A temporal study of urban development for the municipality of Anchorage, Alaska

Abstract

A land use/land cover database was produced for a portion of the Municipality of Anchorage, Alaska to document the temporal and spatial extent of urbanization to assist in the analysis of changes in impervious cover and water quality. Data were derived from black and white and color infrared aerial photography, and satellite imagery from the early 1970's to 2000 in roughly ten‐year increments. Aerial photographs and satellite data were manually interpreted to identify and map land use/land cover classes which were then entered into a geographic information system, attributed, and georeferenced to a U.S. Geological Survey topographic map base. The spatial extent of the study was 31,117 hectares. In the early 1970's, approximately 7,356 hectares (24%) of the study area were mapped as urban developed. During the 30‐year analysis period, the largest increase in urban development occurred between the late 1970's and early 1980's when urban area increased to 12,263 hectares (39%). Between 1980 and 1990, and 1990 and 2000, urban area increased to 12,762 hectares (41%), and 13,980 hectares (45%) respectively. Most development occurred in forested or tall shrub areas, although some also occurred in wetlands. Between 1970 and 2000, close to 1,300 hectares of wetlands were lost due to development. Contrary to this, the amount of lake and pond area increased slightly from 261 hectares in 1973 to 334 hectares in 1980, and reduced to 310 hectares by 2000. The increase was primarily due to the filling in of gravel pits with spring melt water.