Presentation on theme: "Welcome to ‘Water on the Land’ Revision. The Syllabus Opposite is a copy of the syllabus for this unit of work. It should help you to highlight any gaps."— Presentation transcript:
The Syllabus Opposite is a copy of the syllabus for this unit of work. It should help you to highlight any gaps in your notes and learning
Main Case Studies Boscastle, Cornwall (2004) OR Summer Floods (2007) and Bangladesh (1998) Floods. The causes, effects and responses (flood management) to flooding. These are case studies of flooding in a rich part of the world and a poorer part – they show the different effects and responses to flooding. The River Tees. This is a case study of flood control (e.g. Yarm’s flood defence scheme). You need to know how threat of flooding is managed.. Kielder Water in Northumberland. A case study of a dam/reservoir where you need to consider the economic, social and environmental issues and the need for sustainable water supplies.
The main features of a drainage basin You need to know the key terms and their meanings. What is X? X = The Watershed
River discharge ‘What factors affect the discharge of a river?’ Discharge is the volume of water flowing in a river at any one time. This varies from day to day and season to season. What causes high river discharge? 1.High land (more rainfall, lower temperatures and less evaporation) 2.Steep slopes (fast runoff) 3.Granite rock (impermeable) 4.Bare rock (no trees to soak up water) 5.Built up areas with many hard surfaces
Changes in River profile You need to know how valley and channel cross section changes along a river: The channel becomes wider and deeper as the river flows down stream. The valley begins as a V shaped valley (vertical erosion) and ends as a wider U shaped valley (lateral erosion) Long profile valley cross section Channel cross section
The Upper course Four processes of erosion: 1.Hydraulic Power 2.Corrosion/solution 3.Corrasion/abrasion 4.Attrition Know what each one means…defining key terms are very common questions (use the revision glossary to help you learn them)
Landforms in the Upper course V shaped valleys Interlocking spurs Waterfalls and gorges Be prepared to identify these features on a photograph/sketch and able to draw label a sequence of diagrams to show the formation of a water fall
waterfall Interlocking spurs V Shaped valley Plunge pool Steep sides Gorge
Explain the formation of a waterfall (6 marks) Give reasons why something happens. Answers should set out the causes of a phenomenon and/or the factors which influence its form/nature. This usually requires an understanding of processes. Explanation is a higher-level skill than description and this is often reflected in its greater mark weighting. Set out purposes or reasons. So try and give 6 points if you can. At this level I would also expect linked statements in more complex sentences for example… ‘When water flows over horizontal bands of hard and soft rock, it is the soft rock that erodes more quickly making a ‘step’ in the river’s course…’
What to say You should begin by referring to horizontal bands of hard and soft rock; the hard rock forming the cap rock; differential erosion via abrasion, hydraulic action will cause soft rock to wear away faster than the hard rock; this will be undercut and an overhang will form and collapse - the water plunging over the steep drop forms plunge pool. Processes Key Terms
Level 1 (1-2 marks) Basic statements with limited sequence e.g. hard and soft rock appear next to each other, water flows steeply down hard rock. Level 2 (3-4 marks) Clear, more developed answer with more complete sequence and more appropriate terminology e.g. hard rock lies on top of soft rock and is eroded faster due to the power of the water. This undercuts the hard rock which collapses forming the waterfall. Level 3 (5-6 marks) Detailed, well developed answer with clear and complete sequence; appropriate terminology e.g. bands of hard and soft rock are horizontal; the overlying cap rock is eroded slower than the softer rock. Hydraulic action and abrasion are important processes of erosion. An overhang is formed (by undercutting) which eventually collapses as the weight of the overlying cap rock is too great, creating the steep drop of the waterfall (at the bottom of which is a plunge pool). May continue to retreat and formation of gorge.
The amount of load depends on 1.The volume of water – the greater the volume, the more load it can carry 2.The velocity – a fast flowing river has more energy to transport and can move larger particles 3.The local rock types – some rocks, e.g. shales, are more easily eroded than others, e.g. granite
Features of the middle course Meanders (know what meander migration is) and be prepared to label a cross section of a meander bend
The lower course This is where deposition takes place encouraged by: 1.A river carrying a large load (providing a great deal of material to be deposited) 2.A reduction in velocity 3.An obstruction (e.g. a river enters a lake and velocity falls) 4.A fall in the volume of river water (caused by a drought perhaps)
Main features Ox bow lakes Flood plains : be able to describe what one is and how it is formed. Below is a diagram showing the main features of a flood plain
What are levees and how are they formed? Levees are natural embankments of silt along the banks of a river, often several metres higher than the flood plain. They are formed by periodical flooding.
Explain, with the aid of a diagram(s), how levées are formed. (6 marks)
Level 1 (1-2 marks) Basic statements, limited sequence, e.g. the river floods and lays down silt that builds up into levées. May not be a diagram or if there is it is likely to be of limited use in the answer. Level 2 (3-4 marks) Clear statements and more idea of sequence and vocabulary, e.g. when the river floods onto its flood plain, the speed is reduced and silt is deposited. More is deposited on the river banks and after several floods it builds up into high banks called Levées. Diagrams likely to be clear but with perfunctory labels that do not add significantly to the account. (Max Level 2 if no diagram(s)).
Level 3 (5-6 marks) Answer may consist of heavily annotated Diagrams only or a combination. Account is detailed and in the correct sequence. Candidate recognises the finer details, e.g. the reasons for greater deposition on the river banks, rather than further away; the importance of coarse material being deposited first, the need for a river carrying a large load and for repeated flooding for their formation.
