Rivers Flashcards
Abrasion (or corrasion)
The wearing away of the bed and bank by the load carried by the river.
Attrition
The wearing away of the load carried by a river, which creates smaller, rounder particles.
Hydraulic action
The force of air and water on the sides of rivers and in cracks.
Solution (or corrosion - not be confused with corrasion)
The removal of chemical ions, especially calcium, which causes rocks to dissolve.
Suspension
Small particles are held up by turbulent flow in the river.
Saltation
Heavier particles are bounced or bumped along the bed of the river.
Solution
The chemical load is dissolved in the water.
Traction
The heaviest material is dragged or rolled along the bed of the river.
Flotation
Leaves and twigs are carried on the surface of the water.
Deposition
The river deposits it’s load, heavier particles first, and then smaller, lighter ones later.
Features of deposition include: deltas, levees, slip-off slopes (point bars), oxbow lakes, braided channels and floodplains.
Oxbow lake
A meander that is closed off by deposition to form a oxbow lake.
Floodplain
An area covered by water when a river floods.
Levees
Raised river banks at the edge of a river.
Delta
A flat, low-lying deposit of sediment that is found at a river’s mouth.
Braided channels
Multi-channels
What are some physical causes of floods?
Climatological: - rain - ice melt - snow melt Part-climatological - coastal storm surges - estuarine interactions between stream flow and tidal conditions Other: - earthquake - landslide - dam failure
What are some human-related causes of flood/intensifying?
- more rapid discharge in urban area due to impermeable surface and increased number of drainage channels
- urbanisation and urban growth (increase in impermeable surfaces)
- floodplain developments (increasing risk of damage)
- bridges, dams, obstructions
- changes in vegetation cover, e.g. agriculture
- river engineering works, e.g. levees
- human-induced induced climate change
