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