Presentation on theme: "-We will revise the main topic areas of Water on the Land"— Presentation transcript:
1-We will revise the main topic areas of Water on the Land Rivers Revision-We will revise the main topic areas of Water on the Land
2Knowledge Checklist Know the processes of erosion Know the processes of transportationKnow how waterfalls and gorges are formedKnow how meanders and ox-bow lakes are formedKnow how flood plains and levees are formedKnow the factors that affect river dischargeKnow the physical and human causes of floodingKnow a case study of a rich and poor country floodKnow how hard and soft engineering can be used in flood managementKnow how water is used in the UK with areas of surplus and deficitKnow a case study of a reservoir in the UK
3The Profile of a RiverKey Idea: The shape of river valleys changes as rivers flow downstream due to the dominance of different processes.Processes of erosion – hydraulic action, abrasion, attrition, solution; vertical and lateral erosion.Processes of transportation – traction, saltation, suspension and solution.Deposition and reasons for it.Long profile and changing cross profile.
4The Water CycleIt is the main input to the drainage basin
5The long profile and the drainage basin The long profile of a river is a cross section from its source to its mouth. This whole area is known as the drainage basin.They are divided into three sections:Upper courseMiddle courseLower courseRiver gradient decreases gradually as the river flows downstream (ie. It becomes less steep)
6Drainage Basin Key words A river basin is the area of land drained by a river and its tributariesWatershed – an area of higher land separating two drainage basinsSource – the place where a river beginsTributary – a smaller river joining a larger oneConfluence – the place where two rivers joinMouth – the place where a river enters a lake or the sea
9Transportation Material is carried in the river in four ways: Traction: large stones are rolled along the river bedSaltation: smaller stones ‘bounce’ along the river bedSuspension: small particles of silt and clay float through the waterSolution: minerals are dissolved in the river
10DepositionDeposition is the dumping of material and happens when the river loses its energy. This may be during a dry spell, on the inside of a river bend, or when the river reaches the sea (readon for more on this).
11The Long Profile of a River L.Ob: to describe how a river changes from source to mouthThink aboutthe 2 pictures of rivers: why are they so different?
15Upper Course Vertical erosion is the main process. Valleys are v-shaped, interlocking spurs.Waterfalls are formed.Rapids are smaller scale feature formed where finer bands of varying resistance of rocks are found.
20WaterfallsA waterfall is a place on a river where the water flows verticallyThey tend to occur in the upper course of a riverSofter rock erodes quickly, undercutting harder rockHarder rock erodes more slowly, forming overhangOverhang eventually collapses – the waterfall moves upstreamSteep sided valley (gorge) is formedPlunge pool erodes under waterfall
21Landforms in Middle and Lower Sections: Meanders
44A DeltaSome rivers reach the sea in deltas, which form where river mouths become choked with sediment, causing the main river channel to split into hundreds of smaller channels or distributariesDeltas only form under certain conditionsThe river must be transporting a large amount of sedimentThe sea must have a small tidal range and weak currentsThe sea must be shallow at the river mouthFamous deltas consist of the Mississippi delta, The Ganges and Brahmaputra delta (Bangladesh) and of course the Nile delta.
45Flood Plains and Levees When a river continually floods, it spreads silt across the flood plain. Often this material piles up to form levees. Sometimes, humans make artificial levees to mimimise the impact of flooding.
46Flood Hydrograph Peak Rainfall Peak Discharge LAG TIME DISCHARGE (cumecs)RAINFALL mmtime
47River DISCHARGEDischarge is the volume rate of water flow, which is transported through the river channel.Measured in cumecs (cubic metres per second)
48The Flood Hydrograph – A = floods quickly (flash flood) B = slower rate of discharge, less likely to floodWHAT FACTORS AFFECT THE DISCHARGE LINE?
49Factors Affecting Water in a River Amount and type of rainfallPrevious weather conditionsLand useTemperatureRock typeRelief
50Describe 5 factors that might affect the lag time (time it takes river to flood)
51Describe 5 factors that might affect the lag time (time it takes river to flood) 1 = Deforestation2 = Urbanisation3 = Relief of land4 = Dam Building5 = Industry/Agriculture
52Contrast the hydrographs (3) Explain why the two hydrographs are different (4)
58Write a quick case study…. MEDC: UK Floods 2007Write a quick case study….What caused the floods? What were the main effects? What are the solutions?
59FLOODING IN AN LEDC – Bangladesh Case Study IMPORTANT DATES and DEVELOPMENT INDICATORS for BangladeshCAUSES of the flood:MANAGEMENT RESPONSES – can they reduce the impact?:EFFECTS of the flood on People and Environment:Remember SHORT and LONG TERM
60Hard Vs Soft Engineering Page 92 of bookRaise leveesDredge river bedsStraighten rivers
61Hard Vs Soft Engineering Zone off some areasBetter warning systems
67Reservoir Case StudyYou need to know one case study of a reservoir that provides water to people in the UKKielder Reservoir is in bookBiggests man-made reservoir in Europe.Was poor farmland, large valley with steep sides.Lots of rainfall and low population.Wild habitats were limited so little environmental damage.Supplies NE of England wit water.Lots of leisure industry there. Good for economy.