Monday, January 31, 2011

Urban Growth and Change

As many of us know more people are now living in cities than ever before. Over half (3.3 billion people) of the world’s population are located in urban areas and this proportion is predicted to increase to over 75 percent by the year 2100 (United Nations, 2007). What I find most interesting is that while cities are growing they are also constantly changing.

The reason I bring this up are twofold. First I recently stumbled upon a site from the NY Times entitled "Mapping America: Every City, Every Block" which shows data from the US Census Bureau's American Community Survey from 2005 to 2009. What is interesting is that there are several maps showing the distribution of racial and ethnic groups throughout the US along with the percentage of foreign born and how neighborhood have changed over time (similar work is also being done at CASA for the UK's population). Such data could come in handy for residential segregation models.

Secondly, as cities grow, the question is where will such growth occur or in some instances where will urban areas decline (e.g. urban shrinkage). Recently we started using GeoMason to explore urban growth using the SLEUTH model as our basis. In the movie below we explore a simple growth scenario around Santa Fe, New Mexico. The model, like the original has the 5 growth coefficients (Dispersion, Breed Spread, Slope, Road) which affect how the growth rules are applied. We also implement the same growth rules (that of Spontaneous Growth, New Spreading Centers, Edge Growth,Road-Influenced Growth) as described on the SLEUTH website. The only thing missing from the model is the self modification procedures during the run time of the model. Data for the model comes a variety of sources including the National Map, the New Mexico Atlas and ESRI.