The goal of this project is to assess the extent of urban sprawl into the rural areas surrounding Corvallis and Philomath, Oregon, which are located in Benton County, in the Willamette Valley, slightly west of the Coast Range. Sprawl in the valley threatens prime farmland, as well as forests in the foothills of the coast range. This project uses data from the 1990 Unites States Census to assess the distribution of demographic attributes commonly associated with sprawl; including large houses, high household income and property values, and non-gridded streets named for flora and fauna instead of numbers or presidents, as well as a comparison to more rural deomgraphic attributes, such as households that receive farm-based income. Unfortunately, data for the 1980 or 2000 census were not available for comparison to demonstrate a rate of advancement for sprawl. What the 1990 data do provide is a set of indicators to show where sprawl appears to be starting, and where it is likely to continue. I have used two controls for this shortcoming; first, my own knowledge of the area based on having spent over 18 years of my life there, and second the inclusion of one large, mostly rural census tract that includes a small corner of Corvallis and a vast area south of the town that is mostly agricultural. This tract will act as a basis of comparison to the rest of the county, which is mostly rural.
Note: All data are from the US Census Bureau TIGER Data, except for the non-tract locator maps, which use ESRI data.
The location of Benton County within Oregon and Corvallis within Benton County can be seen below:
This map shows the Census Bureau's designation of urban and rural lands in the Corvallis-Philomath area tracts:
The above map was produced using the GeoProcessing Wizard's union function to determine whether there were any urban areas lying outside of city limits, or rural areas lying within. The former would be a sure sign of sprawl, and the latter would constitute lands most likely to be developed. According to the US Census Bureau, neither of these conditions occur within any of the Corvallis-Philomath area tracts.
Now to examine the demographic indicators of sprawl. First, we look at the age of the housing units. The map below shows the percentage of housing units in each tract that were built in of three different eras. Newer housing on the edge of the urban areas can be evidence of sprawl, but it is not a definite indicator.
In orer to distinguish sprawling suburban homes from newer in-town apartments, other indicators must be taken into account. The following maps compare household affluence based on the number of rooms, income, and number of vehicles per household.
The above maps reveal a definite trend towards large, high-income houses in the north-central portion of the Corvallis-Philomath area. That is also where many houses were built in the 1970s and 1980s, indicating that it is a recently urbanized zone. There are also many two-car homes in the north-central portion. Most of the homes with more than two vehicles are in the more rural and agricultural southern tract, which makes sense given the need for transportation in low-density conditions and on large land plots.
Below we look at households that earn farm income, a main indicator of the relative weight of rural lifestyles:
The farm income map shows the predicatable results: the tract with the most farmers is the large southern tract, and the other tracts with the most rural land also have relatively high proportions of farm income. The tracts with the least are all within Corvallis city limits, the lowest being the small downtown tract that borders the Willamette River.
Lastly, we examine a map of the streets in Corvallis and Philomath to look for signs of sprawl and land that may be targeted for development. A good deal of the open space on this map has probably been developed over the past ten years, especially in the southwest portion of the city and its outskirts, which are not shown on this map.
Again, the north-central portion of the city shows the signs of sprawl: the streets are not gridded; in fact they are curved, and many cul-de-sacs are present. There is also much open space on the west side of this, which I believe has since become suburbanized. In addition, the terrain where these winding streets are found is more hilly than the outlying farmland and the downtown area where older neighbourhoods, Oregon State University, the Hewlett-Packard Plant, and the commerical centres are found, meaning the land, if it is developed, is most suited for residential use.