The Measurement of the Irregularity of Urbanized Areas

Abstract

A measure of the irregularity of the boundaries of Urbanized Areas is presented. This irregularity is related to the extent of scattered development and urban sprawl. For all 486 Urbanized Areas in 2010, the index, ranging from 0 to 100, had a mean of 79 (very irregular) with the majority of areas clustering near this value. The distribution was skewed to the left with a smaller number of areas having index values approaching and even going below 50. Larger areas tended to have somewhat higher levels of irregularity. Urbanized Areas in the Northeast and South had the highest average irregularity while those in the West were lowest. For some large urban areas, the largest Urbanized Area does not encompass the full extent of what should be considered the urban area. A set of 59 large urban areas consisting of 1 or more Urbanized Areas is the focus of further analysis. The same patterns emerged with high irregularity, the distribution skewed toward the less irregular areas, and higher irregularity for areas in the Northeast and lower for those in the West. Irregularity increased with the land area of the urban area and was lower for areas growing more rapidly and for areas subject to barriers to the expansion of urban development. Population density was lower in more irregular areas and in a simple model, the irregularity index and population accounted for 2/3 of the variation in density.