2. What characteristics of a drainage basin cause it to have an "efficient" response to rainfall?
Choice 1 Steep topography.
 Choice 2 Permeable soils.
 Choice 3 A rectangular drainage pattern.
 Choice 4 The occurrence of numerous wetlands.

REVIEW QUESTIONS FOR FLOODS AND FLOOD CONTROL

Instructions: underlined and colored text is linked to an image that will help explain the concept in question. These images are popup windows that should be closed when you are done. To choose an answer, click the mouse on a blue button. A popup message will appear to indicate whether your choice is correct or not. Sometimes a popup message will also take you to another image when you click on OK. To escape these images, you must close the popup window.

 

 

 

 

 

 

 

 

 

1. What is a drainage basin?

Choice 1 A drainage basin is the total land area that contributes runoff to a given stream.
 Choice 2 A drainage basin is a low area that occurs adjacent to any given stream.
 Choice 3 A drainage basin is an artificial pond that is constructed to hold runoff during a storm.
 Choice 4 A drainage basin is a low area to which all streams in a given region drain.
Choice 4 A drainage basin is none of the above.

 

 

 

 

 

 

 

 

 

 

3. What does "lag time" refer to in the context of flooding?
Choice 1 The time required to clean up an area following a flood.
 Choice 2 The time it takes for emergency officials to provide relief to residents of a flood-stricken area.
 Choice 3 The time it takes for streamflow to travel from the drainage divide to the mouth of the stream.
 Choice 4 The time between rainfall and peak streamflow.


 

4. What effect does urbanization have on rainfall-runoff relationships?
Choice 1 Impermeable surfaces tend to inhibit infiltration and thus increase peak flood discharges.
 Choice 2 Storm sewers tend to route runoff to streams more quickly and thus reduce the lag times.
 Choice 3 Urbanization tends to decrease the recurrence interval of any given flood.
 Choice 4 Urbanization tends to increase the frequency of any given flood.
 Choice 4 All of the above are correct.

 

 

 

 

5. Regulatory floodplains:
Choice 1 are typically defined based on the 100-year flood elevation.
 Choice 2 are never flooded more than once in a 100-year period.
 Choice 3 have a 1% chance of being flooded in any 100-year period.
 Choice 4 have a 100% chance of being flooded in any 100-year period.
 Choice 4 None of the above is true.

 

 

 

6. Channelization and flood-control dams:
Choice 1 have been widely used to reduce the risk of flooding because they require little or maintenance.
Choice 2 each disrupt a stream's natural, graded condition, causing the stream to adjust its slope in some fashion.
 Choice 3 are less disruptive to streams than are river diversions.
 Choice 4 All of the above are true.
 Choice 4 None of the above is true.

 

7. Floodwalls:
Choice 1 are widely used because they prevent floods without disrupting a stream's natural, graded condition.
 Choice 2 are the best (least disruptive) flood-control measure because they simply enhance a stream's natural levees.
 Choice 3 can eventually lead to a situation where a river flows above the level of its floodplain even during normal flow.
 Choice 4 All of the above are true.