Reading Assessment for Chapter 6
Which statement is FALSE about the effects that floods can have?
Flooding has no positive effects; it is always bad for human interests.
Which of the following natural hazards is the number 1 disaster in the United States in terms of lives lost over the past century?
Floods
Which of the following has the LEAST effect on flood damage? Assume that a moderate amount of development is available for flood damage.
Geographic region
What is the stage of a river?
Height of water that is flowing
Which of the following will tend to REDUCE the size of a river flood?
High rate at which the precipitation soaks into the ground
Which homes built on the floodplain are most likely to sustain the greatest damage?
Houses within the 20 year floodplain.
In which of the following environments are flash floods LEAST common?
Humid environments with large meandering rivers
If you were running water through a hose, how would you increase the discharge of water coming from the hose?
Turn up the water at the faucet.
Which of the following is NOT an example of how urbanization influences a river or stream?
Urbanization increases rainstorm frequency and therefore increases the frequency of floods.
What is the role of a drainage basin?
A drainage basin is the area drained by a river and all of its tributaries.
What is the floodplain?
A flat area next to the river carved out by the rivers
What would the longitudinal profile of a river flowing from a gentle valley into an ocean look like?
A gently downward sloping line
In which of the following cases would you expect the LEAST amount of flooding due to a rainstorm? Assume all areas receive similar amounts of rainfall in the rainstorm and there are no flood control measures in any of the areas.
A long duration rainstorm falling on an area that consists of forest, grasslands, and no human development.
What is avulsion?
A river shifts its position after a flood.
Which of the following loads are most likely to consist of heavy rocks and boulders?
Bed load
Choose the best answer. Which would increase during a flood, discharge or velocity?
Both discharge and velocity will increase because there is more water flowing and it is flowing faster.
What two parameters are plotted in a hydrograph?
Discharge vs. time
If you dip a glass of water into a river and passed the water through a very fine sieve that blocked all sediment grains from passing through, what will you be left with?
Dissolved load
How would the hydrograph of a large rainstorm change after urbanization of an area?
The peak of the hydrograph would become higher and narrower.
During a flood, the safest place to be is behind a levee or floodwall.
False
Flash floods are most common on the floodplains of large meandering rivers.
False
Flash floods are usually of short duration and therefore not very dangerous.
False
Hydrographs are used to show the amount of water in the hydrologic cycle.
False
If the discharge of a river is constant and the river channel suddenly widens, then the velocity of the river will decrease.
False
If you live on the 100 year floodplain, it means that you are guaranteed to have one large flood once every 100 years.
False
Living near a dam is very safe because you will never have to worry about flooding.
False
Paving over land decreases the amount of flooding because water can't soak into the soil.
False
The longitudinal profile of most streams is an upwardly curving line.
False
What distinguishes flash floods from downstream floods?
Flash floods occur in the upper part of a drainage basin, downstream floods occur in the lower part of a drainage basin.
How would a river in an area changed from forest to farmland react to changes?
Increased amounts of sediment would increase the gradient of the stream.
Which of the following adverse effects of natural hazards is NOT associated with flooding?
Land upheaval
Which of the following are things that you should NOT do in preparing for a flood?
Make a flood kit and place it in your basement.
What should you do during a flood?
Move to higher ground away from the river.
Does channelization of a stream completely prevent flooding?
No. Nothing can prevent flooding.
Does it have to be raining for a river to flood?
No. Rivers can flood after rain has stopped and tributaries have flowed into bigger streams.
Where on a river would you most likely find point bars?
On the inside of a bend
Where does a meandering river run the fastest?
On the outside of a bend
Where on a river would you most likely find cutbanks and why?
On the outside of a bend because that is where the river erodes most.
What is the greatest hazard to people in a flash flood?
People driving into floods and being carried away
Which of the following is NOT an example of a base level for a river?
Rapids
Which rivers have the highest gradient?
Rivers moving down mountains
Which of the following loads would make a river appear murky or dirty?
Suspended load
What is a hydrograph NOT able to tell you about a river?
The amount of rainfall an area receives
If you are standing in the middle of a river and look at either side, you might see tall earthen hills. What are they and what do they do?
They are levees and they hold in floodwaters.
What happens to rivers when they reach their base level?
They often form alluvial fans or deltas.
Which of the following is NOT information that can be obtained by calculation of a recurrence interval for a flood?
Time of day when the maximum floodwaters will occur during a flood event
A narrow river usually runs faster than a wider one.
True
A river in flood stage can erode and transport more sediment than the same river in normal flow.
True
After a flood, you should be sure to wash anything that has been in touch with river water.
True
An alluvial fan can be found at the base level of rivers.
True
At a river meander, erosion occurs on the outside part of the bend, and deposition occurs on the inside part of the bend.
True
Channelization is one of the more drastic solutions to flooding because it can cause the draining of wetlands, which can have a negative impact on the wildlife.
True
Construction of levees can actually make floods worse in areas upstream and downstream from the construction.
True
Insurance and building codes are two important ways that the government can protect property from disaster in a flood.
True
One of the benefits of flooding is deposition of fertile soil.
True
Rivers normally stay in a state of dynamic equilibrium between their flow velocity, their gradient, and their cross-sectional area.
True
The bed load of a stream is involves the largest grains in the stream.
True
The gradient of streams is higher at headwaters than at the mouth of a river.
True
Tributaries are smaller streams which drain into larger rivers.
True
In which cycle do rivers NOT play an important role?
tectonic cycle
