UPlan is a rule-driven, ArcGIS software-based urban growth model suitable for rapid scenario-based modeling. Originally developed by researchers at the Information Center for the Environment (ICE) at the University of California, Davis, more than 10 years ago, UPlan is continually maintained by ICE and has been widely applied in California and adapted to planning needs in other USA states, as well as several international settings, including China, Egypt, and Kenya (see "From Urban California to Rural Kenya"). Input parameters, including urban growth attractions, discouragements, masks, and planning datasets, are easily collected and configured using UPlan. While not an explicit economic model, UPlan uses "attraction" and "discouragement" factors that score the attractiveness of each modeling grid cell to each kind of potential development, generally based on economic factors understood to drive land-use decisions. UPlan uses a raster, cell-based environment within ArcGIS for Desktop with the Spatial Analyst extension. The model is available online and free of charge (ice.ucdavis.edu/doc/uplan/download).
The basic assumptions of UPlan are the following:
UPlan allocates growth into each land-use category based on demographic inputs, such as average household size, employees per household, and the percentage of housing development going into specified densities of residential or employment categories. Three primary factors determine where each land-use class will be allocated: city and county general plans (or comparable boundaries indicating where future growth types may be allocated), areas where growth is prohibited (masks), and site development attraction and discouragement factors. Attraction and discouragement factors are representations of physical, political, or economic effects that make a particular location either more or less attractive for future growth of a given land-use category. First, areas permitted to each land use under the general plan are identified. Then, areas with other growth prohibitions (lakes, very steep slopes, publicly owned lands, or existing development) are removed from the available space. Finally, the attraction and discouragement factor values are established for the remaining cells based on a location's potential suitability for growth. These values permit systematic prioritization of development within the UPlan model for each land use, resulting in an attraction grid. This is a purely additive process, with user-weighted attractions adding values and discouragements subtracting values. Population growth allocation occurs on a raster cell basis starting with the highest-value net attraction and working incrementally downward until either all the available land has been occupied or all the demand has been met.
Currently, about one-quarter of the 58 counties in California are using UPlan, many with technical support from ICE staff. In particular, rural counties rely on UPlan for their planning process as part of the California Rural Blueprints process, which is a long-term public visioning exercise run by counties and regional planners and funded by the California Department of Transportation. In California, UPlan has proved to be an effective and popular tool for visualizing future growth in part because it is adaptable, it runs quickly, and the assumptions are transparent. Problems in implementation have risen where political will is lacking, access to high-quality data is difficult, and personnel resources are limited.
UPlan lends itself well to the geodesign concept based on Carl Steinitz's framework. ICE is currently working with several counties to help them revise their planning process using a geodesign approach, with UPlan serving as a tool for developing alternative scenarios and iteratively evaluating the impacts of potential future growth outcomes on such features as wildlife habitat corridors, agricultural lands, water resources, and transportation needs.
See also "From Urban California to Rural Kenya."