Land Cover Changes on the Lower St. Croix Between 1984 and 2010

UNIVERSITY OF MINNESOTA

FR 3262 / 5262, Section 1 – Spring 2013

Josiah Emerson, Cynthia Ratzlaff, Majory Silisyene 5/10/2013

1. Introduction The Lower St. Croix National Scenic Riverway is the last 52 miles of the St. Croix River flowing from St. Croix Falls, Wisconsin and Taylors Falls, Minnesota (see figure 1 in Appendix 1) and ending in

Prescott, Wisconsin where it joins the Mississippi River. The Lower St. Croix Riverway comprises of

25,346 acres of land and water, and it is jointly managed by the National Park Service (NPS) and the

Department of Natural Resources (DNR) of the states of Minnesota and Wisconsin. 9,542 acres of land and water of the upper 27 miles of the river is under a federally administered zone, while 15,804 acres of land and water of lower 25 miles are under state administered zone, even though the management responsibilities between the NPS and the states overlap in some areas. While most of the land in this region is managed by the two states and the NPS, much of the land on the lower 25 miles of the river is under private ownership, and thus, is managed under scenic easements. The three types of classes of natural resources under the Wild and Scenic Rivers Act are wild, scenic, or recreational - the first 10 miles of the Lower St. Croix are designated scenic and the last 42 miles are designated recreational. All rivers designated by this act are managed as a valuable resource that should be protected.

1.1. Background information

In 1972 the Lower St. Croix River was added to the National Wild and Scenic River System

(NWSRS), and in 1975, the original boundary for the river was published (Cooperative

Management Plan, 2002). The river provides clean water, high quality natural ecosystems, striking geologic features, beautiful scenery, and abundant recreation opportunities. The watershed of the river is considered to be one of the most biologically diverse rivers in the Upper

Mississippi River basin. Its sloughs and backwaters, as well as the relatively intact vegetation along its banks, are home to a rich variety of native and endangered species and habitat. Despite

2 the fact that the river has been said to be in pristine condition, its adjacency to metropolitan areas make it more prone to degradation. Development pressure, however, is building as the twin cities metropolitan grows each year and expands outwards. With the advent of development becoming closer and closer to the river and with the river in the same watershed as a potentially large urban city, there is a very real threat to the Lower St. Croix River. 52 miles of which are located in the same watershed as the twin cities.

Since its inclusion in the NWSR, it has been claimed that the area has remained in pristine condition. We, however, argue that the private land owners have continued to convert their lands into other uses despite the implementation of the Wild & Scenic Rivers Act (WSRA) of 1969 – that is, some privately owned land may have been converted from forest to either developed or agricultural uses, and thus, land cover may have changed. As agricultural resources are rising in price per bushel of corn, it is expected that many people will take that chance to make money and grow as much as possible on the land they own with or without regards for their scenic easement agreements or the river on which they border. A portion of the land along the river is agricultural land that could potentially have runoff from poor farming techniques. Our argument comes as a result of the need for people to utilize their lands more profitably; therefore, not abiding to agreements made in the scenic easements.

1.1.1. Evidence supporting our hypothesis

Urban sprawl has increasingly affected the southern portion of this watershed, with metropolitan communities (e.g. Oakdale, Woodbury, and Mahtomedi) expanding east further into the watershed. Woodbury was the third fastest growing city in the metropolitan area, expanding by 12,875 residents between 2000 and2009 (MET Council, 2009). From 2000 to

3 2010, Washington County grew by 18%, among the highest growth rate for counties in

Minnesota (Census Bureau 2012). According to the Minnesota Pollution and Control Agency

(2012), “Urban growth results in more impervious surfaces (e.g. parking lots, driveways, roads, sidewalks, rooftops) which impede natural infiltration processes, and can lead to higher runoff rates, increased sedimentation and altered thermal regimes in urban waterways” (p. 15). Using remote sensing and geographic information system (GIS) techniques, we will be able to show that our claim is valid or not.

2. Project description and objectives

Lower St. Croix Riverway has been reported to have remained in pristine condition for many years, suggesting success of the implementation of the WSRA of 1969 and the amendments that followed. While there were no reasons for casting doubts over the pristineness of the Lower St.

