William Acevedo, Leonard Gaydos, Janet Tilley, Carol Mladinich,
Janis Buchanan,1 Steve Blauer, Kelley Kruger, and Jamie Schubert
U.S. Geological Survey
1 Johnson Controls World Services
Modern urbanization results in profound changes to the landscape, specifically the proliferation of asphalt and concrete along with the displacement of agriculture and forestland. A temporal database documenting urban land transformation is needed by urban and regional planners, policy and decision makers, earth scientists, and global change researchers to measure trends in urban sprawl, analyze patterns of water pollution and sedimentation, understand the impacts of development on ecosystems, and to develop predictive modeling techniques to forecast future areas of urban growth better.
The U.S. Geological Survey in collaboration with other agencies and Universities is mapping urbanization as it has actually occurred over time in selected metropolitan regions. These progressive geo-referenced databases of urban land use change are developed by merging information from historic maps, census statistics, commerce records, remotely sensed data, and digital land use data. USGS's rich 100-year topographic map, and 25-year Landsat satellite data archives provide the bulk of the source materials. Methodologies for interpreting, extracting, and compiling source information into each database have been developed. The local issues and concerns within a particular region will dictate the data layers that are compiled. Temporal thematic layers can include information on urban or built-up land, principal transportation, hydrography, agricultural lands, forest lands, wetlands, and population density.
These datasets provide the information necessary for geographic analysis of urban land use change. The historical perspective provides insight into the interactions between the physiographic and socio-economic variables which contribute to urban growth.
Mormons first settled in the Las Vegas area in 1855. In 1905 the town of Las Vegas was established by auctioning of land, and in 1911 the city of Las Vegas was incorporated. For the first part of this century Las Vegas was just a stop along the railroad. The first growth spurt occured in the 1930s. The construction of Hoover Dam on the nearby Colorado River was begun in 1931 along with the legalizing of gambling. The city of Boulder, Nevada was established to house construction workers.
The first hotels went up in the 1940's, both downtown and on what became known as the Strip. That decade saw the gaming industry blossom, putting Las Vegas on the map with openings of hotel/casinos like the Desert Inn, the Sands, Hacienda, and Tropicana.
In the 60's and 70's growth continued, fueled by tourism, and the nationwide migration trend towards the sunbelt. Hotels continued to attract tourists, and Las Vegas became a major convention center in the 80's and 90's. Las Vegas-style entertainment was broadened to include amusement park rides and attractions. Hotels became theme parks. The MGM Grand, Treasure Island, the pyramid-shaped Luxor, and the Stratosphere Tower were built. Several giant hotels/casinos/attractions are being planned along with the world's largest domed stadium, a huge expansion of the convention center, and a new monorail to whisk visitors from the airport to the Strip.
Population growth in the Las Vegas Valley was fairly slow during the first half of this century. But as the gaming and tourism industry blossomed, population growth began to increase rapidly. The population for Clark County was 48,289 in 1950. Las vegas accounted for 24,624 of the total. In 1960, Clark County's population was 127,016; Las Vegas 64,405.
In the 60's and 70's growth continued. By 1980 Clark County's population was 463,087; Las Vegas 164,674. Growth has been even more dramatic in the last several decades. Since 1980, population has more than doubled.
Today, the Valley's population tops one million, but that doesn't include the tourist population which itself is estimated at 582,000. It is the fastest growing metropolitan area in the country. One estimate is that the population will double by 2015.
As the city has grown, the land has subsided. In 1935 the National Geodetic Survey established a regional first-order level network. By 1963, the downtown area had subsided as much as 3.4 feet. By 1986, it had sunk another 2.8 feet. Comparable subsidence of the Strip is 2.9 feet and North Las Vegas 5.0 feet. The greatest threat is posed by continued growth of earth fissures. These have been mapped and found to be correlated with preexisting Quaternary geologic faults. Land subsidence is projected to continue as a function of ground water withdrawals. In recent years net withdrawals have exceeded recharge by factors of 2 to 3. This can only be alleviated by reduced dependence on ground water which would increase reliance upon already over-allocated surface water.
The built-up land data layer for Las Vegas provides a dramatic illustration of the spatial patterns and rates of change resulting from urban sprawl. The principle transportation data layer clearly demonstrates the influence that the transportation infrastructure (roads, railroads) have exerted on population development.