Download rivers channel shape lab

Name ________________________
Period # _______
Date _____________
Lab#: ____: River Channel Cross-Section Shapes
Purpose: In this lab, you will use data to draw and analyze a cross-section (also termed, “a profile”,
as you remember buckaroos) of a river channel at different locations along its path.
Introduction: The varying velocity of water in a river directly and dramatically affects the shape of its
channel. Generally, faster-flowing water erodes a deeper channel creating a cut bank, while slowermoving water erodes less – and even deposits sediments – creating a point bar in the channel.
Background: Review Table 1 showing data for three locations across a mature or old river. Five
sites are listed along each location’s cross section, and depths were measured and recorded at each
site at locations A and B. The sites where the depth measurements were measured are shown on
the river channel diagram – see transect A-A’ and B-B’. As a reminder, keep in mind that the river
channel diagram is a top view (or map view) perspective, and therefore, flow is generally
perpendicular to the transect A-A’, B-B’, and C-C’.
Procedure:
1. Plot the depth data shown on Table 1 on the A-A’ and B-B’ graphs. Connect the points from
shoreline to shoreline to show a smooth cross-sectional shape of the river channel at each site for
transect A-A’ and B-B’. Be sure that your profile extends from shoreline to shoreline!!!
2. In Table 1, record what you infer the depths would be for C-C’.
3. Using the data from Step #2 above, draw a cross-sectional view of what you think the channel
shape would be along transect C-C’. Be sure that your profile extends from shoreline to shoreline!!!
Please take careful notice of exactly where the numbers are on the overhead diagram of the river
when answering the questions. Also, remember that if you’re measuring the velocity of the river, you
must be in the WATER to measure it…
Page 1
RIVER CHANNEL DIAGRAM
TABLE 1
LOCATION
A – A’
SITE
DEPTH
(M)
SITE
DEPTH
(M)
1
2.0
1
2.0
1
2
8.0
2
12.0
2
3
12.5
3
17.0
4
15.0
4
12.0
4
5
16.0
5
2.0
5
LOCATION
B – B’
Page 2
LOCATION
C – C’
SITE
3
DEPTH
(M)
CROSS-SECTION A – A’
CROSS-SECTION B – B’
Page 3
CROSS-SECTION C – C’
Analysis Questions
(Important Reminder: Full sentences are required. For example, the answer to Question #1 could start, “The
water velocity along A-A’ is greatest…”)
1. After reviewing cross-section A-A’, state the site number in the channel where the river’s velocity is greatest
and use evidence from the diagram to support your claim.
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2. State the site number in the channel along cross-section A-A’ where the river’s velocity is the slowest and
use evidence from the diagram to support your claim.
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3. Review cross-section B-B’. Determine the fastest and slowest sites:
Fastest: ______________
Slowest: ______________
4. Review cross-section C-C’. Determine the fastest and slowest sites:
Fastest: ______________
Slowest: ______________
5. At which site would you expect to find the greatest deposition along cross-section A-A’? ____________
6. Explain your answer to Question #5: ________________________________________________________
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7. At which site would you expect to find the greatest erosion along cross-section A-A’? _______________
8. Explain your answer to Question #7: ________________________________________________________
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For Questions #9 and #10 below be sure to use the terms in italics and bold exactly as shown when
discussing the relationships between variables. Additionally, all scientific reasoning statements express the
independent variable (the “initiating” or the “source” of the change) first before describing changes in resulting
dependent variable(s) within a system. (Hint: The river variables shown below are in this order to help you 😊
%.)
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#
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9. Write a clear and succinct statement summarizing the relationship between river velocity and potential
sediment load that a river has the potential to carry/transport within its channel:
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10. Based on your response to question #9, write a clear and succinct statement summarizing the relationship
between river velocity and the resulting channel depth in a river:
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