4 WHAT ARE WE GOING TO LEARN? What is a drainage basin?Why is a drainage basin like a kitchen sink?What are the four processes of erosion in rivers?What are the four processes of transportation in rivers?
5 THE DRAINAGE BASIN Dyfi A drainage basin is an area of land that is drained by a river and its tributaries.DRAINAGE BASIN
6 THE DRAINAGE BASIN WATERSHED Nature’s ‘kitchen sink’ The higher land that forms the edge, or boundary, of a drainage basin is called the watershed.Nature’s ‘kitchen sink’WATERSHED
7 Drainage basins act like nature’s kitchen sinks. THE DRAINAGE BASINAll the rain that falls within a drainage basin flows into a single river channel that flows to the sea (or lake).Drainage basins act like nature’s kitchen sinks.
9 River Basin FeaturesWatershed the area of high land forming the edge of a river basin.Source where a river begins.Mouth where a river meets the sea.Confluence the point at which two rivers meet.Tributary a small river or stream that joins a larger river.Channel this is where the river flows.Drainage Basin this is the area of land drained by a river and its tributaries.
12 THE RIVER COURSEUPPER COURSEMIDDLE COURSELOWER COURSE
13 RIVER PROCESSES Rivers play a big role in shaping our landscape. They are able to do this because they have energy.This means that they can do work.The work they do is erosion and transportation.When they run out of energy they have to stop doing work, so they drop what they are carrying. This is called deposition.
14 EROSION PROCESSES Erosion is the wearing away of the river bed, river There are four processes of river erosion:attritioncorrasioncorrosionhydraulic action
15 TRANSPORTATION PROCESSES There are four processes of transportation:tractionsaltationsuspensionsolution
18 THE SOURCE The source is the start or beginning of a river. The source of a river is usually found in the hills or mountains.
19 Water can sink through gaps in the rocks SPRINGSrainWater can sink through gaps in the rocksUnderground water emerges where the rock type changesPermeable rock ie LimestoneRocks are saturatedImpermeable rock ie ClaySpring
20 THE RIVER COURSEUPPER COURSEMIDDLE COURSELOWER COURSE
21 UPPER COURSE CHARACTERISTICS steep valley sidessteep channel gradientnarrow valley floornarrow, shallow channel
22 Upper Course Characteristics large, angular stones and boulders
23 UPPER COURSE CHARACTERISTICS turbulent river flow at a section of rapids
24 Upper Course Landforms a typical V-shaped valley
25 Key Features:V-shaped valleyA steep sided and narrow valley that is formed due to vertical erosion. The load of the river cuts downwards and deepens the bed of the river.
26 Upper Course Landforms a typical V-shaped valley
44 At the middle stage of the river the valley sides become less steep The river is now wider and deeperIt does not flow at the same speed throughout its middle course, some parts are slower, some are faster
49 Why do rivers meander (bend)? Copy the diagram above and put the following labels in the correct place:Deposition Fast flow of river Shallow waterRiver Cliff Lateral Erosion Slow flow of river Deeper water River beach (Slip-off slope)2. Describe why one side of the river bend is different from the other.
55 The river erodes the outside of the bend and deposits on the inside so its course is changing. This erosion narrows the neck of the meander.Often during a flood the river will cut through the neck.The river continues in the new bed and the meander is abandoned. New deposition seals off the ends and the cut-off becomes an ox-bow lake.
59 1. When a river with a very low gradient floods a lot of silt is deposited on the river banks and much less on the flood plain.2. Frequent flooding continues this build up of silt. When the river is flowing normally it deposits in the river bed.3. This raises the river above the flood plain but, usually the built up levées protect the plain from flooding.