Urban Growth Along the Highway 50 Corridor 1988-2006



Author

Randolph Battersby
American River College, Geography 350: Data Acquisition in GIS; Fall 2008
xbattersby(a)hotmail.com

Abstract

This paper explores the development that has taken place over an eighteen year period along the Highway 50 corridor from the Sacramento county line to Placerville. The pattern of urban growth is analyzed using GIS software, looking for signs of governmental influence and general trends. Urban growth is quantified and represented by a choropleth map. The Scenic Highway designation is found to have had a negligible effect on urban growth when compared to other forces in the region.

Introduction

U.S. Highway 50 is designated a Scenic Highway in El Dorado County. This designation may serve as barrier to development along the highway itself, especially if the Scenic designation is desirable enough that local governments strive to maintain it by suppressing growth in the area. But what happens in the surrounding area? Has the Scenic Highway designation tended to force more development to occur just outside its borders? Has urban growth overall followed an intelligent plan?

Background

The value of developed land is obvious. It serves as our homes, places of work, transportation networks, entertainment venues, and more. The intrinsic value of undeveloped land may be less obvious in our everyday lives, but it can be equally important. Whether they provide food, as in the case of farm and grazing lands, recreation opportunities, or habitat that supports wildlife, non-urban areas are vital to our existence even though they may be rarely experienced directly by the typical city dweller. Being geographically separated from the open space can make it difficult for an urbanite to keep track of changes to the landscape which may eventually impact him.

Concerns over chaotic growth spurred the adoption of master growth plans in many American cities around a century ago. These master plans were largely voluntary and not enforced unless a group of citizens aggressively insisted upon it. The very constitutionality of zoning laws was questioned until the historic 1926 Supreme Court decision of Euclid v. Ambler (Hall, 1996). In 1937, the state of California passed legislation requiring all cities to adopt master plans. Over the next three decades several specific elements were required to be added to master plans, and “general plan” became the preferred nomenclature. In 1969 Ian McHarg published his book Design with Nature which tied planning to the natural environment. Also in this year the Sacramento Area Council of Governments (SACOG) grew to a regional size on par with what is today, although it was then called the Sacramento Regional Area Planning Commission. The multi-county sized regional boards are necessary to address issues such as transportation networks, land use, conservation, and open space.

The first version of the modern Geographic Information System (GIS) was created in 1962 for the Canadian Department of Forestry and Rural Development. It was created to facilitate the management of resources and land use on a national scale. Today, GIS is an integral component of urban and regional planning. Most modern GIS software does not require a specialized workstation and will work on a typical desktop computer. While it is true that the price of these software packages will prohibit their widespread adoption among home users, there is a plethora of data, information, and maps available to American citizens for nothing more than the cost of an internet connection. The available databases are constantly growing and, with the digitization of historic maps, make it possible for the average citizen to visualize changes in his region over time, “check up” on how effective planning seems to have been, and perhaps even peer directly into the history of planning and see some examples of the results of poor planning.

This paper is an example of how a citizen with minimal training (much of it available online) can acquire data relevant to land use in an area and create from it a visual and quantitative analysis of land use changes.


Methods

The Farmland Mapping and Monitoring Program (FMMP) was established under the Division of Land Resource Protection in 1982 to fill the critical need for data on the nature and extent of California’s farmland. It was formed in response to decreased funding for the USDA Natural Resources Conservation Service’s work on mapping national agricultural resources. The FMMP classifies farmland as prime, unique, of statewide importance, or of local importance. It also has classifications for grazing land and urban/built-up land. These FMMP county land use maps were the base layer for this analysis. They were downloaded from ftp://ftp.consrv.ca.gov for the years 1988 and 2006 (the most recent set available).

The FMMP maps cover the years 1984–2006. The original intent of this study was to examine regional growth changes over the last 20 years. This was not possible as 2008 data are not available yet, and data were not collected for Sacramento County in 1984 or 1986. Using the earliest available Sacramento County data, the years covered are 1988-2006. The maps are available in ESRI shapefile format.

The maps for El Dorado County and Sacramento County were loaded into ESRI ArcMap 9.2sp6. The combined map used a California Alber’s equal area projection, NAD 1927 datum, and Clarke 1886 spheroid. A geodatabase was created and the shapefiles were dissolved down to county boundaries, urban areas, and non-urban areas. These were converted to geodatabase feature classes. The non-urban areas included farmland, grazing land, and low density rural housing. Urban and built-up areas were defined using the FMMP definition of land containing structures with a density of at least 1 unit to every 1.5 acres. Other developed uses such as golf courses and landfills were included in this category.

