Streams and Rivers Lab:
Introduction to Fluvial Geomorphology

Geomorphology is the study of the Earth's landscapes and landforms, the processes by which the landforms originated, their age, and the nature of the materials underlying them. Fluvial geomorphology is the study of landforms and processes associated with rivers.

The Fluvial System Model

A model is a simplified idealized representation of reality. The basic fluvial system can be represented as a model in order to help us understand its structure and processes. The basic fluvial system is often considered to be a drainage basin. Drainage basins differ in size and complexity, and are often subject to scale considerations. Often, a small watershed is part of a tributary to a much larger drainage basin. The following diagram of a fluvial system is an idealized representation to help you conceptualize its structure. The diagram is presented as three nested basins of small, medium, and large scale.

Zone 1: Drainage Basin or Watershed

• principal area from which runoff flows
• principal area from which dissolved solids and sediments are derived

Zone 2: Area of Transfer

• inflow of water roughly equals outflow
• assuming stability, influxes of dissolved solids roughly equals fluxes out

Zone 3: Area of Deposition

• discharge of water into larger streams or bodies
• influxes of dissolved solids roughly equals fluxes out
• alluvial-fan and alluvial-plain environments
• estuarine and deltaic environments
• costal environments
  

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Exercise I: Stream Drainage Patterns

PRE-LAB ACTIVITY:

Below are descriptions and illustrations of a number of classic drainage patterns. In lab you will be asked to identify some of these features (and others) on topographic maps, aerial photographs and remotely sensed imagery. You should review your knowledge about drainage systems by studying these illustrations as well as those shown in your textbook. You will be asked to answer some questions in writing on a lab sheet that will be provided. Try also to answer the questions included here - how many of these places can you identify?

Note: The following exercises are done in a "sit-down" lab at Loma Linda University, Geoinformatics Lab.

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Background:

NOTE: Review materials on Map Interpretation from Topic #5 and Lab #3

A topographic map represents the landscape as seen from above. Often this perspective does not give us the information needed to adequately visualize the land surface. We are accustomed to viewing landscapes from a horizontal perspective. In studying various landforms it may be desirable to construct a profile, or a cross-sectional diagram, through important areas in order to get a better perspective from a more natural viewpoint.

Methodology:

Cut-line. A topographic profile begins with the selection of starting and ending points. Once the points are selected they are joined with a straight line called the cut-line.


Vertical scale. The vertical scale on a topographic map is the same as the horizontal scale because there is no direct representation of vertical distances on a map. With topographic profiles vertical distances are directly visible. And, in topographic profiles, vertical scale may not be the same as horizontal scale. In a topographic profile if the horizontal scale is smaller than the vertical scale of the cross section there is said to be vertical exaggeration. Vertical exaggeration is used to make the topographic profile more visually appealing or to obtain elevation differences that are more easily measured. In general, more exaggeration is needed in areas of low relief and less in areas of high relief. So, what is the appropriate vertical exaggeration? In many instances a 5x exaggeration of vertical distance is appropriate, where the horizontal distance would remain the same. This means that on a 1:24,000 topographic map, where 0.5 inches equal 1000 feet, on the vertical scale on the profile 1000 feet would equal 2.5 inches.

Step-by-step Instructions:

• Lay a strip of paper along the cut-line.
• Mark on the paper the exact place where each contour, stream, and hilltop crosses the cut-line.
• Label each mark with its elevation recorded from the contour line. If the contours are closely spaced you may only need to label the index contours.
• Determine the maximum and minimum elevations from the data you collected. For the maximum round up to the nearest index contour, for the minimum round down to the nearest index contour.
• Determine the scale of the topographic map from which you collected the data.
• Determine the contour interval. Note whether it is in feet or meters.
• Determine what vertical exaggeration you want (1x, 2x, 3x, 4x, 5x, ...). If you choose larger than 1x be sure there is enough space on your graph paper.
• Prepare a vertical scale on the graph paper by labeling horizontal lines to correspond to the elevation of each index contour line. (Remember with a 5x exaggeration if you are working with a 1:24,000 topographic map, where 0.5 inches equal 1000 feet, on the profile 1000 feet would equal 2.5 inches.)
• Place the paper with the labeled marks at the bottom of the profile paper and project each contour onto the horizontal line of the same elevation.
• Connect all the points with a smooth line.
• Label the x-axis, the y-axis, and all other pertinent features.

