Microsoft Word - GEOG1106_Lab11_FluvialProcesses.docx
Name: Date:
Fluvial Processes and Landforms Lab Questions
***Please submit only this document at the end of the lab period***
INSTRUCTIONS: Please read the lab reader before beginning this exercise. The following lab questions will be based upon the material given in the lab reader.
Submission: Along with the regular submission, please also upload to Blackboard a PDF document from a MS Word text editor to answer questions 1, 2 and 3 (print screens of images).
Part I: Fluvial Landforms Evolution
Based on the Teton National Forest and Yellowstone National Park areas, previously uploaded in Google Earth Pro as indicated in the reader, please do the following:
1. [10] Identify and pin the following fluvial geo-forms and insert their images in your Word document.
Braided stream Oxbow lake Meander Ephemeral stream
2. [10] Select one of those features and study its evolution. Report images of the first and latest image over the time period available in your submitted document.
3. [5] Looking at the temporal evolution discuss (in less than half one page) about the changes you observe and some hypothesis that explain the observed changes for the selected feature.
4. Using the Google Earth tool and the ”FluvialProcesses_Landforms.kmz” file, search for the following locations. Use the zoom tool to be able to see well the geomorphology of the area regarding the fluvial landforms.
4.1 Mount Rainier in Washington
(a) [5] What drainage pattern is formed on Mount Rainier?
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PHYSICAL GEOGRAPHY
LABORATORY
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(b) [5] What does the drainage pattern indicate about the underlying structure and lithology of this mountain?
4.2 Lake Wales, Florida
[5] What drainage pattern dominates this area?
4.3 Strasburg, Virginia (Appalachian Mountains)
(a) [5] What channel planform presents the North Fork Shenandoah River (near Strasburg) before joining with the South Fork Shenandonah River?
(b) [5] Look at the Little Passage Creek just south-east of the North Fork Shenandonah River. What type of drainage pattern is this?
4.4 Colorado River at Granite Gorge (Rocky Mountains)
[5] What stream type is the Colorado River in Granite Gorge?
4.5 Ennis, Montana
(a) [5] What type of channel planform does the Madison River exhibit upstream of Ennis Lake?
(b) [5] What type of channel planform pattern does the Madison River exhibit downstream of Ennis Lake?
(c) [5] The Cedar Creek Alluvial Fan (and nea
y fans) represent a large deposit of material transported from the local mountains. How could these alluvial fans be affecting the Madison River channel pattern?
Part II: Streamflow calculation
5. [20] During one day in June, the Rio Grande at El Paso has the following cross sectional bathymetry and width. An USGS campaign measured the average flow velocity at each of the width intervals shown in Table 1. Please compute the Rio Grande discharge during that day.
Table 1. Rio Grande at El Paso. Streamflow measurement during a particular day in June.
Distance from left wate
edge (m)
Depth, di (m)
Velocity, v (m/s)
Average width w (m)
Average section depth, D (m)
Differential Area a=D.w
(m2)
Segmental discharge,
Q=v.a (m3/s)
0
0
0.20
5
0.40
0.20
10
0.50
0.20
15
0.50
0.30
20
0.60
0.40
25
0.70
0.50
30
1.0
1.0
35
1.0
1.0
40
0.50
0.80
45
0.40
0.60
50
0
-
-
-
-
-
Sum
Q=
6. [5] What would happen to the discharge if the flow velocity is doubled across the entire river cross-section? What would be the new discharge value?
7. [5] If you suddenly dumped sand and concrete (not recommended in real life) and reduce the flow area of the river to half, during the same time that your measured the discharge obtained in Table 1, what would happen to the flow velocity (would it increase, decrease or remain the same)?. What would happen to the total discharge (would it decrease, increase or remain the same)? Explain why.
Microsoft Word - GEOG1106-Lab10_RiverSystem_Reader.docx
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PHYSICAL GEOGRAPHY LABORATORY
Reader:
Fluvial Processes and
Landforms
Learning Outcomes: Fluvial geomorphology is the study of the origin
and evolution of landforms related to river and streamflow processes.
Geographers analyze how landforms change, or “evolve,” over time so that they
can understand how natural processes and human interactions influence
landscapes. One way to examine how features in the landscape change over time
is to compare satellite or aerial imagery of physical features such as rivers and
fluvial environments. In this lab, you will:
• Practice using the Google Earth application to look at features on ou
Earth’s surface using satellite or aerial images.
• Observe and describe how landscape features change over time.
• Explore and interpret geographic features on a map.
• Compute the mean flow of a river survey using the area-velocity method.
Materials: Pencil, lab handout, calculator, computer with Google Earth
application. Note that you are supposed to submit both a (1) hand-written lab
handout and (2) upload a PDF document to blackboard with answers to questions
1, 2 and 3 by the end of the session.
Directions
• Download Google Earth Pro to your computer workstation and open it.
• Go to File/Open and select the files “Topo” and “Teton” into Google Earth
(it has to be in this order). The Teton file area covers part of Yellowstone
National Park, Teton National Forest, and parts of three other National
Forests.
• Explore the given area using Google Earth’s imagery and the topo overlay.
Within the study area, locate the features indicated below by placing a
“Pin” on the map.
• Give the Pin the name of the feature you are identifying (Figure 1).
• Zoom-in to the identified feature and save an image of each, clicking on
File/Save/Save Image to save the image in jpg format. You will also use the
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PHYSICAL GEOGRAPHY LABORATORY
time slider to recognize time evolving patterns in the identified geoforms
(Figure 1).
Figure 1. Google Earth’s “Create Pin”, and “Time Slider” buttons.
