Field Trip Number One. By: Pat Dryer. Geography 360

Transcription

1 Field Trip Number One By: Pat Dryer Geography 360

2 Table of Contents Introduction. Page 1 Stop One... Page 2 Stop Two... Page 4 Stop Three... Page 5 Stop Four... Page 7 Bibliography Page 8 Campus Map Source:

3 1 Summary The purpose of the field trip was to familiarize oneself with many geomorphic features that are prevalent on campus or near the UWEC campus. The first trip was to introduce the concept of using field notebooks. There are many features that are located very close to the campus including cut banks, point bars, and many other features. We also looked at how the University compensated for some potentially dangers situations because of the location that the University sits on. The University recently invested a great deal of money into the riverbank reconstruction pictured below in Figure 1. Figure 1- The newly reconstructed cut bank on the University of Wisconsin- Eau Claire campus was completed in the summer of The goal of this project was to stop the erosion that was occurring to the south bank of the Chippewa River. Notice the sediment deposit in the bottom right of the photo (point bar).

4 2 Stop One Stop one was located on the north side of the Chippewa River near the Haas Fine Arts Center. Conditions at stop one were partly cloudy skies, with an approximate temperature of 85 degrees F, and a relative humidity of 75%. On the point bar, I primarily faced the cut bank that has been recently reconstructed near the Putnam Residence Hall on Garfield Avenue. A cut bank is a geomorphic feature that is typically associated with steep slopes and deep river depths directly in front of the cut bank. Cut banks are formed when rivers take a bend and the sweeping current causes erosion to the bank, this is pictured in Figure 1. Stop one is also considered a point bar (Figure 1). This also is a place where sediments have been deposited by the river. This particular point bar is a migrating point bar which literally moves over time and can be proven with aerial photographs from years past. The point bar has migrated down stream over the past years and is still slowly migrating further downstream. Furthermore, the point bar is protected by a feature called rock armor. Rock armor is a deposit of larger rock/stone that is protecting the sand from eroding. This rock keeps the point bar from being easily eroded through flooding and strong river currents. It is clear which way the stream flow is by looking at the position of the rocks in the rock armor. The rocks are positioned by currents so that the water easily flows over the top, otherwise the river would pick up the rock and move it down stream (Figure 2). Figure 2- The river flow can be noted by the shape of the rocks pictured. The rocks are shaped from collisions of rocks and other sediments that bounce across the bottom carried in the river load.

5 3 I noticed that the deposited rocks are fairly large in size, and approximately five inches in diameter. The rocks downstream are much smaller and more gravel like. This point bar is located on the flood plain of the Chippewa River. This can be observed in Figure 3 by the very minimal vegetation on the point bar and also by the sand deposits 10 yards inland. This shows that the river deposited the material there at some point in time. It is obvious that the Chippewa River floods time to time from the high water marks on the bridge pillars. This can also bee seen in Figure 1 by the brown discoloration of the bridge pillars. It is also important to know that the Chippewa River is controlled by a dam that minimizes flooding throughout the year. When flooding does occur, it is visible because the flood waters that are filled with leaves and sediment washed away by the fast current. This leaves a brownish stain on the white concrete bridge pillars. As I walked upstream, I noticed that the sediment that was deposited was much smaller than the depositie at stop one. The deposits are more gravel like and the largest diameter or rocks are approximately two inches in diameter. I also noted that there was algae growth in the water just offshore of the point bar. This indicates that there is little movement in the water, otherwise the algae would not be able to grow. This shows that the current is much slower near the point bar. Figure 3- There is minimal vegetation on the point bar, it isn t until further inland that trees and small shrubs are more abundant.

