Identify the dominant land uses surrounding the river.
PROCESSES AND LANDSCAPES
Note: Please refer to the GETTING STARTEDmodule to learn how to maneuver through, and how to answer the lab questions, in the Google Earth () component.
You should know and understand the following terms:
LAB LEARNING OBJECTIVES
After successfully completing this module, you should be able to do the following tasks:
· Describe the concepts of sub-basins and watersheds
· Identify different human water uses of a river
· Construct a stream order for a river system
· Compute drainage density of a given basin
· Identify drainage patterns of river networks
· Explain how braided rivers and meandering rivers are formed
· Identify the physical features common to a meandering river system
· Describe the physical conditions necessary to form alluvial fans
This module examines fluvial processes and landscapes. Topics include watersheds, drainage patterns and densities, stream order, meandering and braided streams, and alluvial fans. While these topics may appear to be disparate, you will learn how they are inherently related. The modules start with four opening topics, or vignettes, which are found in the accompanying Google Earth file. These vignettes introduce basic concepts of fluvial processes and landscapes. Some of the vignettes have animations, videos, or short articles that will provide another perspective or visual explanation for the topic at hand. After reading the vignette and associated links, answer the following questions. Please note that some links might take a while to download based on your Internet speed.
Expandthe INTRODUCTION folder and then select Topic 1: Introduction
Read Topic 1: Introduction
Question 1: Which of the following is a reason for the location selected for the first English settlement in the New World, Jamestown, VA?
A. Prime agricultural land
B. On the advice from the Native Americans
C. Deep water port
D. The land was already cleared
Read Topic 2: Rivers of Life
Question 2: If our ability to predict floods has improved significantly, why does economic loss continue to rise? (Check all that apply).
A. Increased urbanization
B. Increased population
C. Increased development along coasts
D. Increased real estate values
Read Topic 3: Rivers of Waste
Question 3: What are potential outcomes or conditions resulting from too much nitrogen running off from agricultural fields? (Check all that apply).
A. Eutrophication of water bodies
B. Decrease in crop production
C. Contamination of groundwater
D. Health issues in infants
Read Topic 4: Erosion
Question 4: List three ways in which humans contribute to stream bank erosion.
A. Vegetation removal
B. Increase in impervious surfaces
C. Wave from boats
D. Wind action on exposed banks
Read Topic 5: Transportation and Deposition
Question 5: What impacts do dams have on the transportation of sediment? Check all that apply.
A. Decrease in sediment transportation upstream from dam
B. Increase in sediment transportation downstream from dam
C. Decrease in sediment transportation downstream from dam
D. Increase in sediment transportation upstream from dam
Collapse and uncheckthe INTRODUCTION folder
For the remaining portions of this module, you will identify and explain the geographic distribution, patterns, and processes associated with fluvial environments. In doing so, you will recognize and appreciate the impact of rivers.
Expand the GLOBAL PERSPECTIVE folder and then expand the World Rivers folder. Double‑click and select any continent or world region. To display river information (name and approximate length) click any river in the Google Earth 3-D pane.
Collapse the World Rivers folder.
Major Cities on Rivers
Expand Major Cities on Rivers.
For each question below, type the latitude and longitude coordinates into the Search field and then press Enter. When you arrive at your destination, find the information that you will use to fill in the blanks below:
Question 6: 33 18 59 N, 44 23 33 E
Question 7: 30 03 29 N, 31 14 05 E
Question 8: 48 51 26 N, 2 21 04 E
D. Buenos Aires
A. Rio de la Plata
Question 9:Montreal, Canada.
Latitude: A. 45° 30’S B. 73° 33’N C. 45° 30’N D. 73° 33’S
Longitude: A. 45° 30’E B. 73° 33’N C. 45° 30’S D. 73° 33’W
B. St. Lawrence
Collapse anduncheck the GLOBAL PERSPECTIVE folder
WATERSHEDS AND DRAINAGE DENSITY
Expand the WATERSHEDS AND DRAINAGE DENSITY folder.
A drainage basin is an area of land in which a stream receives water, predominately by surface runoff, through flow, and groundwater flow. Drainage basins are topographically divided from each other by the highest points of elevation, so that all water from the ridges and hills flow into a given drainage basin and thereby into a given stream. This topographic delineation is commonly referred to as a watershed (the drainage divide between two drainage areas), although many in the United States use the term watershed interchangeably with drainage basin or catchment.
A large drainage basin can contain several smaller drainage basins or sub-basins. The nested nature of these sub-basins is determined by topography as well as where the water flows out of the drainage area, known as the outflow point.
In Figure 1, dash-lines A, B, and C demarcate the watersheds of the tributary streams, while dash-line D delineates the watershed of a larger drainage basin for the larger streams, which includes the smaller tributaries and their sub-basins.
Figure 1. Watershed map (Source: Maidstone Lake USGS 7.5 minute map).
