Rivers Flashcards
Define transportation.
the load (mud, rocks, etc) that have been eroded by a river and are carried downstream.
Define deposition.
River dopping eroded material on the river bed when it can’t carry it anymore.
Define corrasion (abrasion).
sand and pebbles are dragged along the riverbed, wearing it away.
Define hydraulic action.
fast-flowing water is forced in cracks, breaking up the bank over time.
Define attrition.
rocks and stones wear each other away as they knock together, becoming smaller and rounder.
Define solution.
rocks such as limestone are dissolved in acid rainwater.
Define saltation.
smaller stones/pebbles are picked up and then dropped again.
Define traction.
large stones are dragged along.
Define bedload.
heavier material is carried along the bottom.
Define suspension.
tiny particles of sediment are carried in the river’s current.
What are the three factors affecting the work carried out by a river?
- Velocity of the running water
- Volume of running water
- Bedrock along the course of a river
Define discharge.
volume of water flowing down the river at any one time. measured in cubic meters per second.
What are the three river channel types?
1) meandering
2) straight
3) braided
What is the source?
the place where the river starts.
What are potholes?
smooth, rounded hollows in the bedrock of the river bed caused by vertical erosion. formed by stones trapped in hollows.
Where do rapids form?
where water is shallow and riverbed is rocky and irregular.
Where do waterfalls and gorges form?
Where hard rock is on top of soft rock in a river. Soft rock erodes quickly and develops into a plunge pool. Splashing water and eddy currents in pluge pool undercut hard rock later until it creates an unsupported overhang and collapes. This process repeates for centuries as the waterfall retreats upstream and a gorge is created.
Define levee.
natural embankment on sides of rivers created by deposition.
Define flood plain.
flat area next to river liable to flooding.
Define delta.
flat area where river meets sea/lake.
Define distributary.
smaller channels of the river that form a braided pattern.
What is an oxbow lake?
a meander that has been cut off from the river.
Where are deposition and erosion on a meandering river?
deposition on inside of river and erosion on outside.
Define drainage basin.
an area of land that catches rain and snow, and drains into a common body of water.
Define watershed.
an imaginary line between two drainage basins that separates basins from each other. they are usually along the ridges of mountains.
What are four benefits of rivers and river flood plains?
- flat land for roads, buildings, and agriculture
- mineral-rich and fertile soils
- river valleys are natural route-ways
- rivers provide transportation routes, water, and fish
What are two problems caused by rivers and flood plains?
- Disease carried by insect pests
- Liable to flooding
What are the five factors affecting discharge?
- rainfall
- relief
- land use
- weather conditions
- rock and soil type
What is antecedent rainfall?
rain that’s already happened so the ground is saturated and more rain will flow as surface run-off towards river.
What are five methods of flood prevention and defences?
1) planting vegetation
2) reservoirs
3) straightening the channel
4) dredging the channel
5) artificial levees