• Insert the pictures in a MS Word document for Items 1 and 2 of the
questionnaire. Then convert this final document (with questions and 1 and 2
answered) into a PDF document to then upload into Blackboard as a part of
your lab responses before the end of the lab session.
• For questions in item 4, you can use the web-based Google Earth that
sometimes is faster than the Pro version.
Part I. River Types
As water flows, its energy is used to weather, erode, and deposit materials. Water
weathers (decomposes) and erodes (transport) materials more quickly when there
is fast, or high velocity, flow. Water deposits more materials when it does not
have enough energy to continue to move the materials, typically when there is
low velocity flow.
Another factor in erosion and deposition is the size of the materials, or sediments.
The smaller the sediment, the more likely that it will be picked up and moved by
the river. As the water velocity decreases, the amount of energy in the flow
decreases, leading to the sediment slowly settling to the bottom of the stream
ed. This process is similar to when you move on a water slide: the steep gradient
at the top results in high velocity flow, ca
ying you down the slide; at the bottom,
however, you fall into a pool with little water velocity, causing you to stop
moving. You effectively “settle out” of the water.
A river's ability to weather, erode, and deposit sediments is crucial in determining
what type of river channel will form. Other factors include: the type of bedrock in
the stream bed, the topographic gradient (i.e., the steepness of the slope of the
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PHYSICAL GEOGRAPHY LABORATORY
land), the amount of sediment moving in the water, and the volume of water
moving past a location every second (called discharge). The three types of river
channels that we will discuss in this lab are: meandering (Figs. 1 and 2), straight
(Fig. 3), and
aided (Fig. 4).
Meandering Streams
A meandering river (Fig. 2) is characterized by large, sinuous curves where the
iver has eroded or deposited material. A meandering river will deposit material
along the point bar, where water slows, and will weather and erode material
along a cut bank, where the water is fastest (Fig. 3). To imagine how water flows
in a meandering river channel, think about a time when you slid down a curved
waterslide. As you curve around a bend in the slide, you swing to the outside of
the bend. When water moves through a meandering channel, it will swing to the
outside of the curve, increasing its velocity. In contrast, water on the inside of the
curve will slow, allowing some of the suspended sediment to deposit. Because
these processes are continuous as long as the water flows, the shape of a
meandering river continues to change over time.
Figure 2. Aerial image of a meandering river, courtesy of the University of Oregon
(http:
pages.uoregon.edu/millerm/meander.html).
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PHYSICAL GEOGRAPHY LABORATORY
Straight Streams
The second type of river is straight. A straight river is characterized by a single,
uncurved channel. Straight rivers do not deposit much material, and typically the
su
ounding bedrock is more resistant to erosion, preventing sideways migration
of the river. Naturally occu
ing straight rivers are uncommon. One location that
has a mostly straight river channel is the Gunnison River as it flows through Black
Canyon of the Gunnison National Park, Colorado (Fig. 4). Notice how the river
channel does not have many major bends and there are tall rock cliffs
su
ounding the river. The bedrock in this area is more resistant to erosion
therefore not allowing the river to erode sideways.
Figure 3. Cross section of point bar (right side of b) and cut bank (left side of b).
Along the point bar, water decreases in velocity and deposits material. Along the
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PHYSICAL GEOGRAPHY LABORATORY
cut bank, water increases in velocity and will weather and erode the bank’s
material. The newly eroded material is ca
ied away in the river.
Figure 4. Example of a straight river in Gunnison National Park. The rocks forming
the sides of the canyon are extremely resistant to erosion, which does not allow
the river to bend. Image courtesy of the National Park Service
(https:
www.nps.gov
lca/learn/photosmultimedia/upload
lca_innercanyon01a.jpg).
Braided Streams
The final type of river that we will discuss is a
aided river. A
aided river forms
when the slope is gentle and there is a large amount of sediment in a river
(typically from steeper slopes and higher velocities upstream). The gentle slope
esults in slow water velocities, causing sediment to deposit. As the sediment
continues to settle out of the water, it builds into bars and the water is forced
around them into multiple channels. Figure 5 shows the
aided stream of the
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PHYSICAL GEOGRAPHY LABORATORY
Grewingk Glacier River in Kachemak Bay, Alaska. This water results from glacial
melt and it ca
ies large amounts of glacial sediment out of mountains towards
the sea. As the water flows out of the mountainous te
ain, the slope decreases
and, as a result, the water velocity slows. When water can no longer ca
y so
much sediment, the particles deposit.
Figure 5. Example of a
aided river system. Note how there are many small
channels of water. You can see the old channels that were diverted due to
sediment buildup. Braided river systems differ from meandering river channels in
that
aided systems have many river channels. Image courtesy of the National
Oceanic and Atmospheric Administration (https:
toolkit.climate.gov/image/1231).
Humans impact river systems in a variety of ways. We have changed how rivers
flow by building dams, levees, and floodgates, and by extracting the water. For
example, in southern New Mexico, people have straightened the path of the
meandering Rio Grande River so that they can “control” the river. These changes
allowed permanent housing settlements and farmland along the river channel.
Humans have also built large and small dams to collect water in reservoirs, such
as the Hoover Dam along the Colorado River or the Lake Thunde
ird Dam here in
Norman.
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PHYSICAL GEOGRAPHY LABORATORY
Part II. Channel Drainage Patterns
Over time, a stream system achieves a particular drainage pattern to its network
of stream channels and tributaries as determined by local geologic factors.
Drainage patterns or nets are classified on the basis of their form and texture.
Their shape or pattern develops in response to the local topography and
subsurface geology. Drainage networks develop where surface runoff is enhanced
and earth materials provide the least resistance to erosion. The texture is
governed by soil infiltration, and