Lab09_Fluvial
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Bunker Hill Community College *
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101
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Geography
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May 14, 2024
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docx
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Laboratory 9: Fluvial Landforms
Description:
This lab gives you an opportunity to examine landforms associated with fluvial (river-related) erosion and deposition. On a global basis, rivers are the most significant agent shaping earth’s surface features. Rivers erode sediment from their bed and banks, transport sediment as bedload, suspended load and dissolved load, and deposit sediment on floodplains, alluvial fans, and deltas.
By examining topographic maps and aerial photographs of rivers you will be able to identify specific shapes of fluvial landforms. Landform morphology will also help interpret the dominant geomorphic processes active on the landscape.
Key Terms:
Fluvial
Meandering
Braided
Floodplain
Lateral accretion deposits
Vertical accretion deposits Levee
Backswamp
Oxbow lake
Point bar
Meander scar
Alluvial fan
Bajada
Basin floor
Fault scarp
Exercise 9-A: Floodplains
Examine the map and aerial photograph of the Red River near Campti, Louisiana from
Atlas of Landforms
(located with the Module 3
Lab09 module in Canvas
).
1.
Is the Red River a meandering or braided river? How do you know?
2.
Is Smith Island a true island? Why or why not?
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3.
“Old River” surrounds most of Smith Island. What kind of landform is this? How is it related to the Red River? 4.
Notice the cartographic symbol used on the inside of meander bends. What does this symbol represent? What is the name of this deposit? Use Google Earth (earth.google.com) to find Campti, Louisiana. Zoom out a little to see the two oxbow lakes located just east of Campti (see photo below for reference). Make sure you have reviewed the lab lecture slides that accompanies Lab09. 5.
Measure the radius of curvature in miles (distance from center of oxbow lake to outer bank of the lake at
Old River) of the oxbow lake around Smith Island on the Red River. Average these values and convert the average values to units of miles. Show all calculations below. The radius of curvature for two additional oxbow lakes (A and B) along the Red River has been calculated for you.
Old River
Oxbow Lake A (Miles)
Oxbow Lake B (Miles)
Measurement 1
0.5
0.4
Measurement 2
0.68
0.87
Measurement 3
0.58
0.75
Measurement 4
0.45
0.48
Measurement 5
0.44
0.74
Average (Miles)
0.53
0.65
Average Radius of Curvature for oxbow lakes on the Red River: ________________________________
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6. If you were to repeat this process for the Mississippi River, you would find that the average radius of
curvature for its oxbow lakes is larger than those of the Red River. Why would you say this is the case?
Exercise 9-B: Alluvial Fans
Examine the map of Kokand, Uzbekistan
(located with the
Module 3
Lab09 module in Canvas).
1.
What type of stream flows north out of the mountains at B? What physical and/or watershed processes are responsible for creating this landform (view from above; i.e., what type of stream is it)?
2.
Examine the contour intervals near the head of the larger fan near Kokand. Do these indicate that the fan
is building (aggrading) or eroding (incising)? (Hint: think about what happens when a stream erodes into a land surface) 3.
What do you know about the climate in this region? (Note: If you don’t know anything about the climate, you should consult an atlas/look it up.)
4.
Considering your knowledge of Kokand’s climate, in what way do you think humans have modified the natural environment near Kokand to support their use of the land? 11-3
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