Instruction
A stream's gradient is the slope of a stream, or its change in elevation over a given horizontal distance. More simply, the gradient is the distance the stream falls vertically from one point on the landscape to another. To learn more about the gradient and how to calculate it, watch this Youtube video.
https://www.youtube.com/watch?v=ykeCKm9JqSA
Streams are like lines that flow across the landscape, and a stream's gradient is the slope of the flowing stream. To calculate the stream gradient, you simply identify the change in elevation of a stream and divide this change in elevation by the measured horizontal distance over which the stream has flowed.
Schematic Stream Examples
Below are two schematic drawings of streams flowing across two contour lines (changes in elevation) from Point A to Point B. Calculate the gradients of each of these streams and add the answer to the attached answer worksheet.
Example A
The contour lines are the vertical lines and the stream is the line running between A and B. The contour lines tell you the change in elevation. Every contour line crossed is one contour interval of elevation. In this example, the contour interval is 25 m and two contour lines are crossed.
The horizontal distance is based on the map scale. The map scale in this example is 1:15000, which means that every 1 cm on the map is 15,000 cm in real life. In this example, the length of the line running between A and B on the map is 2 cm.
Answer the following questions on the attached answer worksheet.
a) What is the change in elevation in meters between Points A and B?
b) What is the horizontal distance between Points A and B in kilometers?
c) The stream gradient is the change in elevation divided by the horizontal distance. What is the stream gradient in m/km?
Example B
In this example the contour interval is 10 m and the map scale is 1:5000. The length of the line running from Point A to Point B is 2 cm.
Answer the following questions on the attached answer worksheet.
a) What is the change in elevation in meters between Points A and B?
b) What is the horizontal distance between Points A and B in kilometers?
c) The stream gradient is the change in elevation divided by the horizontal distance. What is the stream gradient in m/km?
Philipp, Mississippi Quadrangle Map
The image below is a section of a contour (elevation) map entitled the Philipp, Mississippi Quadrangle map. The river depicted is a section of the Tallahatchie River just north of the town of Philipp. The distance between the "mile 210" and "mile 215" points following the wide meandering oxbow is 8.25 miles. The distance between these two points following the Pecan Point Cutoff, which is an artificial cutoff that has shortened the length of the stream, is 5.05 miles. Using this information and what you know about stream gradients, answer the following questions on the attached answer worksheet.
a) How many miles is saved by the cutoff?
b) If the elevation is 119 ft at mile 215 and 116 ft at mile 210, the gradient between these two points using the oxbow meander is how many ft/mi?
c) What is the gradient using the Pecan Point Cutoff?
Assignment #2
Water dowsing (also known as water witching) is a pseudo-scientific practice (meaning it is a practice that incorrectly claims to be scientific without adhering to the rigorous processes and procedures of the scientific method) of using some kind of simple instrument (often some kind of L-shaped or Y-shaped stick or rod) to locate underground water resources. This practice is a kind of divining, where the practitioner invokes an unseen force, through the medium of the dowsing rod, to locate the water. Water dowsing is often employed prior to digging a well or cistern.
Unseen forces do exist in the natural world and can be measured and used by scientists to locate materials. For instance, Earth's magnetic field is an unseen force generated by movement of heat in convection cells within the planet's iron and nickel core. Scientists use instruments called magnetometers to measure aspects of Earth's magnetic field to, for instance, locate buried ore deposits. However, scientific studies of dowsing have demonstrated that, while some dowsers are able to locate water, the success rate of dowsing is no better than chance. That is, the dowser's likelihood of locating water is the same whether the person is dowsing or just pointing at a random spot in the yard and saying there's water there.
In this exercise you are going to learn more about dowsing as a pseudo-scientific practice and use your knowledge of Earth science to critically evaluate the practice. To begin, let's learn about dowsing from someone who practices the craft and believes in its efficacy. Watch the following Youtube video:
Water Dowsing
https://www.youtube.com/watch?v=VrrN6UYZj38
Now, let's learn what Earth scientists say about water dowsing and the science of water (known as hydrogeology). Read this pamphlet on dowsing published by the United States Geological Survey (USGS):
USGS Pamphlet on Dowsing
This is a short essay assignment. All short essays submitted for this course should be written in complete sentences and full paragraphs, each with a coherent beginning, middle, and end. A rule of thumb for short essay lengths is 2-3 full sentences per question.