6 4 Stop Two Stop two is located on the south side of the McIntyre Library, between the library and Little Niagara Creek. The conditions at stop two were pleasant with overcast skies and temperatures near 70 degrees F. The purpose of stop two is to observe the location of the Library with respect to Little Niagara Creek. The McIntyre Library was built on the flood plane of the creek. This means that if the creek was to flood, the library would become partially submerged. To compensate for this potential problem the library was built on a series of pillars so that flood waters will not harm the building. These pillars can be observed in Figure 4. Vegetation is prominent on the banks of the creek as well as some vegetation growing in the water as well. The water in the creek is fairly clear and fast moving in certain areas. As I progressed downstream I noticed that the creek began to widen. Large culverts divert water into the creek from the marshes and storm drains located on the south side of Phillips Parking Lot. The grade of the land surrounding the creek slowly descends towards the creek from bank of the Chippewa River. There is a noticeable cut bank downstream from the culverts that are slowly creating a point bar just downstream from the location. As I progress downstream further, I encounter the flood control dam that was created to stop flood waters from the Chippewa River backing up into the creek. Figure 4- The McIntyre Library was built on a series of pillars to protect itself from a flood of the Little Niagara Creek.

7 5 At this location there are very large pumps that will pump the water over the damn and into the Chippewa River if flood stage were to be reached. The flood control system is controlled by a large gate that swings down once the water in the Chippewa River reaches flood stage. When the gate is closed water is restricted from backing up into the creek. The gate also prevents water in the creek from flowing into the Chippewa River. The pumps are then activated to pump the water from the creek over the wall and into the Chippewa River to protect the creek from backing up and flooding valuable land located upstream. Once I crossed Garfield Avenue the sand in the river began to decrease. Within a few yards downstream there was little to no sand at all in the river bed. The river bed was primarily a entrenched meander. An entrenched meander is created when a river slowly erodes through the bedrock over years and creates a canal for the water to flow. Because of the erosion there are large areas of bedrock outcropping. This is where the river banks are steep and the bedrock protrudes from the ground. Figure 4 is a great example of a entrenched meander and bedrock outcroppings. Downstream the river flows primarily over bedrock. Figure 4- A photograph of an entrenched meander that Little Niagara Creek has formed near the Chippewa River.

8 6 Stop Three Stop three is located at the point where the Little Niagara Creek empties into the Chippewa River. This point is also known as a nick point. A nick point is where the water is forced over a particular object, in this case bedrock, and creates a waterfall. The nick point is slowly eroding away due to the constant steady flow of the stream. Figure 5 illustrates the various canals and other features that have been worn into the bedrock from years of erosion. There is an outcropping of bedrock on the Chippewa River near this area. There is a gravel upstream as well as downstream from location, and a gravel bar is located directly in front of the nick point in the Chippewa River. This gravel is a result of the erosion of the point bar and the river depositing the material downstream. There is evidence of back eddies that formed here near the nick point. A back eddy is a cove where water flows into and circulates. This circulating water creates potholes in the bedrock which is visible in Figure 6. Water can reach these areas when flooding occurs. Figure 5- This is a picture of the nick point of the Little Niagara River, water has slowly eroded the bedrock over time.

9 7 Figure 6- This pothole was created when flood waters were high enough to flood the nick point and create a back eddy. The back eddy created a swirling the water current and eroded the bedrock in a unique way. Stop Four Stop four was located on a portion of the newly reconstructed riverbank on Garfield Avenue. The goal of this project was to reconstruct the cut bank with the placement of large rock and cement pillars embedded into the riverbank. The purpose of this reconstruction was to stop erosion and protect the infrastructure directly behind the river bank. The infrastructure includes many utility lines, water mains, as well as residence halls located near the riverbank. Many university buildings are built on the natural levy that has resulted from flooding on the Chippewa River. This levy protects many of the buildings, but in recent years there has been fear of erosion to this natural levy. From this location the point bar is directly across the Chippewa River which was of interest in stop one. The newly re-engineered riverbank project is pictured in Figure 1.

10 8 Bibliography University Publications, University of Wisconsin- Eau Claire Campus map, 1sheet.