River processes & landforms

IGCSE River Processes

1. River Processes & Landforms Chapter 5

2. River Processes Erosion removes material from a river bed making it deeper/wider These pebbles, sand, silt, etc. get transported downstream (river’s load) Deposition occurs after a river no longer has enough energy to carry the load and drops it on the river bed-boulders first, silt & mud last

3. How a River Transports

4. Worksheet

5. Factors Affecting River Work Velocity/energy-the faster the river the larger the material able to be transported After rain rivers may look brown due to suspension

6. Factors Affecting River Work Volume-the more water the greater the volume of the load Bedrock-harder rocks-i.e. granite- erode slowly, soft rocks-shale-erode easily & some rocks- i.e. limestone- can be dissolved completely

7. Deposition Occurs when rivers lose velocity Decrease in the gradient Decrease in river flow as water drains after a heavy rain River meets the sea/lake River flows slower on the inside of bends

8. The River Channel

9. Upper Course of a River Source Where the river starts in a highland or mountainous area Vertical erosion can be great in some areas and create gorges, canyons, potholes Potholes-smooth rounded hollows formed by stones trapped in the hollows of a river bed

10. Upper Course of a River Rapids Form where the water is shallow and the river bed is rocky & irregular making the water rough Usually in steeper areas Can make river travel difficult unless white water rafting/kayaking

11. Upper Course of a River Waterfalls & Gorges

12. Victoria Falls Zambia & Zimbabwe

13. https://www.youtube.com/watch?v=YP1J1csZaCM

14. Waterfalls & Gorges Positives Brings in tourists Hydroelectricity Negatives Can cause navigation problems, makes the river difficult to cross

15. Upper Course Interlocking Spurs Narrow valleys force the river to create a winding path

16. Middle and Lower Courses As the river valley begins to widen and become less steep Begin to see more lateral (sideways) erosion Vertical erosion may stop completely by the time we reach the lower course

17. Meanders & Oxbows

18. Meanders & Oxbow Lakes

19. Floodplains & Levèes Flat land next to a river liable to flood Occasionally the river flows above the level of the surrounding plain but is enclosed by raised embankments called levèes

20. Floodplains & Levèes

21. Deltas Low-lying flat marshy land where a river meets a sea/lake Formed from a river with carrying a lot of sediments that meets a still sea/lake and the sediments build up May cause distributaries

22. Mississippi Delta, USA

23. Mahakam River, Borneo

24. The Long Profile of a River A line drawn from the source of the river to the mouth showing how the gradient changes Typically steep in the upper course and more gentle and smooth in the lower course Erosion & deposition remove irregularities in the profile making it smooth and concave

25. Long Profile

26. Activity

27. Living in River Flood Plains & Deltas Often densely populated Offer flat land (easy to build) Fertile soils River valleys are natural route ways Navigable rivers allow transport & trade Provide drinking water and food source

28. Living in River Flood Plains & Deltas Tropics can suffer from diseases carried by insects i.e. malaria (mosquitoes) & sleeping sickness (tsetse flies)

29. https:// www.youtube.com/watch?v=4aVUrGO97Zg

30. Flooding Discharge-the volume of water flowing down the river at any one time W hen the discharge can no longer be contained within the channel & overflows to the surrounding area it floods Dense population can make flooding severe When it rains, very little of it actually falls into the river, so where does the water come from?

31. Flooding

32. Activity

33. Factors Affecting Discharge Rainfall Relief Rainwater runs over steep slopes vs. infiltration on gentle Land Use Weather Conditions Hi-temps reduce discharge Rock & Soil Type Permeable vs. impermeable

34. Hydrographs Graph showing how a river responds to a storm Shows rainfall and discharge

35. Flood Prevention Planting Vegetation Planting vegetation (trees) allows rainwater to be taken in by roots & go out through transpiration Acts like a sponge that releases water slowly so flood peaks are reduced

36. Flood Prevention Reservoirs can trap water and release it slowly

37. Flood Prevention Straightening the Channel Shortens the river and gets the water away faster.

38. Kissimmee River, Florida USA

39. Flood Prevention Artificial Levèes Increase the capacity of the channel Usually banks are strengthened with concrete or stone so less likely to break

40. Flood Prevention Dredging the Channel By making it deeper this increases the capacity and makes it less likely to overflow

41. Flood Prevention Bridge Design Bridges with wide pillars and walls on top act like dams which hold back water; modern bridges are slim and prevent this from happening

42. Flood Prevention Wash Lands Control land on flood plains areas for recreation instead of residential to minimize damage

43. Cause & Effects

44. Textbook Pg. 132-137 #7