Croix Riverway, we strongly believe that there may be land cover changes in the area, especially in privately owned lands, because scenic easements may not be considered profitable (in comparison to other investments such as the rising price of corn this year) by some land owners.

Therefore, we tested the hypothesis that land cover in privately owned lands has changed over the past twenty-six years of implementation of the WSRA of 1969. The results of the analysis aim at informing the public on whether the WSRA and scenic easements have had a significant impact on privately owned lands in conserving the wild and scenic areas or not. Therefore, our project involved the use of images acquired by LandSat 5 satellite for two different years (1984 and 2010) - we compared the land cover before and (2010) after this historic legislation. We then measured the changes in cover types and in private lands found within 500meters. The area we

4 analyzed includes only parts of Afton and Denmark Townships. This area included the scenic easement and the land immediately adjacent to that easement. Our two specific objectives were:

1. To analyze land cover in private lands within 500meters. from the St. Croix River.

2. Determine land cover changes within our study area by comparing land cover before and

after the implementation of the WSRA of 1969.

Using remote sensed digital images to determine land cover changes was critical because it is cheaper compared to other means such as physical measurements. Digital images suitable for our purpose were readily available for free from http://glovis.usgs.gov/ and http://deli.dnr.state.mn.us/ Therefore, we were able to access the two data images for 1984 and

3. Methods and procedures

In order to determine whether the WSRA of 1969 had positive impacts on maintaining vegetation cover on the Lower St. Croix River, we used a digital image taken relatively soon after implementation of the act and another after a good number of years after implementation of the act – that is the 1984 and the 2010 LandSat images. The 1984 image was used under the assumption that the implementation might have had little impact by then. Also, we chose to have twenty-six years between image acquisitions because we assumed that it is long enough to show any impact of the act on the land. Both images were taken in May to insure that there were minimal differences in the atmospheric effects on the images. The images were taken under 0% cloud cover.

5 3.1. Materials and tools

The materials we used included the following:

a) Two satellite images – the images were acquired using Thematic Mapper sensor by

LandSat 5 spacecraft in May of 1984 and May of 2010 respectively. The file name for

1984 is LT50260291984141XXX01, while that of 2010 is LT50260292010148PAC01).

Both images were downloaded from http://glovis.usgs.gov/ for free. The two images used

were cloud free, and thus guaranteed accuracy in image interpretation, and thus good

analysis. In addition, both were acquired at a scale of 1km. This resolution was

considered good enough for the purpose of determining land cover changes.

b) Shapefiles - the shapefiles were acquired from http://deli.dnr.state.mn.us/ for free. Three

shapefiles used in analysis include: the Minnesota county boundary shapefile; the St.

Croix River shapefile; and land ownership shapefile. The specific names of the files used

- St. Croix river shapefile

- Minnesota County Boundaries-layer name-bdry_counpy2 and

- GAP Stewardship 2008 - All Ownership Types-layer name-own_mnstwdpy2

c) Softwares used for analysis are ArcMap 10 Software and ERDAS Imagine 2011

Software. ERDAS Imagine 2011 was used to process the images, classify land cover, and

to determine land cover changes. On the other hand, ArcMap 10.12 was used to identify

our study area as well as making the thematic maps.

d) Google earth was used as an aid in classification of our study area in the two images.

6 3.2. Identifying Study Area

Due to the limited time we had to conduct our study, we only focused on an area 500meters away from the river, and only within Afton and Denmark Townships of Washington County. The

500 meters distance from the river was assumed as the area most effective for contributing to the quality of the water, and thus qualified to be in the easement program. The only areas included are those under private land category. Another more important reason for focusing on the private lands was that we assumed that unlike public lands, private lands are operated under profit, and thus they can be converted from one use to other uses whenever the owners see an opportunity to profit more from their land. We first acquired shapefiles from the http://deli.dnr.state.mn.us/and used ArcMap tools to extract only the areas that were relevant to our study. The following steps were taken to identify the study area:

 We overlay (using the union tool) the Minnesota county boundary shapefile with the St.