Revise land use in the R. Tees Human Activity in the Upper course Water supply (reservoir) Sheep farming Tourism Industry Human Activity in the lower course Urbanized Industries such as steel making, ship building… Flat and cheap land Transport (to receive oil and gas supplies from the N.sea)
Management in the lower Tees valley 1.The Tees Barrage 2.Dredging 3.Cutting meanders 4.Yarm’s flood defence scheme 5.Improved flood warning systems 6.New development discouraged
River regimes – flood hydrographs Be able to read one and label its main features
Water supply and demand in the UK ¾ of the UK supply comes from mountain lakes, upland reservoirs and rivers The rest comes from underground stores in porous rocks Demand for water is rising as the UK’s population is increasing About half of all our water is used to generate electricity! Both thermal and nuclear power stations need water for cooling. Demand for water is highest in the most densely populated places in the UK such as London and the South East. However these are just the places where water is in short supply
Why build Kielder Reservoir? Physical reasons 1.River North Tyne has large valley with flat floor and steep sides 2.High annual precipitation (1370mm) 3.Limited variety of wildlife habitats to lose Human reasons 1.Not many people had to be re housed as this was a sparsely populated area 2.Land lost was only poor quality farmland Of course there was a lot to gain by building this reservoir………
Meeting the demand We can all save water (fit water meters and dual flush toilets in new homes, get water companies to reduce leaks, buy water efficient appliances) BUT in the end, water has to be transferred from the West of the UK (where it’s wettest!) to the east (where most people live. This done by building pipelines (expensive), aqueducts (now old and in need of costly repairs) or by river (the cheapest way). This can have environmental impacts too as transferring water with different PH etc. can harm fish.
Case study Kielder Water Largest reservoir in the UK 10 km long In Northumberland on Scottish border Opened in 1982 Was originally built to supply water to the steel industry on Teeside Now supplies water for Tyne and Wear area via rivers and tunnels Has it been a success? Was it worth the money? The reservoir is successful because it has helped to re-vitalise industry in the area, it has attracted many visitors to the area for water based leisure, there are more jobs available in tourism, forestry and the water industry and homes in the region do not suffer hose pipe bans when there is a drought
Flood defence methods Build dams and reservoirs Warn people Plant trees Dredging Raising levees Straightening rivers Land use zonation preparation OR…do nothing! You need to know which are hard engineering solutions and which are soft engineering?
Describe one way in which the risk of flooding might be reduced 2 marks Any valid scheme. 1+1, e.g. build a dam (1), this would store excess water (1) which would reduce peak discharge (1). Build embankments (1) this would increase amount of water the river could hold.
Know the causes, effects and responses of two floods UK Floods, Summer 2007 /Boscastle (MEDC) (LEDC) Bangladesh, 1998/2004
UK Floods, Summer 2007 Key facts Summer 2007 was the wettest since 1766 400mm rain fell in May, June and July The saturated ground could not take any more water so by the end of June places like Hull, Doncaster, Sheffield and Tewkesbury (opposite) were severely affected. 13 people died (swept by fast running water) RAF rescued many people 1000s stuck in cars on the M5 motorway 56,000 homes and 7000 businesses flooded 350,000 in Gloucestershire had no fresh water because the water treatment plant was flooded Many were left without power due to the electricity sub station being flooded One year later there were still 5,500 families living in caravans unable to return to their homes
Boscastle 2004 Key facts 16 th august 2004 200mm rain fell in 4 hours In one hour 90mm fell Water poured down steep hillsides of Rivers Valency and Jordan Flash flood event 3m wall of water swept through Boscastle, Cornwall Cars washed into the sea, riverside shops and houses destroyed Helicopters lifted 80 people to safety £800,000 flood defence scheme completed in 2005 including channel and drain improvements, widening bridges, clearing wooded areas
Effects of Flooding in Bangladesh : The 1998 Floods Flood waters swept away and caused severe damage to railways, roads and bridges. This cut communications and made rescue operations difficult. Water supplies were contaminated by dirty water and sewage and fresh water became scare. Farmland was flooded and over 50% of crops in flooded areas were lost. Many people lost their homes and belongings Many were killed (over 2000). Deaths were not only due to being swept away by the flood waters but also secondary effects of flooding, such as disease spread in contaminated waters and the lack of food resulting in starvation in some cases. There were great financial loses, such loss of income by shops and businesses which were unable to sell good or services and the costs incurred due to damaged infrastructure (roads, buildings etc.) As an LEDC the results of flooding in Bangladesh were particular devastating not only due to its dense population but the lack of resources available to cope with such a disaster. Flood defence is a problem and the government cannot afford costly schemes. Responses to the flooding Short Term Relief Farmers provided with free seed from the government Foreign aid was given (including £21 million from the UK government) Water Purification tablets were brought by money raised by the WHO (World Health Organisation) Food aid was given (including foreign and national aid) Long Term Flood Protection Measures Flood protection shelters built (able to provide shelter in times of flood but have on other occasions been swept away by floods) Flood embankments built along the river. (7 500km built since 1947) Not always successful. Upstream dams proposed. These would hold back peak flow, but the costs of construction are very high. Reduce deforestation in headwater areas. Making provision for emergency flood warning systems to give warnings and organise sufficient rescue and relief services (provision of emergency medical and food supplies).
Possible longer answer questions… 1.Describe and explain the causes and effects for a flood that you have studied. 2.Describe how the responses to a flood in an LEDC may be different to an MEDC.
Tips! Learn all key terms (e.g. alluvium, saltation etc.) Be familiar with diagrams and be prepared to draw and annotate them Give evidence to support your case studies Visit the GCSE Bite Size website and revise the rivers section See me/ log on to http://www.aqa.org.uk/qual/gcse/geo_a_assess. php for past papers. Also available on shared area with this Powerpoint!! http://www.aqa.org.uk/qual/gcse/geo_a_assess. php