The estimation of wind exposure for windthrow hazard rating: comparison between Strongblow, MC2, Topex and a wind tunnel study

Abstract

This paper compares five different methods of wind exposure assessment in an attempt to identify a method that could serve in windthrow hazard assessment. The candidate methods that were selected are: a wind tunnel simulation, two numerical models based on air flow behaviour (MC2 and Strongblow) and two empirical methods (Topex and Topex-to-distance). Best correlations with the wind tunnel results were observed with Strongblow and Topex-to-distance. For MC2, significant correlations were obtained at high windspeeds but not at lower windspeeds. Ranking of windiness by topographic position was identical for the wind tunnel, Strongblow and Topex-to-distance. Wind direction estimation by MC2 showed little sensitivity to topography, especially at higher windspeeds. This fact can be attributed both to the version of MC2 used and the conditions in which the simulations were performed. The estimation of windspeed by direction obtained with Strongblow also appeared not to be very reliable. The satisfactory performance of Topex-to-distance and the ease with which this method can be calculated would make it appropriate for inclusion in a windthrow hazard rating system.