rivers Flashcards
What are the stores in the hydrological cycle?
- ocean
- ice
- reservoir
- groundwater
What are the Flows in the hydrological cycle?
- run-off
- through flow
- ground water flow
- rivers
What are the Processes in the hydrological cycle?
- evapouration
- condensation
- interception
- transpiration
- precipitation
- percolation
What is the source?
Where the river begins
What is the watershed?
separates 2 drainage baisins
What is a confluence?
where 2 rivers meet
What is a tributary?
small rivers that join the main river
What is the mouth?
where the river flows into a sea or lake
What are the characteristics of the upper course?
- steep sided ‘v’ shaped valley
- hilly and barren
- not much human activity
- small channel
- small discharge
What are the characteristics of the middle course?
- meanders along a flat flood plain with lots of vegetation and fertile land
- wide deep channel
- larger discharge
What is are the characteristics of the lower course?
- very large channel
- fast flowing and high energy
- used for transport
- flat surrounding land
- large discharge
Why do rivers deposit their load?
because they lose energy
What is the discharge of a river?
volume of water flowing through through a river channel
How is river discharge effected?
- rock and soil type
- land use
- rainfall
- relief
How is river erosion effected?
- gradient
- rock resistance
- velocity
- discharge
On a storm hydrograph what shows the rainfall and what shows the discharge?
- rainfall bar chart
- discharge line graph
What is base flow?
starting and finishing flow of the river either side of the increased discharge
What is the erosional process of Hydraulic action?
the force of the river against the banks can cause air to be trapped in cracks and crevices. The pressure weakens the banks and gradually wears it away.
What is the erosional process of Abrasion?
rocks carried along by the river wear down the river bed and banks.
What is the erosional process of Attrition?
rocks being carried by the river smash together and break into smaller, smoother and rounder particles.
What is the erosional process of Solution?
soluble particles are dissolved into the river.
What is the Transportation process of Solution?
minerals are dissolved in the water and carried along in solution.
What is the Transportation process of saltation?
small pebbles and stones are bounced along the river bed.
What is the Transportation process of suspension?
fine light material is carried along in the water.
What is the Transportation process of Traction?
large boulders and rocks are rolled along the river bed.
What is deposition?
drop or deposit some of the material the river was carrying when it loses energy
What are the physical causes of floods?
- heavy/long periods of rain
- snowmelt
- steep slopes
- impermeable rock (doesn’t allow water through)
- very wet, saturated soils
- compacted or dry soil
What is peak discharge?
maximum discharge following rainfall event
What is peak rainfall?
maximum rainfall following rainfall event
What is the lag time?
the time between peak rainfall and peak discharge
What is the rising limb?
increasing discharge as storm water enters the river channel
What is the receding limb?
fall in discharge back to base level
What is channelisation (hard)?
reduces water friction with the bed and banks speeding up water flow and allowing the water to get away from an area quickly
What are retention ponds (soft/hard)?
Allows runoff to be temporarily stored and in turn lessens the risk of flooding
What is a flood warning system(soft)?
Allows evacuation of areas likely to flood and therefore reduction in damage by warning people in advance
What is a Dam (hard)?
Built to control discharge it hoilds back water allowing i to be released in a controlled way
What is a Afforestation (soft)?
Trees slow down the flow of water towards the river channel and also allow more interception
What are Levees (hard)?
Increases the potential maximum area of the river channel allowing it to hold more water before bursting its banks
What is flood plain zoning (soft)?
consider the floodplain and avoid building on the areas which are most regularly flooded.
What are the human causes of floods?
- urbanisation, because towns and cities have more impermeable surfaces
- deforestation, because removing trees reduces the amount of water intercepted and increases runoff
How is a waterfall formed?
When there are alternating layers of rock( Hard rock on top). The softer rock is eroded more quickly therefore undercutting occurs., eventually this leaves an overhang which collapses into the plunge pool.
How is a gorge formed?
The waterfall formation continues and it begins to retreat upstream leaving behind a steep sided gorge.
How is a meander formed?
Lateral erosion causes kinks in the river. The water on the outside bend moving more quickly meaning it has more energy to erode the river bank on the inside the water travels more slowly causes depostion. after time the bend get tighter and tighter.
How is an oxbow-lake formed?
When the water level is high (or during a flood) the meander is cut off and the river takes the easiest route. The ox-bow lake often drys up.
How are levees formed?
when a river flood it deposits the material its transporting, due it having less energy. The heaviest material is deposited closest to the river and over many flood this material builds up into levees.
How are deltas formed?
only under certain conditions at the mouth of a river. deltas are built up over time as sediment s are deposited at the mouth of the river causing the river to be split into 100’s of different channels.
How is a “v” shaped valley formed?
vertical erosion causes a narrow gorge the sides are weathered making it less steep and more of a “v” shape.
