Georgia Coastal Counties Housing Density Analysis 1940 – 2030

The regional household density analysis was created for the project,
Visualizing Land Use Changes on the Georgia Coast.

Conducted for
The Georgia Department of Natural Resources, Coastal Resources Division

Conducted by
The Geospatial Technologies Laboratory at NESPAL, University of Georgia, Tifton Campus

April 2006

Overview and Methods
Recent changes in human settlement patterns, most prominent at the fringe of metropolitan areas and in rural regions with attractive recreational and aesthetic amenities, are a significant cause of anthropogenic landscape change in the U.S. (Theobald, 2001).  These changes in residential development patterns are substantially modifying regional ecology and require reassessment of land use planning and resource management policies (Hammer et al., 2004).  Recent studies have demonstrated that household density may be more informative than population growth in evaluating landscape change and formulating regional resource management policies (Radeloff et al., 2001).

Following methods described by Radeloff et al. (2001) and Hammer et al. (2004), U.S. Census data including 2000 blockgroup boundaries and structures reported by block group and by county was acquired.  In the 2000 Census respondents reported the year in which their residence was built. This information is known to be flawed because people will not report structures that have been destroyed and may misremember the year in which their houses were built.  However, some of this error may be addressed by using 1940 – 1990 census data in which structures were reported by county.  Essentially, the methods use household structures reported by blockgroup in 2000 to backcast numbers of structures in these areas by decade back to 1940.

The 2000 Census reported number of structures by block group by decade for 1940 to 1990 (SF 3, Table H34).  Census reports for the decades 1940 to 1990 reported number of structures by county.  The 2000 Census data were used to calculate number of structures in each county by aggregating block group data for structures built as reported for each decade from 1940 to 1990 (retrospective county structures).  Number of structures in the counties reported in the 1940 to 1990 Censuses was used to represent original census county structures.  The difference between retrospective county structures and original census county structures for each decade (1940 to 1990) was calculated to determine the difference in reported structures in county.  This information was used to calculate the percentage of structures underestimated by the retrospective estimates for each county for each decade 1940 to 1990, using the following structures difference fraction:

original census structures – retrospective county structures
retrospective county structures

Applying the percentage of difference in structures reported retrospectively and those reported in the original census by decade uniformly to each 2000 census blockgroup yields an adjusted number of structures by block group by decade.

Household projections to 2030 were generated using a linear projection based on percent increase in households between 1980 and 2000 (U.S. Census projection formula).  This method may underestimate household development if in fact past trends do not adequately represent future rates of development.  However, the database supports alternative projection assumptions.  The animation above demonstrates the results of the analysis of changes in household densities in the coastal region between 1940 and 2030.  The report of no households in large areas in 1940 is an artifact of the census data and the analysis methods.  Relating the household density study to the coastal landscape ecology may provide insights for resource management, regional planning and land development policies.

Citations
Hammer, R., et al., Characterizing dynamic spatial and temporal residential density patterns from 1940-1990 across the North Central United States, Landscape and Urban Planning, Vol. 69, pp. 183-199, 2004.

Radeloff, V., et al., Rural and Suburban Sprawl in the U.S. Midwest from 1940 to 2000 and Its relation to Forest Fragmentation, Conservation Biology, Vol 19 (3), pp. 793-805, 2005.

Theobald, D. Land-Use Dynamics Beyond the American Urban Fringe, Geographical Review, Vol 91 (3), pp. 544-565, 2001.

Acknowledgments
                Mr. Mario Giraldo, Graduate Student, Department of Geography
                Mr. Nick O’Day, GIS Technician
                Mr. John Prechtel, Data Librarian