Extreme wind over a pine coastal forest established for sand-control at Aoyama of Niigata in Japan

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Ten-minute mean windspeed, maximum windspeed (gust speed) and the corresponding directions above the top of a sand-control forest of Japanese black pine (Pinus thunbergii Parl.) were recorded continuously over a 20-month period. The maximum 10-minute windspeed recorded was 13.0ms-1; prevailing wind direction ranged 145-180 degree north true. Gust factor changed with mean windspeed in linear function, and averaged at 1.92. The profile parameters of roughness length and displacement height over the sand-control forest canopy averaged at 0.52m and 5.6m. The cumulative distribution of windspeed was found to follow the Weibull distribution over the sand-control forest. The coefficients of the two-parameter Weibull model were k=1.36 (an exponent) and c=2.56ms-1 (a constant). According to the method developed by building design purpose, the parameters of Gumbel distribution (Type I extreme value) for describing the conditional cumulative distribution of the annual extreme (10-minute mean windspeed) were estimated. The most likely extreme windspeed over the sand-control forest in a 50-year period was calculated to be 14.2-15.7ms-1. Relationships between mean windspeed and gust factor showed that the data were normally distributed about the gust factor versus the regression line of mean windspeed. The relationships can be used to estimate the probability that a gust speed of given wind magnitude will be equaled or exceeded during a period when the mean windspeed is known. The results obtained in this study are very useful in understanding the general wind regime over the sand-control forest areas. It can be concluded that these observations are important for the establishment and management of the sand-control forests nearby the sea because there were few long-term measurements in the strong blown sand areas.

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  • 砂防学会誌

    砂防学会誌 54 (1), 12-20, 2001

    Japan Society of Erosion Control Engineering

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