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River processes
1) Rivers display different characteristics in their upper, middle, and lower courses. The upper course has a V-shaped valley and vertical erosion, forming waterfalls and gorges. The middle course has a wider valley and more lateral erosion forming meanders. The lower course has an even wider floodplain and well-developed meanders forming ox-bow lakes. 2) Meanders form through lateral erosion on the outside bend of rivers where current is fastest, undercutting the bank to form cliffs. Deposition occurs inside bends where current is slower, creating slip-off slopes. Over time, meander loops migrate laterally across the floodplain. 3) In estuaries near
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River processes
- 1. River features? Are facial featuresthe same thing for rivers? 1
- 2. River Features Rivers areeroding, transporting and depositing constantly. The river can be divided into 3 sections – Upper Course at the Source, Middle Course and Lower Course at the Mouth of the river. The river displays different characteristics at each section. 2
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- 4. Upper valley characteristics “V”shapevalley, mostly vertical erosion Interlocking spurs Narrow, shallow channel, low velocity and discharge Large rocks that come from upstream and from valley sides 4
- 5. Interlocking spurs, Robinson, LakeDistrict An upper course valley often has interlocking spurs, and steep valley sides 5
- 6. River load inupper course Why are they rounded? 6
- 7. River load inupper course Why are they rounded? Boulders are large and semi-rounded, due to attrition within the load and abrasion with the stream bed and banks 7
- 8. Waterfall formation Look atthe diagram, How is a waterfall formed? 8
- 9. Upper Course: Waterfalls& Gorges Waterfall and Gorge 1 (OBLIQUE AERIAL VIEW) EROSION TYPE: Vertical and Headward 9
- 10. High Force waterfall,R. Tees Waterfall creates gorge as it recedes upstream by eroding the base and neck Plunge pool 10
- 11. Upper Course: Potholes Pothole s EROSION TYPE: Vertical (byEDDY CURRENTS) Boulders broken off by erosion that sit on the river bed create swirling eddy currents as the water flows past as the river is not strong enough yet to move the boulders by TRACTION. These eddies swirl the boulder round and erode a pothole in the river bed by ABRASION. 11
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- 14. Middle course, R.Tees HOW DOES THIS DIFFER FROM THE UPPER SECTION? 14
- 15. Middle course, R.Tees Valley opens out, more gentle slopes, wider valley bottom First signs of meanders River channel wider, deeper, greater velocity and discharge 15
- 16. Meandering Rivers WHAT ISA MEANDER? 16
- 17. Middle Course: Meanders Meanders 1 (AerialView) Meanders are formed because the current swings to the outside of a bend and concentrates the erosion there. Deposition occurs on the inside of the bed where there is not enough energy to carry load. EROSION TYPE: Lateral
- 18. Middle Course: Meanders2 Meanders 2 (Profile View / Cross Section X - Y) EROSION TYPE: Lateral This cross section clearly shows the eddy current (near ’X’) formed by the velocity of the river being concentrated on the outside of the bend. These UNDERCUT the bank causing the formation of a RIVER CLIFF. On the inside (NEAR ‘Y’), a SLIP-OFF-SLOPE is formed where current is too slow to carry any load.
- 19. Meander, R. Lavant, Chichester WHICHWAY IS THIS MEANDER MOVING? Slip-Off Slope Pebble deposits on the inner meander bend where there is low energy Floodplain River Cliff 19
- 20. WHERE IS EROSION TAKINGPLACE? River Cliff F A E B Slip-off slope C } Meander loop D WHERE IS DEPOSTION TAKING PLACE? 20
- 21. What happens tothe river when it moves to the middle course Gradient becomes less steep River continues to erode vertically a bit but more LATERAL erosion now occurs in MEANDERS The meanders MIGRATE. What do you think that means? Name three effects it have on the valley. 21
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- 23. Lower Course: SevernValley HOW DOES IT DIFFER FROM THE MIDDLE COURSE? 23
- 24. Lower Severn Valley Verywide floodplain Very gentle valley side gradients Well developed meanders with bars in the channel indicating high sediment load 24
- 25. Lower Course: Ox-bowlake Ox-Bow Lake 1 (Aerial View) EROSION TYPE: Lateral Ox-bow lakes are formed when two meander RIVER CLIFFS are being eroded towards each other. These will eventually meet, causing the river to then flow across the bottom of the diagram.
- 26. Lower Course: Ox-bowlake 2 Ox-Bow Lake 2 (Aerial View)
- 27. Ox Bow lakeon Mississippi 27
- 28. The Nile Deltafrom space River Nile 28
- 29. Estuary Formation HOW DOESTHIS DIFFER FROM A DELTA? RAISED VALLEY SIDES 29
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