. V shaped valleys contain water whilst floodplains allow water to travel great distances once it has overtopped its channel. Relief affects the rates of surface run-off and the rivers speed and ability to drain water away effectively. Permeable / impermeable rock type is a factor in flooding because it impacts on the surrounding landscapes ability to sold and store water. Permeable rock allows percolation to occur and can slow waters progress to the river as some water travels vertically. Impermeable rock does not allow vertical movement and increases through flow in the soil above. The soil will reach saturation point quicker and surface run-off will occur. 1. Explain the factors affecting river discharge (6Mks) June 2011 2. Explain how snowmelt can cause a river to flood (3Mks) June 2011 (F) CUE 10: You need to describe, explain and categorise the causes of flooding. Physical prolonged rain, heavy rain, snowmelt and relief. Human deforestation, building construction. For this LDC example below: Bangladesh 1) Write a title 2) Draw a table 3) List human factors 4) List physical factors (Take the details from the diagram below)
Bangladesh Effects -Floods covered half of Bangladesh as the country is low flat land. -Millions were made homeless. (8.5 in 2004) - 760 killed (in 2004) - Food supply disrupted. Rice contaminated with silt and fishing boats damaged. - Infrastructure damaged making travel difficult. Bangladesh Responses - Emergency International Aid to support the country (Food, clean water, shelter, medicines). Refer to a charity such as the Red Cross and an MEDC government pledging support such as the UK. - Longer Term Responses involved the development of a dam network supported by the World Bank, however this scheme remains only partially completed. (This would not be the case in an MEDC) - Longer term soft management strategies are afforestation and the education of local people on the importance of sustainably managing woodland. Flooding in more developed countries can happen for a variety of reasons, such as 1) Overgrazed uplands 2) Building on flood plain 3) Urban areas (concrete) 4) Roads and drains 5) Relief 6)
Mississippi Case Study The Mississippi Drainage basin is a huge river network running north to south in the USA. The natural flow of the river would see it meandering and flooding huge areas of land. To make the river more useful and a transport and trade link people have interfered with an managed the river course. The river has been straightened, shorted and walled in. However this has created other problems. Causes A period of prolonged heavy rainfall saturated the river basin, additional surface runoff to the channel meant that the river reached bank full and then levee full. The water level was the same height as the walls created by humans to hold the river in. Effects Primary -43 people were killed in the flood. -Fields flooded & crops lost. -Houses destroyed. -Forests and habitats destroyed Secondary -Stagnant water led to mosquito populations increasing. -Transport & Communication disrupted. -Economic damage totalling 12 billion, meant the economy and business could not operate as normal. -Certain crops being destroyed influence local and global prices in trade. Responses Short-term -50,000 were evacuated. -Sandbags distributed -Warning s issued via the media and the levee districts (people responsible for flood management). Medium-term -Clean-Up -Aid & Shelter Long-term -Re-building. -Afforestation. -Strengthen Levees. -Louisiana Spillway opened. 1. Using the figure above, give one physical cause and one human cause of flooding (2Mks) June 2011 (F) (Note this is a short question with NO command to explain) 2. Describe the effects of a flood you have studied. (6 marks) 3. Describe the responses to a flood you have studied (6 marks) 4. Explain how the effects of flooding differ between countries of differing levels of development. (8 marks)
CUE 11: You must be able to describe the location of flood events in the UK in the last 20 years and comment on the increased frequency of these events. MEDC case study: causes and effects of flooding in Boscastle, UK (2004) Causes Over 60 mm of rainfall (typically a month's rainfall) fell in two hours. The ground was already saturated due to the previous two weeks of above average rainfall. The drainage basin has many steep slopes, and has areas of impermeableslate causing rapid surface run-off. Boscastle is at the confluence (where tributaries meet) of three rivers - Valency, Jordan, and Paradise. A large quantity of water all arrived within a short space of time causing the rivers to overflow. The flooding coincided with a high tide, making the impact worse. Effects Homes, businesses and cars belonging to more than 1,000 people were swept away. Income from tourism was lost. This had an impact on livelihoods and the local economy. There were vast numbers of subsequent insurance claims. No lives were lost, partly due to the rapid response of the emergency services. CUE 13: You Describe need to the be effects able to of describe flooding flood in an management MDC you have strategies. studied (4Mks) June 2010
Hard engineering Dams, reservoirs and channel straightening. Soft engineering Flood warning, preparation, floodplain zoning, allowing flooding and the costs and benefits of these solutions. Soft Engineering does not involve construction and can be cheaper. This can make soft engineering economically achievable for LDCs and their impact on the environment is often reduced. Methods range from managed flooding, allowing rivers to flood certain areas, avoiding inappropriate development in flood risk areas or simply planning and predicting combined with a warning system. Soft engineering approaches make use of natural processes such as deforestation increases interception and water storage. 1. Hard and soft engineering strategies are used to manage flooding. Choose either hard engineering or soft engineering and explain why it is the better strategy (8Mks) June 2011 (Tip try SEE categories and refer to LDC/MDC) (This is tough but if you want to wait until Cue 15 you could use the information provided you will still need to show your understanding of soft engineering techniques) CUE 14: You need to be able explain the UKs increasing demand for water and the areas of the country with a deficit (lack of) and surplus. You should know about schemes and the need to transfer water to and from these regions.
The choropleth map on the left shows rain fall. The map on the right show the population. The main population centres are in southern England. The rainfall map shows there is clearly a surplus (Excess) of rainfall in western Scotland. This area however is sparsely populated and demand is low. Where demand is high there is a deficit as there a lack of rainfall. (You would quote figures, use compass direction, and regions). CUE 15: You need to be able to describe a case study of a dam or reservoir and successfully discuss the social, economic and environmental issues. These issues should be linked to future sustainability of our water supply. Kielder Water, Northumberland. North East England. A dam was constructed and the the Keilder valley was flooded. Water is a large artificial reservoir in Northumberland in North East England. It is the largest artificial lake in the United Kingdom by capacity and it is surrounded by Kielder Forest, the largest man-made woodland in Europe. Built 1975-1981 First flooded 1982 Social Improved water supply for the area for both domestic & industrial use. Environmental The old land was only poor quality farmland. Economic Jobs would be created as part of the building process; From tourism & recreation. Social Some people had to move, but only a few people had to be moved as the area had a low population. Environmental Some habitats and wildlife lost, though this was limited as land was mainly rough grazing. Economic Expensive, but a sustainable solution and is reliable. 1. Discuss the issues which result from building dams and reservoirs. (8 marks) 2. Explain how the UK manages to create a reliable water supply (6 marks) 3. Explain why the South of England have more hose pipe bans than the North. (6 marks)