Matanuska River Channel Change:Final Project

Introduction

The goal of this geospatial project was to determine how much the Matanuska River has changed over time and how close to the Glenn Highway the river has gotten over the years. 74 miles in length, the Matanuska River is a braided stream located within the Mat-Su Valley of South Central Alaska. Beginning at the Cook Inlet, the river follows the scenic drive of the Glenn Highway, and ends at the Matanuska Glacier. The Glenn Highway is one of the only means of transportation for residents and tourists to drive from Tok, to Palmer. The Matanuska River has a history of erosion, and homes washing away.  Over the years, the river has become extremely close to the highway. The importance of the project is to show how close bthe Matanuska River has gotten to the highway through channel change. The motivation for this project was figure 1.

Figure 1: erosion, just outside of Sutton-Alpine

The study area chosen for was Palmer, Alaska

Figure 2: Study area, the Black dot is Palmer, the Red dot is the location of Figure 1

Data and Methods:
An important part of this lab was to observe literature that used similar methods.  A major source for this project was the USGS report in 2011: Geomorphology and Bank Erosion of the Matanuska River, South-central Alaska by Janet H. Curran and Monica L. Mcteague. The report examined 65 miles of the Matanuska River to asses river bank erosion. Aerial images from 1949-2006 were obtained from this project, while the rest of the images were obtained from Google Earth Explorer. shape-files were obtained from the Alaska geospatial clearinghouse. 

Images from 1949-2006 were clipped as well as 2017. the images were placed in their own geodatabase. Shape-files for Alaska towns were obtained through the Alaska geospatial clearinghouse. A new feature class was created for the towns of Sutton and Palmer. A new feature class was also created for each image so that they could be digitized.

Figure 3: Georeferenced images

Each image obtained was georeferenced as observed in figure 3, except 2012 due to complications with arcgis crashing, or not loading. A table was made using Microsoft Excel to see how close the river has gotten to the Glenn Highway.

Results:
The river bed in the images was digitized as seen in figure 4.

Figure 4: Digitized river bed from 1949-present

 Using the measure tool, the river bed was measured in feet where the red arrow is in figure 5, to see how close its gotten to the Glenn Highway each year.

Figure 5: The red arrow is where the river was measured to the Glenn Highway

Figure 6 shows the results of the measure tool, and how close the river has gotten to the road each year.

Figure 6: table showing how close the river has gotten to the Glenn Highway over the years.

Conclusion
The Matanuska River has changed considerably over the course of history. In 1949 the river was 1,049 feet from the Glenn Highway, as compared to 2017 where it was 1,209 feet. There are a number of years missing in this analysis to really notice the difference. Images from 1950s, 1970s, 2012, are missing from this project due to time constraints.

Future Work
The original focus of this project was the area where figure 1 is located, but due to lack of data, the study area was moved to Palmer. Imagery of the location of figure 1 was mailed on a flash drive from the Matanuska-Susitna Borough and obtained several days ago. Using similar methods, comparing the two locations would make for a nice analysis and show how the river channel changes farther north.

Sources: 

"Alaska State Geo-Spatial Clearinghouse". 2017. Asgdc.State.Ak.Us. http://www.asgdc.state.ak.us/.

Curran, J.H., and McTeague, M.L., 2011, Geomorphology and bank erosion of the Matanuska River, southcentral Alaska: U.S. Geological Survey Scientific Investigations Report 2011–5214, 52 p.

Curran, Janet H., Michael G. Loso, and Haley B. Williams. 2017. "Glacial Conditioning of Stream Position and Flooding In the Braid Plain of the Exit Glacier Foreland, Alaska". Geomorphology 293: 272-288. doi:10.1016/j.geomorph.2017.06.004.

"Google Earth Engine Explorer". 2017. Explorer.Earthengine.Google.Com. https://explorer.earthengine.google.com/#workspace.

 Admin, June. 2017. "Matanuska-Susitna Borough - GIS Downloads". Matsugov.Us. https://www.matsugov.us/gis-downloads.

U.S. Army Corps of Engineers, 2003, Expedited reconnaissance study, section 905(b) (WRDA 1986) Analysis, Matanuska River Erosion, Matanuska-Susitna Borough, Alaska, 30 p.