LAND COVER ANALYSIS UTILIZING GEOGRAPHIC INFORMATION SYSTEMS AND HISTORIC AERIAL PHOTOGRAPHY: A CASE STUDY OF RIPARIAN ZONES IN THE LUCKIAMUTE RIVER BASIN, CENTRAL OREGON COAST RANGE

Geographic Information System (GIS) software and techniques were used to classify historic land-use regimes within the riparian zone of selected channels in the Luckiamute River Basin, central Oregon Coast Range. The Luckiamute drains over 800 sq. km. and is associated with a unique combination of geomorphic and land-use conditions that are well suited for the study of interdependent watershed variables. An archive of decadal scale USGS and USDA aerial photographs (1936, 1948, 1955, 1963, 1970, 1988,1994, 2000) were orthorectified and georegistered using Didger 4.0 and projected into the UTM Zone 10N coordinate system (NAD 1927). USGS digital raster graphics and orthophoto quadrangles served as known standards to provide control points for aerial photograph rectification. Affine and second order polynomial transformations consistently produced rectifications with RMS values less than 10 meters. For each year available in photographic archive, stream channels were digitized as polyline shape files using ArcMap 9.2. A riparian-zone bounding polygon was subsequently generated from the channel polylines using a 500-meter buffer that extended along the length of the respective photographs. Idrisi32 was used for preliminary raster classification of the riparian zones, followed by supervised polygon vectorization in ArcGIS. From this process, five land-use classes were identified: (1) cultivated land without forest canopy, (2) undifferentiated land without forest canopy, (3) sparse forest canopy, (4) moderate forest canopy and (5) dense forest canopy. The results of this methodology form part of ongoing research studies in the Luckiamute River Basin to identify controlling factors on invasive plant distribution, identify zones of anthropogenic disturbance, and design river restoration projects.