Which type of dam is built to control downstream flooding?
a. flood-control dam
b. wing dam
c. hydroelectric dam
d. spillway dam
e. all types of dams
Question 2Which is NOT an unintended consequence of building an artificial levee?
a. It causes the stream to flow faster.
b. It raises the water level during flooding.
c. It causes more upstream flooding.
d. It causes more downstream flooding.
e. It protects towns from flooding for a time.
Question 3How does failure of an artificial levee differ from failure of a natural levee?
a. The water spills slowly over the levee into its floodplain, dropping coarser particles next to the main channel.
b. The water flows faster, and the areas next to the levee are commonly buried under sand and gravel.
c. The water flows slowly, depositing valuable topsoil in the floodplain.
d. The water flows at the same speed as the river, limiting erosion.
e. There is no difference between failure of an artificial and a natural levee.
Question 4Which is NOT a common method of levee failure?
a. seepage
b. bank erosion
c. interweaving
d. slumps into the channel
e. piping
Question 5When a large flood first breaches a levee, what are the characteristics of the water crossing the breach?
a. relatively clear, highly eroding
b. relatively cloudy, highly eroding
c. relatively clear but not prone to strong erosion
d. relatively cloudy but not prone to strong erosion
e. about the same average sediment load as the flooding stream
Question 6What is/are the best material(s) for building a levee?
a. locally available material from the floodplain
b. sand and mud
c. coarse gravel
d. clay
e. crushed rock
Question 7Why is living on a floodplain behind a levee safe from flooding?
a. Levees are rarely overtopped.
b. Water cannot seep under levees to flood the floodplain.
c. Levee banks are rarely eroded enough to fail.
d. Once a levee is built high enough to contain a 100-year flood, it will never flood.
e. Actually, 100-year flood levels often continue to get higher with time.
Question 8How does a bridge promote erosion in a channel?
a. The bridge pilings interfere with the water flow, causing additional sediments to be deposited.
b. The water velocity decreases, due to restricted flow over the floodplain.
c. The water velocity increases, due to restricted flow over the floodplain.
d. The channel height decreases, and large particles fall out, creating more surfaces for erosion to occur.
e. A bridge does not promote erosion.
Question 9How does streambed mining affect a stream?
a. It increases erosion in the downstream channel.
b. It carries greater sediment load downstream.
c. It slows stream water velocity.
d. It increases groundwater supplies away from the stream.
e. It steepens the channel gradient downstream.
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