Assessment of Erosive Wind Frequency for Portage County, Wisconsin
File(s)
Date
1986-08Author
Behm, David H.
Publisher
University of Wisconsin-Stevens Point, College of Natural Resources
Metadata
Show full item recordAbstract
Erosive winds are those equal or greater than 18 mph (8 msec^ -1 ) measured at 33 feet (10 m).
March accounted for 15.4% of the annual erosive wind energy (EWE) for
Portage County, 10.6% more than observed in Eau Claire, WI. April
accounted for 18.1% of the annual EWE in Portage County, nearly the same
as that for Eau Claire (18.4%). The average maximum erosive wind
duration in April was 8.8 hours and the average maximum average wind
velocity (1-hour duration) was 28.5 mph (13 msec^-1). Climatic erosivity,
C, was calculated to be only 4%, compared to the 6% value presently used.
Soil erosion estimates calculated by the wind erosion equation with C=4
will generally be one-third less than those calculated with C=6.
Analysis of monthly and weekly erosive wind frequencies (March 15 through
December 15) identified critical erosion periods and those most likely to
result in abrasive flux damage to susceptible crops. In late May and
June the soil surface is susceptible to erosion because vegetative cover
is not yet fully established. This erosion can cause significant crop
damage to susceptible crop seedlings.
Prevailing wind erosion direction (PWED) was either west or southwest
throughout the year. During the erosive period (March 15 through
December 15) in Portage County, all preponderance values were less than
2.0, which indicates highly variable erosive wind direction. Reliance
upon only PWED and preponderance values to orient wind barriers is
unwarranted; other factors, such as frequency and direction data of
erosive winds during the critical erosive period, need to be considered.
Circular and curvilinear wind barriers are analyzed as alternatives to
traditional linear designs.