Exercise Questions to Answer: Topographic Profile

1. What is the scale of the Leefe, Utah-Wyoming Quadrangle?
2. What is the minimum elevation along the cut-line (rounded down to the nearest index contour)?
3. What is the maximum elevation along the cut-line (rounded up to the nearest index contour)?
4. What is the name of the river that the cut-line crosses?
5. What is the direction of its flow?
6. Construct a topographic profile for the cut-line identified on the Leefe, Utah-Wyoming Quadrangle. Use a 8x vertical distance exaggeration.
7. Label the major features on your topographic profile.
8. Identify the following features on the topographic map (A-F):

_____meander

_____oxbow lake

_____ephemeral stream

_____back swamp

_____perennial stream

_____natural levee

_____yazoo tributary

_____meander scar

9. Does this river show signs of youth, maturity, or old age?
10. Studies of meandering streams show that a relationship exists between the width of a channel and the diameter of the meander loops, the larger the channel width, the larger the loop. Why should this be true?

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Exercise 3: Landscape Evaluation

Stereo Pair 1

1. Observe the stereo pair through the stereoscope.
2. Using the acetate film as an overlay draw a line corresponding to the major fault.
3. Locate and label one example each of the following features: cinder cone, series of faceted spurs, basalt lava flow

Stereo Pair 2

1. Observe the stereo pair through the stereoscope.
2. Describe what you see through the stereoscope.

1. Where is the likeliest position of the Wasatch Fault?

1. Knowing that the stereo pair is located along the Wasatch Fault, name the lake and major mountain peak.

Lake:__________________________________Peak:______________________

Stereo Pair 3

1. Observe the stereo pair through the stereoscope.
2. The area has been subject to some Earth system process. What was the process?
3. Using the accompanying scale determine the diameter of the largest crater (find the largest diameter).
4. What are the features called that dominate the photo? How many are in the left photo?

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Exercise 4: Spatial / Locational Reference Systems

NOTE: Review materials on Map Interpretation from Topic #5 and Lab #3

On the typical USGS 7.5-minute topographic map (1:24,000) there are up to four locational reference systems. These are (1) longitude-latitude; (2) Universal Transverse Mercator, or UTM; (3) township and range, or USPLS (US Public Land Survey); and (4) state plane coordinate system. The border of each map contains the information needed to locate any object via one of these systems. The most common system is longitude-latitude, a global coordinate system.

Determining the longitude and latitude of an object on a 7.5-minute quadrangle is a simple and straightforward task. The figure below illustrates the graticular network visible on a quad. Running north-south are lines of longitude, and running east-west are lines of latitude. From the line of latitude on the top of the map (the top map border) to the line of latitude on the bottom of the map (the bottom map border) is a difference of 7'30", or 7.5-minutes, of latitude. Similarly, from the left border to the right border is a difference of 7'30", or 7.5-minutes, of longitude. Intermediate to these index lines, the 7.5-minute quadrangle is subdivided into 3 increments each 2.5-minutes in longitude and latitude.

At each of the corners of the map the coordinates are identified. For example, the coordinates for the south-west corner (lower left) are 40o37'30"N latitude (north of the equator) 111o52'30" W longitude (west of the prime meridian). Each of the 2.5-minute tics are abbreviated (40' is actually 40o40'00"). Because the longitude-latitude system is not a grid based system, at the latitude of the map we are working with the distance between 2.5-minutes of longitude will not be the same as that of 2.5-minutes of latitude. This is due to convergence of the lines of latitude at the north and south poles.

To determine the longitude-latitude of any feature on a 7.5-minute map there are three simple steps:

1. Using a straight edge ruler connect the intermediate tics on your map. The intermediate tics are represented by small black lines protruding into the map area from the border. At the intersection of each of the tics there is a cross-hair (+) where they intersect. Accuracy is essential when connecting the tics. Be sure you are using the correct tic, for there are blue tics for UTM, red tics for USPLS, and black tics protruding out into the map border for the State Plane coordinate system.

2. Determine the distance between known lines of latitude and known lines of longitude. Figure 2 is an illustration of the lower left quadrant in Figure 1.

3. The MATH SECTION.

Tips: For ease of math use a metric or engineers scale (ruler).

Always measure from the line of lowest longitude or latitude to the line of highest longitude or latitude (from bottom to the top for latitude and from the right to the left for longitude).

Exercise: Longitude-Latitude

Determine the longitude-latitude for the following points on the Sugar House Quadrangle.

a) Westminster College

____o___ '____ "__ longitude

____o___ '____ "__ latitude

b) Mount Olympus

____o___ '____ "__ longitude

____o___ '____ "__ latitude

Exercise: Stream Profile

Using the Sugar House Quadrangle construct a stream profile for Parley's Creek as it cuts across the valley. Use at least a 4x vertical distance exaggeration and identify an appropriate exaggeration/reduction to fit on the graph paper. Identify major cultural and physical features along the profile including the locations of any nickpoints, tributaries, roads, etc... Remember to label the x and y axes.

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