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Remote Sens. 2017, 9, 71 3 of 17
areas. As a result, their composite spectral responses can introduce many uncertainties as well as add
confusion in long-term change detection. Thus, the objectives of this study were to:
1. Test our algorithm in a highly heterogeneous urban landscape to map the urban extent on a
yearly basis;
2. Quantify the patterns and trends of urban growth in NWA based on the generated urban
extent maps.
2. Materials and Methods
2.1. Study Area
Northwest Arkansas (NWA) is one of the most dynamic metropolitan statistical areas (MSA) in
the U.S. [24]. While NWA is comprised of four counties (Benton, Carroll, Madison, and Washington),
this study focuses on the two most heavily populated counties of NWA (Benton and Washington).
Within these two counties are four of the state's fastest growing cities, specifically Bentonville, Rogers,
Springdale, and Fayetteville oriented in a north to south linear direction (Figure 1). These cities are
bounded by the rugged Boston Mountains to the east and south while the gently rolling Springfield
Plateau characterizes the western portion of both counties.
Since the mid-1990s, considerable urban expansion within NWA has been driven primarily by
the influences of Wal-Mart Stores, Inc. (the world's largest retailer), Tyson Foods (the nation's largest
processor of chicken, beef, and pork products), J.B. Hunt Transport Services, Inc. (one of the nation's
largest freight shipping companies), and over 1300 suppliers and vendors drawn to the region by these
large businesses, NWA's economic climate, and its geographical location [25]. These three companies
alone boasted an estimated net sales of over 500 billion dollars in 2014 [26-28]. In addition to these
three economic drivers, the University of Arkansas, located in Fayetteville, has contributed to the
continual urban expansion within NWA through regular increases in student enrollment rates and is
considered to be the seventh fastest growing public university in the nation [29]. During the period
between 1980 and 2015, the total population in the state of Arkansas increased by 30%, doubling the
population in Washington County and tripling the population in Benton County (Figure S1).
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Figure 1. The Northwest Arkansas study area.