Shapefiles containing major roads and geographic place names were downloaded from the California Spatial Information Library (CaSIL)6:00 AM 12/17/2008 and projected on the map. A shapefile containing California lakes was located using the California Environmental Information Clearinghouse (CEIC). The file was stored on Dept. of Fish and Game servers and linked to directly from the CEIC portal.

A buffer zone was created around a 28 mile section of Highway 50 stretching from the Sacramento county line to Placerville, where the Scenic Highway designation begins. This defines the study area. The buffer stretched 6 miles in all directions, including eastern Sacramento County. The 6 mile zone was chosen empirically, covering developments that were easily visible while driving on Highway 50. In many areas the extent of the buffer is not visible from the highway and, naturally, in other areas the buffer is only a small portion of the visible landscape. No attempt was made to create a line-of-sight coverage area around the highway.

The layers of the study map were then arranged so that the extent of the urban areas could be seen for both 1988 and 2006. It was assumed that there was not any substantial loss of urban area during the study years, and this was verified visually during construction of the map. The urban area polygons that extended beyond the study zone were bisected using the Clip geoprocessing function.

The areas of the urban polygons within the study zone were summed in tables using the attribute Summarize function. The 1988 area was subtracted from the 2006 area and the result was divided by the 1988 area to yield a growth rate figure.

Results

The areas of urban land are presented in the table below. El Dorado County experienced growth of 44% during the 18 year period studied. Sacramento County experienced 155% growth. The total study area grew 63% overall.

Urban Area in Acres El Dorado County Sacramento County Total Urban Area
1998 16,706 3,480 20,186
2006 24,050 8,906 32,956
Growth Ratio 0.440 1.559 0.633




Figure 1
Urban Change

Analysis

It was obvious as soon as the first draft of the map was complete that the Scenic Highway designation had a negligible effect on urban growth in the region. There were much stronger pressures directing growth towards the western border of El Dorado County, or perhaps inhibiting growth in the entire Placerville area. Growth along the Scenic Highway portion was not quantitatively compared to the non-scenic portion as it fit within the overall trend of growth dropping off as distance from the Sacramento county line increased.

The most surprising statistic to emerge from this study is that eastern Sacramento County, specifically the Folsom area, has experienced more than 155% growth over the last two decades, more than triple the rate of El Dorado County for the same time period. Folsom is a logical area to concentrate growth, having relatively easy access to the city of Sacramento and its developed suburban areas. Folsom has also greatly increased its own retail and industrial resources during this time period, so growth in this area does not necessarily equate directly to an increase in commuting. Growth in areas farther from Sacramento, like El Dorado Hills and Cameron Park, is much more likely to generate a commensurate increase in commuter trips, as the job base outside of Sacramento County does not appear to have increased as rapidly as housing has. Whether or not the observed growth pattern constitutes “smart growth” is outside the scope of this paper. The document presented here is the first step in an independent evaluation that could include investigating overall adherence to the general plan, how amendments to the general plan have the changed the landscape, or how long transportation infrastructure has lagged behind traffic needs.

The total measured area of the counties varied from year to year by less than 5 square meters. The accuracy of the areas calculated should easily be within a 1 acre range.

The main problem in the acquisition of data for this project was not that it was in short supply but rather that is was so abundant that it was difficult to sift through. Extracting target data from large datasets was problematic at times. Using the current common broadband internet connection, downloading large datasets was relatively quick and easy. This was a very good thing, as several promising datasets turned out to be not very useful.

Another pitfall of collecting data from several different sources was that they were often projected in different coordinate systems. The datum and spheroid used varied depending on which California department was hosting the data.


Conclusions

Although the Scenic Highway designation did not turn out to have a substantial impact on urban growth patterns, it was interesting to see the extent of development presented on a map after having observed some of the changes take place.

In the current climate of wildly fluctuating energy prices, it is reasonable to expect that the demand for developments that are close to established infrastructure will increase greatly in value compared to outlying areas. This pattern of growth is already clearly illustrated in Fig. 1. The economics of commuting are likely to increase the pressure to develop the remaining open space in the Sacramento area, and this is something that landowners in the area may want to keep track of. A GIS provides a good way to do this, with the scope and level of detail tailored to fit individual needs.