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22 Cards in this Set

  • Front
  • Back
What do streams do?
1) Carry most of the water that goes from land to the sea
2) Carry billions of tons of sediment to lower elevation
3) Streams dissolve material into ions
4) Part of the erosional process
5) Major source of water
How do streams balance the variables it deals with?
Equilibrium, change causes compensating actions, variables include discharge, gradient, channel pattern and avaliable sediment
What does cross sectional shape have to do with stream discharge?
The shape varies with the position in the stream and the amount of discharge the deepest part of the stream is where the velocity is the highest.
What happens if there is too much discharge of water?
Stream bottom erosion, if there is too much water the flow is faster, in order to correct this the stream will use excess energy to erode the bottom.
What is meandering? How does it form?
When there is too much discharge the streams responds by increasing the sinuosity by meandering and cutting the banks, using the excess energy to leghten the path
What does too much load do to a stream?
Insufficent water carries the extra sediment away, the gradient increases and the stream flows faster and forms a braided stream
What is the flood plain?
The floor of streams during floods wich are built by erosion and deposition.
What are natural levees?
The build up of coarser grained sediment that is deposited when the stream overtops its banks during a flood.
What role does velocity play in the formation of natural levees?
The velocity is high as coarser sediment is deposited. The velocity of the water decreases graduall on the flood plain.
What are terraces caused from?
The regional uplift of lowering the regional base level or a drop in sea level.
What is lag time?
The time difference between when heavy precipitation occurs and when peak discharge occurs in the streams draining an area
What are factors that influence lag time?
-If the amount of rain is high over a short time then the lag time is short
-If the amount of rain is high over a long time then the lag time is longer
-The lack of infiltration and interception reduces lag time
What are the different flood styles?
1) A local thunderstorm can form and unleash a flash flood
2) Abundant rainfall can cause regional flooding
3) Storm surges of tropical cyclones at the coasts
4) The break up of winter ice on rivers
5) Short lived natural dams made by landslides fail
6) Human built dams and levees fail
What is a flash flood?
A flood that can wash out the road and happens quickly from steady rainfall
Why are flash floods dangerous?
They occur quickly and can lift a car
Where do floods occur?
Mainly near the Mississippi River as well as other large rivers
What are two primary hazards of flooding?
Massive amounts of erosion can cause buildings to collapse and crops, livestock and humans drown
What is a secondary hazard of flooding?
Disruption of services, polluted drinking water and food shortages
What are two tertiary hazards associated with flooding?
Lost jobs, increase of insurance rates
What are societal responses to flooding?
Structural responses, dams to trap flood water, levees, channelization, sand bagging and nonstructural responses such as insurance programs, evacuation planning and education
What is channelization?
Decreasing the cross-sectional area of the stream, causing flooding
What are the effects of development?
Channelization, subsidence, storm sewers and reduction of infiltration