Practice Questions for Lecture 13 – 14
Streams and Groundwater
Geology 1200
KEY
Use these questions to test your knowledge of Lecture 13 - 14.
A. Short answer:
1. Each year, erosion is responsible for the removal of an estimated 3.5
million metric tons of rock from the continents.
2. Hydraulic lifting occurs as a turbulent stream flows through fractures
in rock .
3. Abrasion and hydraulic lifting are more (efficient, powerful, energetic)
in fast, turbulent streams than in slow ones.
4. A graded stream responds instantaneously to any change in sediment
load or discharge in such a way as to establish a new graded state.
5. Every stream carries water from a watershed that is separated from
other watersheds by a drainage divide.
6. In a curved section of a stream channel, the fastest water is near the
outside of the curve.
7. In a straight section of a stream channel, the fastest water is in the
center of the channel just below the surface.
8. In a curved section of a stream channel, the slowest water is near the
inside of the curve.
9. In a point bar deposit, the lowermost sediments are course particles
from the stream bed.
B. Match the Terms.
1. abrasion__m___
a. heavy sediment load
2. point bar deposit__i__
3. saltation__l__
b. steep stream meets broad flat valley
c. water table dropped.
4. floodplain __j__
d. characteristic of karst
5. gradient __o_
e. erosion and deposition equilibrium
6. alluvial fan __b__
f. ability to carry sediment
7. braided stream __a___
g. flow between pores
8. capacity__f___
h. volume space between grains
9. graded stream___e__
i. meandering stream
10. base level__n__
j. submerged during floods
11. Porosity __h__
k. groundwater recharge
12. Permeability __g__
l. bouncing
13. Disappearing stream __d__ m. scrape stationary rocks
14. Collapse sinkhole __c__
n. lowest possible erosion
15. Infiltration __k__
o. slope of streambeds
16. Competence ___p___
p. largest particle carried.
C. True or False? Circle the correct answer. Some of these are from your reading.
1. A stream’s base level is the lowest level to which a stream can erode
its channel. True or False?
2. A graded stream is one in which an equilibrium has been reached so
that there is little net erosion or deposition. True or False?
3. After a sudden increase in sediment load in one area, a stream’s local
gradient increases, as does stream velocity. True or False?
4. During a flood, a stream’s power to erode its channel increases
dramatically. The increase in erosional power is proportional to the
square of the increase in velocity. True or False?
5. Stream piracy occurs when one stream captures the headwaters of
another stream on the opposite side of a drainage divide. True or False?
6. The stream that erodes through its divide to capture the other slope
drainage does so because of its steeper slope, greater discharge, and less
resistant streambed rocks. True or False?
7. Braided streams are caused by an exceptionally low sediment load.
True or False? In particular, braided streams have very high bed load and
intermittent flow.
8. Streams develop meanders because erosion occurs on the outside
(cutbank) of curves, where water velocity is highest, while bar deposition
occurs on the inside of curves, where water velocity is lowest. The result
is greater channel curvature. True or False?
9. Alluvial fans are formed on low-land plains, while deltas are formed in
a standing body of water. True or False?
10. Waterfalls tend to migrate downstream and become larger as erosion
wears away their edge. True or False?
11. Streams that disappear into sinkholes are a sure sign of karst land.
True or False?
12. Most caves are formed by subsurface dissolution of granite. True or
False?
13. Grading (leveling) of steep slopes can enhance groundwater recharge
because such a measure reduces the runoff of rainwater. True or False?
14. A perched water table is a water table found on top of a local
impermeable layer lying above the zone of saturation. True or False?
15. A water table’s configuration (its underground depth) is usually
random and unpredictable. True or False?
16. The greatest infiltration of surface waters would be on steep slopes.
True or False?
17. Porous, unconsolidated clays encourage infiltration better than
fractured or jointed bedrock. True or False?
D. Multiple choice:
1) Which of the following statements about stream transport is TRUE?
a) A stream’s competence is a measure of the diameter of the largest
particle that the stream can transport.
b) A stream’s competence is proportionate to the square of its velocity.
c) A stream’s capacity is a measure of the maximum quantity of
sediment the stream can transport.
d) All of the above
2) Which of the following statements concerning a stream’s sediment load
is NOT true?
(a) The brown color in muddy rivers is caused by an unusually high
dissolved load. Note: The dissolved load is colorless. The suspended
load is often brown.
(b) Large stones that cannot be carried within a stream’s suspended load
can sometimes be transported by traction in the stream’s bed load.
(c) Fine particles of clay are likely to be transported as part of the
suspended load.
(d) Both flat and low-density particles tend to remain within the suspended
load.
3) The volume of a stream’s dissolved load is dependent on all of the
following factors EXCEPT:
(a) climate.
(b) stream velocity.
(c) bedrock composition and acidity of the water.
(d) topography.
4) Braided streams with, large amounts of very coarse bed-load sediments,
deposit what bedform?
(a) Point bars.
(b) Mid-channel bars.
(c) Levees.
5) Accumulations of gold, platinum, or silver would most likely be found:
(a) on the outside of meander curves, where the high velocity of the water
has embedded them in the banks.
(b) in point bars on the inside of meander curves, and near boulders, where
stream velocity is the slowest.
(c) distributed evenly throughout the stream bed.
6) Natural levees result when:
(a) streams flood their banks and deposit sediment directly on top of the
banks.
(b) streams erode downward in their channel, leaving their banks higher
relative to the surface of the stream.
(c) hard, erosion-resistant rocks become part of a stream’s banks.
(d) smaller streams flow parallel to a main stream and deposit material on
the stream bank.
7) The highest point along a meandering stream floodplain would be:
(a) the channel bank.
(b) the levees.
(c) the channel gravels
(d) the point bar deposits.
8) The primary difference between a delta and an alluvial fan is that:
(a) alluvial fans are erosional features, whereas deltas are depositional
features.
(b) alluvial fans result from deposition into inland lakes, while deltas
result from deposition into the ocean.
(c) alluvial fans form at the source of a stream and deltas form at the
mouth of a stream.
(d) alluvial fans are formed on low-land plains, while deltas are formed in
a standing body of water.
9) Which of the following statements about deltas is NOT true?
(a) The material that constitutes a delta is called alluvium.
(b) Foreset beds are sediments deposited the farthest from the mouth of the
stream.
(c) Bottomset beds are sediments deposited in horizontal layers away from
the mouth of the stream.
(d) Topset beds are sediments deposited in horizontal layers on the surface
of the delta near the mouth of the stream.
10) The highest point along a meandering stream floodplain would be:
(a) the channel bank.
(b) the levees. Identical to # 7
(c) the gravel load
(d) the point bar deposits.
11) Which of the following conditions is most favorable for delta
formation?
(a) Where waves and currents immediately sweep away most of the river’s
delivered sediments.
(b) Where powerful storm waves carry all of the river’s delivered
sediment.
(c) Where a large sediment load is delivered to quiet coastal waters.
(d) Where a small sediment load is delivered along the river’s short path to
quiet coastal waters.
12) A large cone of depression is least likely to develop when:
(a) a large amount of water is removed from an aquifer.
(b) there is little precipitation in an area.
(c) the aquifer has minimum permeability.
(d) recharge exceeds discharge.
E. Short Answer
1.
List and describe the parts of a stream system.
2.
How does stream velocity differ in different parts of a stream
channel? Fast in steep uplands, slower on plain.
3. Explain porosity and permeability, and define an aquifer.
Porosity: space between grains
Permeability: ability of water to flow between grains
Aquifer: sediment with high permeability, and containing water.