Land Cover Changes in an Urban Watershed of the Puget Lowlands, WA, 1986-2002

The Puget Lowlands are the most rapidly changing ecoregion in the US, as a result of forestry management and urbanization. However, it is unlikely that the processes driving land cover changes are uniform across the entire Puget Sound lowlands. Forest management practices by vary by land owner, and urban land uses are usually spatially autocorrelated.  To better explore urban land cover changes in this ecoregion, we selected the Puget Lowlands of the Duwamish-Green watershed as a case study. Containing much of the industrial activity of the rapidly urbanizing Seattle Metropolitan Area, the Duwamish-Green has been extensively altered by past river re-plumbing and by dam construction and operation.   As a result, its flood regime and floodplain have been highly altered.  From our raster GIS analysis of land cover data (1986 to 2002), we found that 34,573 ha (49% area) changed land cover types.  Four of the five most common land cover changes are related to urbanization.  The most common transition was from vegetated to urban types, and the second most common transition was from urban to more heavily urban. Analyses at multiple scales may be needed to better understand human and ecological processes driving land use and land cover trends.