1990-2000 Wildland-Urban Interface change in the U.S. West Coast

Contact: Volker C. Radeloff

Collaborators: Jason F. McKeefry, Sherry S. Holcomb, Roger B. Hammer, Susan I. Stewart, and Jeremy Fried

Our housing density change analysis used housing data from the US Census Bureau’s Topologically Integrated Geographic Encoding and Referencing (TIGER) dataset. TIGER provides housing, population, and other useful data in a convenient spatial format, and is available for both the 1990 and 2000 censuses. Because Census block geography changes between the years 1990 and 2000 in much of the country, however, it is difficult to track changes in housing density in the areas where this occurs. In order to conduct a meaningful longitudinal analysis of WUI change from 1990 to 2000, we developed a method to reconcile 1990 and 2000 Census block geography. Our objectives for this project are a) to reconcile 1990 and 2000 Census geography by apportioning 1990 housing units to 2000 Census blocks, b) to combine apportioned 1990 housing density and 2000 housing density with NLCD to identify WUI and non-WUI areas for both decades, and c) to map changes in WUI from 1990 to 2000 at 2000 Census block resolution. To achieve these goals, we apportioned 1990 housing units to 2000 blocks, weighting the distribution of the 1990 housing units according to the distribution of housing units in 2000. We then combined the output with vegetation data from USGS National Land Cover Data (NLCD), and calculated 1990 and 2000 housing density and percentage of wildland vegetation for each 2000 Census block. Census blocks in the vicinity of wildland vegetation could then be identified and classified as either WUI (intermix or interface) or non-WUI for both 1990 and 2000. Apportioning 1990 housing units to 2000 Census blocks reduces the occurrence of 'false declines' in housing density, i.e. areas where housing density appears to decline between 1990 and 2000 because 2000 blocks have a finer resolution than 1990 in these areas, and does so while maintaining the 2000 block geography, which is the most spatially detailed and accurate dataset available.

Acknowledgements:
This research was funded by the North Central Research Station and the Pacific Northwest Forest Inventory and Analysis Program of the U.S. Department of Agriculture Forest Service.

WUI definitions:
          Wildland-Urban Interface definitions