VOCAB GHC Ch 13: Floods

Question 0

Regional floods

Answer 0

Huge, long-lasting floods in large river valleys with low topography resulting from prolonged heavy rains over an extensive region. They cause heavy economic losses.

Question 1

Flash Flood

Answer 1

A local and sudden flood of relatively great volume and high velocity that lasts for a short time following a few hours of intense rainfall. Flash floods cause many deaths.

Question 2

Gradient

Answer 2

The slope of a stream channel bottom; change in elevation divided by distance. Gradient increases with steeper slope.

Question 3

Base level

Answer 3

The lowest point to which a stream or river can flow, often referred to as the ‘mouth’ of the river; usually sea level.

Question 4

Equilibrium

Answer 4

A state of balance in a system; a condition in which opposing processes are so balanced that changes cause compensating actions.

Question 5

Discharge

Answer 5

The volume of water flowing in a stream per-unit of time.

Question 6

Sinuosity

Answer 6

The length of a stream channel divided by the straight-line distance between its ends.

Question 7

Load

Answer 7

The amount of material moved and carried by a stream.

Question 8

Meander

Answer 8

The curves, bends, loops, and turns in the course of an underloaded stream that shifts its bank erosion from side to side of its channel.

Question 9

Braided stream

Answer 9

And overloaded stream so full of sediment that water flow is forced to divide and recombine in a braided pattern.

Question 10

Graded stream

Answer 10

An equilibrium stream with an evenly sloping bottom adjusted to efficiently handle water flow (discharge) and sediment (load) transport.

Question 11

Floodplains

Answer 11

The nearly flat lowlands that border a stream and act as the stream bed (the physical confine of the normal water flow) during floods.

Question 12

Feedback

Answer 12

A change in the system that provokes further changes.

Question 13

Positive feedback

Answer 13

Occurs in nonequilibrium systems where one changed triggers more changes in the same direction. The vicious cycle.

Question 14

Negative feedback

Answer 14

Occurs in equilibrium systems where one change triggers another change that tends to negate the initial change and restores equilibrium. Example: when too much water pours into a channel, increased erosion lowers the gradient to slow the water flow and maintain equilibrium.

Question 15

Recurrence intervals

Answer 15

The average time interval between floods or earthquakes of a given size.

Question 16

Avulsion

Answer 16

The abrupt change in the course of the stream and the adoption of a new channel.

Question 17

Levees

Answer 17

A natural or human built embankment along the side of the stream channel.

Question 18

Floodway

Answer 18

River channels and adjacent lowlands reserved to handle floodwater diverted from a large river.

Question 19

Flood stage

Answer 19

Water level at which a river overflows it’s banks and levees.

Question 20

Hydrograph

Answer 20

A plot of water volume, height, flow rate, etc., with respect to time.

Question 21

Riprap

Answer 21

Large, irregular boulders placed to slow the attack of erosion.

Question 22

What are key variables in how streams work?

Answer 22

Discharge, available setiment, gradient, and sinuosity.

Question 23

What is the relationship of discharge and load?

Answer 23

The greater the discharge, the greater the load of sediment carried.

Question 24

What factors cause a river to come out of equilibrium?

Answer 24

Too much discharge or too much load.

Question 25

What are lakes, in a geologic sense?

Answer 25

Temporary features that streams are striving to eliminate.

Question 26

Florence, Italy, 1333 and 1966

Answer 26

River Arno flooded 633 years after it flooded in 1333, to the day. Flowed through the city at 6.2 m depth. Burst open drums of oil.

Question 27

What is the relationship between the size and recurrence time of a flood?

Answer 27

The larger the floods, the longer the recurrence times between each.

Question 28

What phenomena unleash killer floods?

Answer 28

A local thundercloud can form and unleash a flash flood in just a few hours, abundant rainfall lasting for days can cause regional floods that last for weeks, the storm surges of tropical cyclones flood the coasts, the breakup of winter ice on rivers can pile up and temporarily block the water flow, hot weather can cause rapid melting of snow, short-lived natural dams fail and unleash floods, human-built dams and levees fail.

Question 29

Distinguish between flash floods and regional floods.

Answer 29

A typical flash flood results when rain falls intensely for hours in a small area. Regional floods occur when lots of rain falls over a large area for days or weeks.

Question 30

Most flood related deaths are caused by what type of flood?

Answer 30

Flash flood

Question 31

In the U.S., how much of the land is floodplain? This land is home to how much of the population?

Answer 31

2.5%, 6.5%

Question 32

What has become a significant problem posed by the Mississippi River’s desire to change course?

Answer 32

The river has long wanted to avulse toward the Atchafalaya River, but is being forced to continue down the Mississippi by the U.S. Army Corps of Engineers. They want the river to continue flowing through the major cities of Baton Rouge and New Orleans.

Question 33

Action stage

Answer 33

Water begins overtopping the banks.

Question 34

Minor flood stage

Answer 34

Roads, parks, and yards may be covered by water.

Question 35

Moderate flood stage

Answer 35

Building inundation occurs; roads are closed and evacuations may be necessary.

Question 36

Major flood stage

Answer 36

Buildings may be completely submerged; lives are threatened and large-scale evacuations may be necessary.

Question 37

Slow motion disaster

Answer 37

Insidious disasters

Question 38

Name some structural responses to floods.

Answer 38

Dams, levees, engineering projects, and sandbagging

Question 39

Name some nonstructural responses to floods.

Answer 39

More accurate flood forecasting, zoning and land-use policies, insurance programs, evacuation planning, and education.

Question 40

What is channelization? What problems does it pose?

Answer 40

It is the attempt to control floodwaters by clearing channels of debris, and making them deeper, wider, and straighter. This creates huge discharge and destroys the habitat.

Question 41

How are desert floods different from normal floods?

Answer 41

Most of the damage of desert floods is due to bank erosion, not inundation.

Question 42

What is the largest-scale problem posed by ice-dam failure floods?

Answer 42

The discharge of cold, low-salinity glacial meltwater could change the circulation of deep water through the world ocean, changing global climate.