REVIEW QUESTIONS FOR FINAL EXAM

Note: correct answers to multiple choice questions are underlined

1.  Which of the following conditions would lead to the most soil erosion?

      a.  Heavy rainfall (from a single storm) in an area of low average annual rainfall.
      b.  Steep slopes in a tropical rainforest.
      c.  An agricultural region where soil conservation practices are implemented.
      d.  An area that has been urbanized for several decades or more.
      e.  All of the above would produce roughly the same amount of erosion. 

2.  Why do agricultural areas often experience the greatest amount of soil erosion?

      a.  Because they typically occur in areas of high rainfall.
      b.  Because they typically occur in areas of moderately steep slopes.
      c.  Because farming typically involves plowing the soil to plant seeds.
      d.  Because farmers typically remove trees from their fields.
      e.  Because farms are typically located near streams. 

3.  What does the term "sediment yield" refer to?

      a.  The amount of sediment eroded from hill slopes by water.  
      b.  The amount of sediment eroded from the land by wind.
      c.  The amount of sediment eroded by either water or wind.
      d.  The amount of sediment leaving a drainage basin in a stream.
      e.  None of the above is true.

4.  Why is sediment yield often less than soil erosion in a given drainage basin?

     a.  Because streams usually cannot carry all of the sediment that is eroded.
     b.  Because sediment yield is totally unrelated to soil erosion.
     c.  Because streams naturally evolve towards a graded condition.
     d.  Because a stream's bed load usually exceeds its suspended load.
     e.  Because most drainage basins occur in areas of high rainfall. 

5.  Why were soil conservation efforts in Coon Creek Valley, Wisconsin not
     successful in reducing Coon Creek's sediment yield?

     a.  Because the soil conservation efforts were ineffective.
     b.  Because Coon Creek adjusted to the reduced soil erosion by eroding
          sediments from the valley bottom. 
     c.  Because the soil conservation efforts were not implemented throughout
          the entire drainage basin. 
     d.  This mystery has never been solved.
     e.  Because sediment yield is not related to soil erosion.

6.  Why might a river's suspended-sediment yield not be a good measure of the
     total soil erosion in that river's drainage basin?  

     a.  Because some suspended sediment might come from other sources.
     b.  Because the river might not be able to carry all of the soil that is eroded.
     c.  Because the river  might not be graded at the time when the suspended-
          sediment yield measurements are made.
     d.  All of the above are possible. 
     e.  None of the above. 

7.  What is a drainage basin?

      The total land area that contributes runoff to a given stream.

8.  What characteristics of a drainage basin affect its response to rainfall?  In
     particular, what characteristics make a drainage basin inefficient? 

     Characteristics that make drainage basins inefficient are permeable soils,
     flat topography, rectangular drainage patterns, and forests.

9.  What effect does urbanization have on flood recurrence intervals?

      Urbanization causes floods to occur more frequently.  Therefore, it tends
      to reduce the recurrence interval of any given flood. 

10.  What does lag time refer to in the context of flooding? 

       Lag time is the time between the rainstorm and the peak streamflow.

11.  What are the negative consequences to the various flood-control measures?

        a. Floodwalls cause rivers to deposit sediments within their channels afer
            a flood; thereby causing the river level to slowly rise through time.

        b. Stream channelization causes more severe flooding downstream of the
            channelized section.  Channelized streams have greater slopes and will
            therefore erode and meander to re-establish their graded condition.

        c. Flood control dams trap sediments; therefore the reservoirs need to be  
            dredged periodically to maintain capacity.  The removal of sediments by
            a dam will also cause downstream erosion by the stream.

12.  Regulatory floodplains:

       a.  are typically defined based on the 100-year flood elevation.
       b.  are never flooded more than once in a 100-year period.
       c.  have a 1% chance of being flooded in any 100-year period.
       d.  All of the above are true.
       e.  None of the above are true.

13.  Channelization and flood-control dams:

       a.  disrupt a stream's graded condition.  
       b.  require periodic maintenance to be effective flood-control measures.
       c.  have been widely used to control flooding along the Mississippi River.
       d.  All of the above are true.
       e.  None of the above are true.

14.  True or false: rivers tend to naturally meander back and forth across their floodplains. 

        True: this helps create the wide valley in which floodplains develop.

