- Soil erosion is a major source of pollution in the
United States. Erosion can cause both on-site and off-site
damages. It has been argued that off-site damages are a
significant component of soil conservation benefits and are
currently not well known.
Off-site effects of soil erosion are uncompensated
externalities. Given significant external costs from
erosion, there may be potential for net gains in social
welfare from increased soil conservation.
The major objective of this study was to examine, and
where possible estimate, the off-site costs of soil erosion
in the Willamette Valley. The value of erosion was measured
in terms of increased production costs. These costs are
incurred by economic agents in offsetting the effects of
Six types of publicly owned enterprises were studied to
determine erosion damages and related costs. These were
municipal water supply, county and state road agencies,
navigation supply, water storage reservoirs, and
hydroelectric power plants. Of these enterprises, only water
storage reservoirs and hydroelectric power plants did not
incur substantial costs to offset the effects of erosion.
Municipal water treatment costs were found to be
significantly affected by erosion. A sediment damage
function for the water treatment process was estimated using
econometric modeling. The estimated coefficients relating
suspended sediment and treatment costs indicated that the
latter increased with an increase in river borne sediment. A
50 percent reduction in river turbidity experienced by the
treatment plant studied would decrease chemical water
treatment costs and sediment disposal costs by $4750 per
year or approximately $4.55 per million gallons of water
treated. A 50 percent reduction in sediment loads for the
entire Willamette Valley would reduce municipal water
treatment chemical costs by an estimated $231,000.
An average cost analysis was also performed. This
analysis indicated water treatment costs were $21.00 per
million gallons of water treated. Inference to total
municipal surface water supply in the Willamette Valley
yielded an annual average erosion cost estimate, from
natural and man made sources, of $1,052,000.
County and state road maintenance departments must
frequently clean drainage structures in response to sediment
deposition from erosion. Benton county road maintenance costs, for sediment removal, were estimated to be
approximately $222,000 per year in 1984 dollars. An
inference to all county road departments in the Willamette
Valley, yielded a total erosion cost estimate of $3,743,000
per year. State highway maintenance costs in the Valley due
to sediment front erosion were estimated to be $503,000 per
year in current dollars.
Sediment removal involved with maintenance of a
navigation channel on the lower reach of the Willamette
river costs an average of $270,000 per year, expressed in
Aggregate erosion costs for all these activities were
estimated to be $4,758,000 per year in current dollars. This
figure is equal to approximately $0.67 per acre and $432 per
square mile for the Willamette Valley. These findings
suggest that there exists potential for off-site benefits
from increasing soil conservation activities in the Valley.
However the economic feasibility of soil conservation
projects in the Willamette Valley depends on their
implementation costs as well as the on-site and off-site
benefits. Cost studies of other activities impacted by
erosion are needed to estimate the total off-site costs of
erosion in the Willamette Valley.