Load: Material carried by a river.
Erosion: wearing away the landscape.
Solution: where dissolved chemicals are carried.
Suspension: Tiny particles of sediment carried in the river's current.
Saltation: Smaller stones or pebbles picked up & dropped again. 'skipping' motion.
Traction: large stones dragged along.
Abrasion: sand & pebbles are dragged along the river bed, or knock into by saltation, wearing away the bed.
Attrition: rocks & stones wear away each other as the knock.
Solution: where alkali rocks like Limestone are dissolved in acid rainwater.
Hydraulic action: fast-flowing water is forced into cracks, breaking up the bank overtime.
How Waterfalls are formed.
1. Occur when a river crosses a bed of more resistant rock.
2. Erosion of the less resistant rock underneath continues - undercutting the rock above it. River's energy creates a plunge pool.
3. Less resistant rock beneath is eroded more by abrasion and hydraulic action. Creates a Ledge, which overhangs and collapses.
4. Waterfall takes up a new position leaving behind a steep valley or gorge.
Weathering: breakdown of rocks in situ. This means it happens where the rock is. Rocks are broken by being chemically attacked & mechanically broken down.
- Biological: plant roots penetrate rocks in search of water.
- Physical: Physical forces break rock into pieces, freeze-thaw.
- Chemical: Chemical change or decay of solid rock.
Meanders: Middle course.
Meanders: have a Helical flow.
Sediment is deposited by slower currents.
Continued erosion of Meanders can lead to Ox Bow lakes.
Sheffield Floods, UK.
- Prolonged rain:
- Soil saturation:
- Confluence of several rivers:
- Physical landscape:
- The graph which shows how a river changes as a result of rainfall. It shows rainfall and discharge.
Time Lag: length of time between peak rainfall and peak discharge of the river.
Peak discharge: where river flows reaches a peak.
Falling Limb: where river discharge decreases.
Rising Limb: as water reaches the river, the discharge increases.
Hard engineering: structures built to defend from flood water.
- Build flood banks, Increase the size of the river channel, divert the river away from the city centre, increase the size of drains, increase maintenance budget.
Soft engineering: adapt to flood risks, and allow natural processes to deal with rainwater.
- Flood proofing, Flood plain zoning, Flood prediction & warning.