15.  Which of the following slope movements would be most likely to occur as a result of adding weight to the
       "head" of the slope? 

       a)  A slump.
       b)  A block glide.
       c)  Soil creep.
       d)  A debris avalanche.
       e)  A mudflow.  

16.  Under what conditions could the addition of weight to a slope trigger a block glide? 

       a)  When the slope is composed of unconsolidated material.
       b)  When there is cohesion present along the potential slip plane.
       c)  When the potential slip plane is oriented away from the valley.
       d)  When the slope has just experienced a fire.
       e)  None of the above.  

17.  Which of the following slope movements could be triggered by heavy rainfall or snowmelt? 

       a)  A slump.
       b)  A block glide.
       c)  A mudflow.
       d)  A debris avalanche.
       e)  All of the above.  

18.  True or false:  removing vegetation (and thus weight) from a slope increases its stability.

        False: vegetation helps prevent soil erosion and debris flows.

19.  The Portuguese Bend Landslide:

        a)  was, technically speaking, not a true landslide.
        b)  occurred as a result of above-average rainfall.
        c)  was proven to be the result of road construction.
        d)  might have occurred even if Crenshaw Blvd. had not been built.
        e)  occurred as a result of below-average rainfall.

20.  How does a debris flow differ from soil erosion by water?

        a)  They differ primarily by the amount of water involved in the process.
        b)  Soil is not considered "debris".
        c)  Soil erosion is much faster process than is a debris flow.
        d)  Debris flows only occur on ash-covered volcanic slopes.
        e)  Actually, there is no difference between these processes.

21.  Soil creep:

        a)  occurs only on moderate to steep slopes.
        b)  is important mostly because of the damage it causes to human structures.
        c)  creates "tracks" or "chutes" along hill slopes.
        d)  is most effective in desert environments.
        e)  All of the above are true statements.

22.  Debris flows:

        a)  can be triggered by periods snowmelt in the spring.
        b)  typically have a threshold relationship with rainfall duration.
        c)  often occur after forest fires move through mountainous areas.
        d)  are more likely to occur along slopes that have little or no vegetation.
        e)  All of the above are true statements.

23.  True or false: all sinkholes form suddenly, without warning.

        False: solution and subsidence sinkholes form gradually.

24.  Collapse sinkholes:

        a)  can form naturally as subsurface cavities grow larger through time. 
        b)  can form as a result of human activities, such as groundwater withdrawal.
        c)  can form naturally during periods of below-average rainfall.
        d)  all of the above are true.

 25.  What factors could influence the likelihood of sinkhole collapse occurring in an area underlain by soluble
        bedrock?

        a)  The depth to a subsurface cavity. 
        b)  The type of material present at the land surface.
        c)  Natural variations in rainfall.
        d)  Groundwater withdrawal for human use.
        e)  All of the above.

26.  What aspect of a wave form influences its erosive power?

        a)  Its wave length. 
        b)  Its wave height.
        c)  Its wave base.
        d)  All of the above.
        e)  None of the above is true.

27.  Why do tsunamis grow so large as they approach the shoreline?

       Because they have very deep wave bases that cause them to touch the ocean
       bottom and begin breaking far offshore.

28.  True or false:  wave refraction causes a concentration of energy in bays.

       False: energy is concentrated on the headlands.

29.  True or false:  the distance from a wave crest to its trough is known as the wave base.

        False: this is the wave height.

30. Which of the following human activities can affect the rate of coastal erosion? 

       a)  Pumping groundwater from a confined aquifer near the coast.
       b)  Constructing a dam along a river that leads to the ocean.
       c)  Employing soil conservation practices in a watershed adjacent to the coast.
       d)  All of the above.
       e)  None of the above.

31.  Why do engineering structures not provide a permanent solution to coastal erosion?

        Because they do not address the underlying problem, which is rising sea
        level (for marine coasts) and often a lack of coastal sediment..

32.  At which of the following locations would you expect coastal erosion? 

       a)  The "upcurrent" side of a groin, jetty or breakwater.
       b)  An area of shoreline with a negative sediment budget.
       c)  At the mouth of a river that empties into a bay.
       d)  All of the above.
       e)  None of the above.