Homework Questions for Lecture 11-12
ES 1000
Use these questions to test your knowledge of Lecture 11-12 on Streams and
Groundwater
A. Short answer:
1. Hydraulic lifting occurs as a turbulent stream flows through
fractures in _________.
2. Abrasion and hydraulic lifting are more _________ in fast streams
than in slow ones.
3. A graded stream responds instantaneously to any change in
_________ load or discharge in such a way as to establish a new
graded state.
4. Every stream carries water from a watershed that is separated from
other watersheds by a drainage ________.
5. In a curved section of a stream channel, the fastest water is near the
_______ of the curve.
6. In a straight section of a stream channel, the fastest water is in the
______ of the channel just below the surface.
B. Match the Terms.
1. abrasion_____
a. heavy sediment load
2. point bar deposit____
b. steep stream meets broad flat valley
3. saltation____
c. water table dropped.
4. floodplain ____
d. characteristic of karst
5. gradient ____
e. erosion and deposition equilibrium
6. alluvial fan _____
f. ability to carry sediment
7. braided stream _____
g. ability to move water between pores
8. capacity______
h. volume space between grains
9. graded stream______
i. meandering stream
10. base level_____
j. submerged during floods
11. Porosity _____
k. groundwater recharge
12. Permeability _____
l. bouncing
13. Disappearing stream ___
m. scrape stationary rocks
14. Collapse sinkhole _____
n. lowest possible erosion
15. Infiltration ______
o. slope of streambeds
16. Competence ______
p. largest particle carried
C. True or False? Circle the correct answer.
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 stream bank collapses, partially blocking a channel with
sediment, a stream’s velocity increases there. True or False?
4. During a flood, a stream’s power to erode its channel increases
dramatically. The erosional power is proportional to the square of the
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 high sediment load.
True or False?
8. Streams develop meanders because something disturbs a straight
channel. Uneven erosion starts when flow is deflected to one side.
Erosion continues 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 upstream and become smaller as erosion
wears away a resistant rock forming the local base level. True or False?
11. Streams disappearing into sinkholes identifies karst land. True or
False?
12. Most caves are formed by subsurface dissolution of limestone. True
or False?
13. Grading steep slopes (terracing them so that large areas are level) can
enhance groundwater recharge because such a measure reduces the runoff
from precipitation. 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 gentle 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.
(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) Braided streams with large amounts of very coarse bed-load sediments
deposit what bedform?
(a) Point bars.
(b) Mid-channel bars.
(c) Levees.
4) 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.
5) The highest point along a meandering stream would be:
a) the channel bottom.
b) the levees.
c) the gravel bedload
d) the point bar.
6) 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.
7) 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.
8) Which of the following statements about water that contains dissolved
calcium and bicarbonate ions is NOT true?
(a) they cause the dissolution of limestone.
(b) It is considered hard water and may leave calcium carbonate
deposits in plumbing pipes.
(c) It can be carried to the sea where marine organisms use it for
building shells.
(d) It may infiltrate through unconsolidated sediments and deposit
calcite as a cementing agent.
9) Which of the following statements about limestone is NOT true?
(a) The most soluble component of limestone is the mineral calcite.
(b) Limestone dissolves most readily in pure water.
(c) Calcium and bicarbonate ions are produced as a result of the
dissolution of limestone by carbonic acid.
E. Mixed Format
1. Explain why stream water goes faster on the outside of a curve.
2. Explain why bed load is deposited on the inside of a curve
3. Explain why calcite is precipitated in caverns
F.
1. Chi-Square. Continue Reading Lecture 13, up to slide 44.
Measurements of surface water velocity are made in a curved section of a
meandering stream. A length of rope 10 meters long is prepared and is used
to mark known lengths of shore on both sides of the meander loop. Circular
bits of paper from a three-hole punch are floated, one at a time, on the
surface, and are timed along a marked length of shoreline, using a
stopwatch.
Two sets of data are collected: one for paper disks moving along 10 meters
of outer curve (cutbank side), the other along 10 meters of inner curve
(pointbar side). Every five trials are averaged, and the observations totaled
for trials that average more or less than 2 meters per second.
Velocity
0.1 - 2 m/sec
2.1 - 4 m/sec
Column Totals
Outside of
curve
17
29
46
Inside of curve
31
19
50
Row Totals
48
48
Grand Total 96
Expected frequencies = (row total x column total) / grand total. These are below:
(48x46)/96 =
23
(48x46)/96 =
23
The number of degrees of freedom n
is n = (# rows - 1) x (#columns - 1) = 1.
However, no expected value is less than
10, so no Yates correction factor is needed.
http://en.wikipedia.org/wiki/Yates%27_correction_for_continuity
(48x50)/96 =
25
(48x50)/96 =
25
Questions: Consider the claim that water moves more quickly on the outside
of the curve.
a. State the null hypothesis and, for P = 0.05
b. Test it using Chi-square. A critical values table for X2 is in your Lecture
13.