LESSON 6
PRACTICE EXERCISE
The following items will test your grasp of the material covered in this lesson. There is only one correct answer
for each item. When you complete the exercise, check your answer with the answer key that follows. If you
answer any item incorrectly, study again that part of the lesson which contains the portion involved.
1.
There are three common methods of controlling erosion on a cut slope: interceptor ditches, vegetal cover,
and-
A.
Subsurface drainage systems
B.
Headwalls
C.
Vertical wells
D.
Terracing
2.
One way of controlling erosion at the outlet of a culvert is to-
A.
Increase the slope of the pipe.
B.
Decrease the slope of the pipe.
C.
Use concrete pipe instead of CMP.
D.
Remove the headwall.
3.
Perched water and side-hill seepage are-
A.
Conditions which contribute to higher velocity
B.
Conditions causing subsurface erosion.
C.
Two methods of controlling subsurface erosion.
D.
Two stages of the hydrologic cycle.
4.
Checkdams and riprap are used to control erosion in __________.
5.
A deep ditch may help control subsurface erosion-
A.
In northern latitudes where freezing is common.
B.
Where it will not become a traffic hazard.
C.
When subsurface erosion conditions are doubtful.
D.
When you cannot afford to move the project
6.
Which subsurface drainage technique is used to help place a path across marshy areas?
A.
Vertical wells
B.
Wood culvert
C.
Sand blanket
D.
Open channels
6-11
EN5465
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