Floods

Front 1

What do streams do?

Back 1

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

Front 2

How do streams balance the variables it deals with?

Back 2

Equilibrium, change causes compensating actions, variables include discharge, gradient, channel pattern and avaliable sediment

Front 3

What does cross sectional shape have to do with stream discharge?

Back 3

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.

Front 4

What happens if there is too much discharge of water?

Back 4

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.

Front 5

What is meandering? How does it form?

Back 5

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

Front 6

What does too much load do to a stream?

Back 6

Insufficent water carries the extra sediment away, the gradient increases and the stream flows faster and forms a braided stream

Front 7

What is the flood plain?

Back 7

The floor of streams during floods wich are built by erosion and deposition.

Front 8

What are natural levees?

Back 8

The build up of coarser grained sediment that is deposited when the stream overtops its banks during a flood.

Front 9

What role does velocity play in the formation of natural levees?

Back 9

The velocity is high as coarser sediment is deposited. The velocity of the water decreases graduall on the flood plain.

Front 10

What are terraces caused from?

Back 10

The regional uplift of lowering the regional base level or a drop in sea level.

Front 11

What is lag time?

Back 11

The time difference between when heavy precipitation occurs and when peak discharge occurs in the streams draining an area

Front 12

What are factors that influence lag time?

Back 12

-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

Front 13

What are the different flood styles?

Back 13

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

Front 14

What is a flash flood?

Back 14

A flood that can wash out the road and happens quickly from steady rainfall

Front 15

Why are flash floods dangerous?

Back 15

They occur quickly and can lift a car

Front 16

Where do floods occur?

Back 16

Mainly near the Mississippi River as well as other large rivers

Front 17

What are two primary hazards of flooding?

Back 17

Massive amounts of erosion can cause buildings to collapse and crops, livestock and humans drown

Front 18

What is a secondary hazard of flooding?

Back 18

Disruption of services, polluted drinking water and food shortages

Front 19

What are two tertiary hazards associated with flooding?

Back 19

Lost jobs, increase of insurance rates

Front 20

What are societal responses to flooding?

Back 20

Structural responses, dams to trap flood water, levees, channelization, sand bagging and nonstructural responses such as insurance programs, evacuation planning and education

Front 21

What is channelization?

Back 21

Decreasing the cross-sectional area of the stream, causing flooding

Front 22

What are the effects of development?

Back 22

Channelization, subsidence, storm sewers and reduction of infiltration