Land-Use in Loudoun County, Virginia

Rani Indela and Melissa Baccus

Fall 2016

ES 771 Remote Sensing

Dr. James S. Aber, Instructor

 ES 771 Remote Sensing Homepage

Table of Contents

Abstract

Pre Suburbanization

Post Suburbanization

Process

Analysis: Changes from 1985 to 2015

Conclusion

Bibliography

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Figure 1

Location of Loudoun County in Virginia.

Image by https://nationalmap.gov/ ,

Public Domain, https://commons.wikimedia.org/w/index.php?curid=1692442 

Abstract:

Loudoun County is located in the neck of Virginia between the Potomac and the Rappahannock River. See Fig 1 for location in relationship to Virginia. Between the 1940’s and 1960’s the population in Loudoun County remained constant at 20,000 people and the area was mostly agricultural use.  In the 1960’s the Dulles International Airport was constructed, Washington DC was growing and major roads in the area were being improved. These developments have drastically changed the land use in Loudoun County.  With the increase of suburbanization, the population has quadrupled in the last few decades (Loudoun County, VA and its representatives 2016).  See table 1 below for population growth by decades.

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        Table 1

Table created by Melissa Baccus and Rani Indela December 2016.

Source Data from https://www.census.gov/

Pre Suburbanization:

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Figure 2

Land use changes made to the Dulles International Airport area.

Panchromatic B&W Digital Aerial Mosaic Image.  

Image created by Melissa Baccus and Rani Indela, December 2016.

Source Images from: https://logis.loudoun.gov/archive/ 

Public use with acknowledgment of USDA FSA and Loudoun County.

Before the 1980’s Loudoun County land use was 37.7% agricultural and 36.9% forest areas.  Major developments in the southeastern part of the county have drastically changes the land structure of this county (Auch 2012).    See Figure 2 above for land use changes made to this area over the last 60 years.  Figure 3 below is a false composite image of Loudoun County.  The green in the image is vegetation, gray land and dark purple is man made structures.  By 1985 a small portion of the county was becoming urbanized.   Figure 4 below indicates the land uses at this time.  Concerned with the environmental quality of Loudoun County the Agricultural and Forest District Program was formed in 1979 to protect agricultural and forest areas. The county was one of the first in the United States to use GIS to study and monitor land use (Scheel 2011).

1985NDVIFALSECOMPOSITE.jpg

Figure 3

NDVI False Composite of Loudoun County, Virginia.  

Image created by Melissa Baccus and Rani Indela, December 2016.

Landsat image using bands 2,3, 4 and 5.

LANDUSE-1985.jpg

Figure 4

Land use of Loudoun County, Virginia.  

Image created by Melissa Baccus and Rani Indela, December 2016.

Landsat image using bands 1,2,3, 4, 5,6  and 7.  

Post Suburbanization:

        From 1990 to 1997 the population in Loudoun County grew 55%, and with that growth the agricultural and forest areas dropped to below 15% of the county.  The population has continued to grow quadrupling the last few decades.  In figure 5 below the dark purple coloring (man-made structures) shows how the urbanization has increased and figure 6 indicates the current land use for this area.

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Figure 5

1990-2015 NDVI False Composite of Loudoun County, Virginia.  

Image created by Melissa Baccus and Rani Indela, December 2016.

1990-2010 Landsat image using bands 2,3, 4, and 5.

2015 Landsat image using bands 3, 4, 5 and 6.

LANDUSE-2015.jpg

Figure 6

Land use of Loudoun County, Virginia.  

Image created by Melissa Baccus and Rani Indela, December 2016.

Landsat image using bands 1,2,3, 4, 5,6  and 7.

Due to the major land use changes, several programs are initiated for GIS to study the effects of this region.   These land changes can affect the hydrological and nutrient dynamics of the rivers downstream.  A current study is looking at the changes in urban area, forest land, water body and vegetation/grassland in Loudoun County.  Most of the loss has occurred in the eastern part of the county and in other areas of the county forest fragmentation has increased.  For example the Direct to Potomac area has increased by 306 more fragmented areas.  Also, the tree species population has changed suggesting a transition from farming to other types of land use.  As farmland is abandoned eastern cedar and Virginia pine regrow.    These fragmental forests can influence the thermal structure of the area.  With the increase of buildings, roads and parking lots the thermal temperature also increases.  These change could lead to other climate changes for the region (Fuller 2001).

Process:

The current study is looking at the changes in urban area, forest land, water body and vegetation/grassland in Loudoun County. This study is limited to the availability of remote sensing images. The first clear image available to download  is in September 15th, 1985. The latest clear image used in this study to compare with previous image is August 17th, 2015.  The 1985 image data were collected in 7 bands, but  2015 image collected has 11 bands of data.

IDRISI software was used to process the image data. The false composite image for 1985 was created using. The NDVI image for 1985 was created by using bands 3 and 4 and the NDVI false composite image was created using bands 2,3,4 and 5. The NDVI image for 2015 was created using bands 4 and 5 and NDVI false composite image was created using bands 3,4,5 and 6. The NDVI and false NDVI composite images were created for every 5 years from 1985 to 2015. This study compares only September 15th, 1985 image with August 17th, 2015 so the rest of the images are not shown in this study. The images for 1985 and 2015 were then clustered and isoclustered to differentiate the urban, forest, vegetation and water body. The images were then reformatted to Loudoun county and saved with map composition for both years. The clusters in the image is calculated for the area in square kilometers.

Analysis: Changes from 1985 to 2015:

The urban area is increased to 1233 sq km (urban land + Semi-urban land) in 2015 from 670 sq km in 1985. The increase in urbanized land use is 563 sq km.  The forest patch has been decreased from 913 sq km to 477 sq km. The decrease in forest patch is 436 sq km. The water body is decreased from 31 (water body + shallow water body) sq km to 20 sq km. There is no significant change in water body. The vegetation is decreased from 556 sq km to 355 sq km which is a significant change.

Note: The changes are calculated based on the clusters created by computer without any field study. Six clusters are created by isocluster command from approx 20 clusters of the image, so there might have been some compromise in creating the accurate data. The separated clusters might have some similar or dissimilar clusters. Therefore, the calculated area in the image may not be accurate.

Conclusion:

        The land use of Loudoun County  has changed significantly from 1985 to 2015. The major land is used for residential and commercial purposes. The main purpose of this study is educational and to analyze urban area, water body, forest patches and vegetation areas approximately. This project could be further used to analyse the sustainable development.

Bibliography:

Auch, Roger F., Darrell E. Napton, Steven Kambly, Thomas R. Moreland, and Kristi L. Sayler. 2012. "The Driving Forces Of Land Change In The Northern Piedmont Of The United States." Geographical Review 102.1: 53-75. Print.

Fuller, Douglas.2001. "Forest Fragmentation in Loudoun County, Virginia, USA Evaluated with Multitemporal Landsat Imagery." Landscape Ecology 16: 627-42. Print.

Loudoun County, VA and its representatives, 2016, "Live Edit." Loudoun County, VA - Official Website - History. CivicPlus Content Management System, Accessed online. <https://www.loudoun.gov/index.aspx?nid=174 >Web. 25 Nov. 2016.

Scheel, Eugene, 2011, Loudoun County GIS Day, “The Evolution of a Community” Accessed online. <https://www.loudoun.gov/index.aspx?NID=1639 > Web. 25 Nov. 2016.