Vegetation and Land Cover Change in the Willamette River Greenway in Benton and Linn Counties, Oregon: 1972-1981

Abstract

Change in vegetation and land cover was determined from a time sequence of aerial photographs. Riparian vegetation and land cover in the legislatively defined Willamette River Greenway was classified as: Coniferous Forest, Tall Deciduous Forest, Low Deciduous Forest, Narrowleaf Shrub, Broadleaf Shrub, Grassland, Sand/Gravel Bar, Agriculture, Development, and Water. These types were mapped at 1:12,000 on a set of 29 sheets based on 1976 natural color imagery. A second set of 29 vegetation and land cover change maps was drawn based on interpretation and analysis of 1972 and 1981 aerial photographs using five mapping categories: aggregated vegetation cover; agriculture; development (including sand and gravel operations); cobble, silt, and sand bar; and water. Total Greenway area studied encompassed 12,813 acres (5,185 hectares). A total of 726 acres (294 hectares) of aggregated riparian vegetation was converted to agriculture and development from 1972 to 1981. The legislatively mandated Willamette River Greenway program may not be an effective approach to protecting riparian zone resources.