RIVERS AS AGENTS OF EROSION, TRANSPORTATION AND DEPOSITION You should be able to: Describe the changes in river characteristics as it flows downstream along its valley. Describe the fluvial processes of erosion, transportation and deposition.

Add a line to show the profile of the typical river profile.

Complete your copy of the table Use the information on pages 56  GRADIENT Decreases downstream as vertical erosion decreases downstream Progressively gentler gradients DISCHARGE Increases downstream as: more tributaries join, more water enters through baseflow and throughflow VELOCITY Depends on channel slope – steeper the slope the faster the river, rougher the sides the greater the friction and slower the river VALLEY SHAPE V-shape to more gentle gradient as vertical erosion decrease – steep sides. Interlocking spurs EROSION (VERTICAL / LATERAL) Vertical in the upper course as river cuts into the bedrock – moving towards base level LOAD Increases in quantity as river moves downstream due to erosion Decreases in size and angularity downstream (attrition) TRANSPORT More energy is given to transportation in the middle course as the load of the river increases TEXTBOOK PROFILE AFFECTED BY: Waterfalls, local base levels TASK: Complete your copy of the table Use the information on pages 56  65 to help you.

EROSION TRANSPORTATION DEPOSITION Corrasion / abrasion Traction Entering the sea Hydraulic action Saltation Overflow the banks Corrosion Suspension Inside bend of meander Attrition Solution Reduction in discharge (drought) Sudden decrease in gradient (base of waterfall)

RIVERS – PHYSICAL FEATURES As in the lithosphere unit you are often asked to explain how physical features are formed. Important tips: Always use annotated diagrams in your answer, even when not specifically asked for them. Practice drawing diagrams when you are revising. Use simple line drawings – they are much quicker and easier to draw than artistic line diagrams. Give plenty of detail on the processes – do not be fooled into thinking ‘this is easy – I have done this in Standard Grade’. There may be twice as many marks for a similar question at Higher (c.12 marks for one feature). When given a choice of features, choose the one you can write most about.

RIVERS – PHYSICAL FEATURES UPPER COURSE MIDDLE COURSE LOWER COURSE Waterfalls Meanders Pot Holes Ox-Bow Lakes Interlocking Spurs Levee Braiding River Terrace Flood Plain NOTE: The BOLD and underlined features are most likely to be asked. You are often given a choice.

FEATURES OF THE UPPER COURSE:

Hard rock overlying soft rock Soft rock erodes more easily WATERFALL Hard rock overlying soft rock Soft rock erodes more easily (DIFFERENTIAL EROSION) Eventually soft rock is worn away This causes undercutting of hard rock Nothing to support the harder rock which collapses The process is repeated and the waterfall moves upstream. Headward erosion Hydraulic action and abrasion lead to a deep plunge pool (fully explain these processes) Erosion processes should be mentioned throughout answer Differential erosion is important Answers could be in the form of a series of annotated diagrams Diagrams should show process: Before During After TASK: Make a neat copy of figure C (page 10 Connections) Use the key to annotate your diagram

The Upper Course Tees Etive Tees Etive North Esk

WATERFALL RETREATS . . UPSTREAM . . OVERHANG PLUNGE POOL UNDERCUTTING OF SOFT ROCK

Sinuosity – tendency for river to follow a winding path MEANDERS Development of pools (deeper flows / slower) and riffles (shallower flows / faster) lead to initial deviance from straight river course Sinuosity – tendency for river to follow a winding path Coriolis effect Erosion on the outside of the bend due to faster and more powerful flow by hydraulic action Deposition on the inside of bends due to slower, less powerful flow Helicoidal (corkscrew) flow removes material Migration of meanders downstream Undercut banks / river cliffs and slip-off slopes / river beaches formed in this process Cross section diagram and process diagrams COPY FIGURE 3.35 ON PAGE 64 Coloured Pencils – The key is important! SQA

Middle Course - Meanders

Large Meanders

Formation of an oxbow lake

NARROW MEANDER NECK FUTURE OX-BOW LAKE

River wears away outside bend of meander (lateral erosion) OX-BOW LAKE Small crescent shaped lake is formed from the over-development of meanders River wears away outside bend of meander (lateral erosion) Neck of meander narrows River breaks through – usually during flood conditions Meander is breached as river takes shorter/direct route Deposition of sediment on river banks results in ox-bow lake being cut-off LEVEE Raised beaches Formed by materials deposited during flooding Level rises over time Heaviest material deposited first resulting in a sloping affect as levee moves away from river TASK: Make a neat copy of figure 3.36 Including key