Understanding watersheds are important because stream flow and water quality are influenced by the nature of and changes in the drainage basin. We can determine what is happening in our river basins by examining the water flow and water quality from a river’s outflow point. Changes to water flow or water quality in rivers could be due to either natural events (such as lightning induced forest fires increasing soil erosion) or human modifications (such as agricultural practices increasing pollution).
Double-click and select Columbia River Watershed.
The Columbia River watershed encompasses 258,000 square miles (approximately the size of France), with 220,000 square miles in the U.S. and 38,000 square miles in Canada. The length of the river is approximately 1243 miles, making it the 15th longest river in the United States.
Uncheck Columbia River Watershed.
Check the Columbia River Sub-basin US only folder. Click on each sub-basin in the Google Earth map pane to identify its name.
Question 10: How many Columbia River sub-basins in the United States are displayed on the map?
Uncheck Columbia River Sub-basin US only.
Expand the Columbia River Watershed – Fly Over folder.
The Google Earth flying simulation of the Columbia River shows how the basin is a multi-use watershed. Do the following steps to reduce confusion for the duration of the simulation:
Question 11: What water uses did you see as you traveled upstream on the Columbia River? (Check all that apply).
B. Flood control
C. Power generation
Uncheck Columbia River Watershed – Fly Over.
Expand the Stream Orderfolder.
Figure 2. Stream order (16.9 Arbogast 2nd. Ed.).
Stream order is a measure of the size of a stream based on a hierarchy of tributaries. Using the Strahler stream order method, the smallest tributaries are assigned the value of 1. When two streams with different order numbers join, the resulting stream is assigned the value of the higher order numbered stream.
In Figure 2, two streams with an order number of 1 join to form a stream with an order number of 2. However, when one stream with an order number of 1 joins a stream with an order number of 2, the stream remains a 2. Large river systems typically have a higher stream order. The Mississippi River for example has a stream order of 10.
The Strahler stream order number for a given stream is dependent on the scale as which one views a stream network. A stream with an order number of 3 on a 1:24,000 map, for example, might have an order number of 1 on a 1:1,000,000 scale map, as fewer rivers are displayed on a smaller scale map.
Double-click and select the Willamette River folder.
In this particular map, the Willamette River has a Strahler stream order of 5. Though not all streams are labeled with their order, you should be able to determine how the stream ordering system works. You might have to zoom in to see the labels clearly.
Double-click and select the Snake River folder.
For Questions 12 to 15, identify the stream order number for rivers A, B, C, and D:
Question 12: River A:
Question 13: River B:
Question 14: River C:
Question 15: River D:
Uncheck the Stream Order folder.
Double-click and select the Stream Density folder.
Figure 3. Drainage basins (16.8 Arbogast 2nd. Ed.).
Notice the two sub-basins that are highlighted. The smaller one is the Willamette River watershed and the larger one is the Snake River watershed. The drainage density of a basin measures how well a watershed is drained and depends largely on the underlying bedrock and topography of the basin. Basins with high relief and exposed bedrock tend to have a higher drainage density.
Use the following formula to calculate the stream density of each sub-basin (show your work):
In other words, the [drainage density] equals the [total length of all streams] divided by the [area of the drainage basin]
Double-click and select Snake All Streams.
Double-click and select Willamette All Streams.
Willamette River watershed:
The area of the Willamette River sub-basin is 11,500 square miles.
The total length of all streams in the Willamette River sub-basin is 12,800 miles.
Question 16: What is the stream density of the Willamette River sub-basin?
A. 12800 / 11500 = 1.11
B. 11500 / 12800 = 0.90
C. 12800 / 11500 = 1.43
D. 11500 / 12800 = 0.95
Snake River watershed:
The area of the Snake River sub-basin is 108,000 square miles.
The total length of all streams in the Snake River sub-basin is 138,000 miles.
Question 17: What is the stream density of the Snake River sub-basin?
A. 108000 / 138000 = 0.78
B. 138000 / 108000 = 1.28
C. 108000 / 138000 = 0.83
D. 138000 / 108000 = 1.48
Collapse and uncheck WATERSHEDS AND DRAINAGE DENSITY folder.
Expand the DRAINAGE PATTERNS folder.
Figure 4. Drainage patterns (16.7 Arbogast 2nd Ed.).
The drainage patterns of a stream system (a network of streams and tributaries) depend largely on the topography on the land as well as the structure of the underlying bedrock. Areas subject to faulting often produce rectangular drainage patterns, while areas with folded topography (mountains) often have trellis drainage patterns. Volcanoes typically form radial drainage patterns. Dendritic drainage patterns are common in areas with non-porous, impermeable bedrock.
Double-click and select Drainage pattern 1.
Question 18: Identify Drainage pattern 1:
Now that you have identified Drainage pattern 1, double-click and select drainage patterns 2 to 5 to identify them.
Question 19: Identify Drainage pattern 2:
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