Association of Bay Area Governments
(ABAG) - Central Valley IRP
GIS
Geographic Information System (GIS) analysis is identified in the
enabling IRP law as "…a crucial tool for use in determining the location
of Jobs/Housing Opportunity Zones." With this in mind, the IRP developed
an integrated GIS and process that could be used to select and evaluate proposed
Jobs/Housing Opportunity Zone locations.
The jobs/housing legislation (AB 2864 [Torlakson, 2000]) further required that the GIS component of the IRP State Pilot Project include:
Utilization of GIS in Jobs/Housing Opportunity Zone Selection
The ABAG-Central Valley IRP developed an integrated GIS that included
thirteen data layers, including general plan, brownfields, environmental and
habitat information, and urbanized areas. Each layer of information was collected
from local jurisdictions, counties, the councils of governments and other sources,
i.e. State and/or Federal agencies.
Once all the GIS data was gathered and integrated, IRP staff determined that the best way to utilize the GIS in the Jobs/Housing Opportunity Zone selection process was through "spatial modeling."
Spatial modeling is best described in a sequence of steps, as applied to this particular project:
1. Convert each data layer into a "measurement." Measurements were developed by reviewing the available data and determining how best to apply it in the context of the goals of the IRP. For example, the GIS layer "transit stations" was converted into a measurement through the use of "distance from", i.e. one-quarter, one, and three-mile buffers. This measurement is linked directly to the IRP goal of developing jobs or housing near transit.
2. After measurement devices were identified for each layer, a threshold was applied to each measurement. The purpose of the thresholds was to establish maximum or minimum requirements that each Zone must meet. For example, with the transit station measure, the threshold was set at one quarter, one and three miles. Three miles was the maximum distance used for this particular measure. As with the measurements, the thresholds were designed to ensure that the Zones meet the intent of the IRP Pilot Project.
3. Assign numeric values to the thresholds developed in Step 2. By assigning values to the individual thresholds, geographic areas are in turn "valued" according to how well they meet the assigned thresholds. For example, those areas that are within one-quarter or a mile from a transit station are given a higher value than those areas three miles or greater from the same station.
The key to spatial modeling is the ability to add multiple GIS layers together to create a single GIS layer. By adding the layers together, with their associated thresholds, different geographic areas can then be categorized as to how well they meet established criteria.
Used in this way, the IRP's GIS spatial model was useful in determining optimal geographic areas for locating Zones. Spatial modeling also allowed the IRP to use GIS in scoring the individual Zone applications.
Further Information
For further information about the ABAG-Central Valley's use of GIS
in its program, please contact IRP staff at (510) 464-7900 or visit their website
(website opens in new browser).
Inter-active Mapping Tool (Link returns you to the main ABAG-Central Valley IRP page. Choose one of the map services available for interactive GIS.)