RIVERS AS AGENTS OF EROSION, TRANSPORTATION AND DEPOSITION You should be able to:

1. 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.

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

3. TASK: Complete your copy of the table Use the information on pages 56  65 to help you.

5. 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.

6. NOTE: The BOLD and underlined features are most likely to be asked. You are often given a choice.

7. FEATURES OF THE UPPER COURSE:

8. TASK: Make a neat copy of figure C (page 10 Connections) Use the key to annotate your diagram 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

9. The Upper Course Tees Etive Tees Etive North Esk

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

11. 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

12. Middle Course - Meanders

13. Large Meanders

14. Formation of an oxbow lake

15. NARROW MEANDER NECK FUTURE OX-BOW LAKE

16. 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