For this assignment you are to write a 3 to 4 paragraph short essay comparing and contrasting the methods of science with the methods of water dowsers. How do these practices differ? How do the beliefs and practices of water dowsers contrast with the scientific process? What makes water dowsing pseudo-science rather than actual science, and what evidence do we have that water dowsing is an unreliable and non-scientific method of understanding Earth's natural features and processes?
Assignment #3
Wetlands are a vital component of the hydrosphere. They are Earth's natural water filtering mechanisms and they provide diverse habitats for numerous species of plants and animals. Read more about Indiana's wetland resources in the following article by Eric Myers, originally published in the book The Natural Heritage of Indiana.
Lifeblood of the Land: Water
For this reflective essay, I would like you to write 4 to 5 paragraphs reflecting on your use of wetlands. Perhaps you grew up near wetlands or regularly go fishing or hunting in wetland environments. If so, write about these experiences and the positive impact wetlands have had on your life. If you do not regularly use wetlands, reflect on the value of wetlands in more general terms. How do you benefit indirectly from our wetlands and how would their loss negatively impact your life?
Each paragraph should average 4 to 5 full sentences. I'm looking for a complete, well thought out essay here. Be thorough and descriptive in your essay and be sure to draw on the materials covered in the course directly. For full points, you should not simply write an opinion piece - you must back up your opinions with facts derived from the video and your readings and assignments.
Assignment #4
Google Earth - Drainage Patterns
Google Earth is an interactive 3D satellite image and virtual mapping software program that allows you to navigate to and view various locations on the planet from a bird's-eye view. The program provides satellite images of the Earth's surface and is interfaced with Google maps. To navigate to different locations, you simply double-click on the location you wish to zoom in on, or you can type in location names or coordinates in the search menu at the top-right of the screen. In some areas you can enter 'street view' and navigate streets as though you were traveling in a vehicle along that road.
In this assignment you will use Google Earth to navigate to five different stream locations. Answer each of the questions about that location using the attached worksheet. Save the worksheet and submit it as an attachment to this assignment for grading.
Download Google Earth
If you do not have Google Earth installed on your computer, you can download it for free from the following website:
Google Earth
Once Google Earth is installed, open the attached worksheet and answer the questions.
Drainage Patterns
You learned about the various kinds of stream drainage patterns in the Drainage Networks & Patterns video in Connect. This assignment applies what you learned to the identification of drainage patterns in real-world contexts using Google Earth.
1. Use the Google Earth search menu to navigate to:
S 3 11.327 W 064 37.412
To do this, just type the above latitude and longitude coordinates into the search menu or copy and paste the text. At the bottom right of the screen you should see that the eye alt (the altitude at which you are viewing the landscape) is about 3425 ft. Use the zoom slider at the top right of the map to zoom out to an eye alt of approximately 1700 miles. Identify the dominate stream drainage pattern at this location and write this pattern on the answer worksheet
2. Use the Google Earth search menu to navigate to:
N 39 25.343 W 078 32.391
Adjust the eye alt to approximately 20 miles. Identity the dominant stream drainage pattern at this location and write this pattern on the answer worksheet.
3. Use the Google Earth search menu to navigate to:
N 35 08.046 W 119 40.400
Adjust the eye alt to approximately 8000 ft. Identify the dominant stream drainage pattern at this location and write this pattern on the answer worksheet.
4. Use the Google Earth search menu to navigate to:
N 46 52.071 W 121 43.590
Adjust the eye alt to approximately 35 miles. Identify the dominant stream drainage pattern at this location and write this pattern on the answer worksheet.
Stream Type
In the Connect video Stream Components & Processes you learned about a particular type of stream and its floodplain features.