Vegetation changes in the Willamette River Greenway, Benton and Linn Counties, Oregon, 1972-1981

Graduation date: 1983Presentation date: 1983-02-03The nature and extent of niparian vegetation change from 1972 to\ud 1981 in the Willamette River Greenway in Benton and Linn Counties,\ud Oregon was quantitatively investigated. The study was primarily by\ud aerial imagery analysis and associated field verification. A classification\ud of vegetation and land cover within the study area was developed\ud and employed in imagery interpretation. Vegetation cover within\ud the Greenway based on this classification was mapped at a scale of\ud 1:12,000 using 1981 color infrared and 1976 natural color imagery.\ud Two additional sets of working maps, each consisting of 29 sheets, were\ud prepared from 1972 and 1981 airphoto coverage respectively. Each set\ud portrayed total vegetation cover, agricultural cover, and urban/industrial\ud cover. Comparison of the two sets of maps facilitated completion\ud of a single set of vegetation and land cover change maps depicting loss\ud of vegetation at the expense of gains in agricultural and urban/industrial\ud cover within the Greenway.\ud Area in vegetation, agriculture, and urban/industrial development\ud was measured for 1972 and 1981 for Benton and Linn Counties and change\ud in each category determined. In Benton County a total loss of 436\ud acres of vegetation within the Greenway was found. This is about 8% of the total Benton County Greenway area of 5,505 acres. In Linri\ud County the total loss was 290 acres which amounts to about 4% of the\ud total Linn County Greenway area of 7,308 acres. Of the total Greenway\ud vegetation lost in both counties, 60% was in Benton County and 40% was\ud in Linn County. No gain in vegetation in the Willainette River Greenway\ud was observed. A net loss of vegetation to agriculture and development\ud was found in each county