Croix River shapefile and then selected an area that intersects both the river and

Washington County. Using the “select by attribute” command in ArcMap, we selected

the river section found only in Washington County.

 We made a buffer of 500meters on the St. Croix River section found in the Washington

County to identify the likely area that may fall under the voluntary easement program.

 Using the union tool, we overlay the shapefile with 500meters buffer with the land

ownership shapefile to identify areas that were on private lands, but also within

500meters from the river.

 We further reduced our study area by clipping areas only found in Afton and

Denmark Townships using an empty polygon.

7 8 3.3. Land cover change analysis

The two images were both acquired from http://glovis.usgs.gov/, and were classified separately. In order to analyze our data, we did the following;

 We first stack the images separately before we opened them in ERDAS Imagine for

analysis.

 The two images (the 1984 and the 2010 images) were projected (from

WGS_1984_UTM_Zone_15 to NAD_1983_UTM_Zone15N) so that they matched with

our vector shapefile which comprised our study area.

 The identified study area (vector layer) was used to clip the 1984 and the 2010

raster layers to extract small portions of the images that comprised of only our area,

before they were classified.

 In most classes identified, at least 7 sites were included in training sites. In each

image, seven classes were identified (forest, agricultural land, grasses, Commercial,

developed – rural, and beach). The unclassified region is mostly empty pixels.

 After obtaining thematic maps for the two images, we applied the Matrix union tool

to show areas that have pixels that coincidence in the two images and thus obtained

a change map.

 We also applied the summary report of matrix tool to obtain the amount (in acres)

and percentages of land that has changed in each class.

4. Results and discussion

The results show that there is some land cover changes occurring in the area. Even though we could not determine the exact amount of land cover that changed to other land cover types (e.g. from forest to crop cover), we can see that there is an increase in rural development (from 10%

9 to 22%). In addition, there is a significant decline in forest cover from 29% to 21%. On the other hand, beach area seems to have increased, as it did not seem to be apparent in the 1984. These results do not provide a firm conclusion about the effectiveness of the WSRA of 1969, however, because the results may be flawed due to misinterpretation of some features. For example, the analysis shows that water cover has increased from 37% to 40% and agricultural land has declined from 12% to 7%. These results are almost impossible considering the known changes that have been occurring in the area. This misinterpretation of some feature may be largely due to lack of ground trothing during our classification, small study area, and poor resolution of images used. Overall, there is a decline in natural forest land cover in the area. Observed land cover changes include: from forests to rural development, from grassy areas to rural development, and from forest to impervious (beach area).

10 5. Conclusion and Recommendations

Based on the observed results, even though we do not have specific measurements of the changes, there is evidence that land cover has change. For example, land cover has changed from forest or grass cover to rural development, and from forest cover to impervious (beach area)

Based on the observed results, we recommend that there is need to conduct a more rigorous study to determine how much land has changed to other land uses to avoid future pollutions in the river. In addition, there is need to review the management plans of the Lower St. Croix

Riverway to ensure that the implementation of the Wild & Scenic Rivers Act (WSRA) of 1969 meets it objectives. Without implementing the recommendations above, it is hard to conclude on

11 whether the WSRA of 1969 and the scenic easement program have been effective at maintaining

or improving vegetation cover in the area.

References Cooperative Management Plan (2002). National Park Service Retrieved from http://home.nps.gov/sacn/parkmgmt/planning.htm

http://deli.dnr.state.mn.us/

http://glovis.usgs.gov/

Metropolitan Council (MET). 2009. Metro Stats: Population Growth on the Developing Edge: the Metro Area in 2009.

Minnesota Pollution and Control Agency (2012). “Lower St. Croix River Watershed Monitoring and Assessment Report”. Retrieved from http://www.pca.state.mn.us/index.php/view- document.html?gid=18468

http://www.metrocouncil.org/metroarea/MetroStatsPopulationEstimates2009.pdf

Wild & Scenic Rivers Act (1969): Public Law 90-541. Retrieved from http://www.rivers.gov/rivers/

12 Appendix 1

Figure 1: Map of Lower St. Croix Riverway showing Afton and Denmark Township areas (study area)