THE ESTIMATION OF WIND EXPOSURE FOR WINDTHROW HAZARD RATING - COMPARISON BETWEEN STRONGBLOW, MC2, TOPEX AND A WIND-TUNNEL STUDY

This paper compares five different methods of wind exposure assessment in an attempt to identify a method that could serve in windthrow haza rd assessment. The candidate methods that were selected are: a wind tu nnel simulation, two numerical models based on air flow behaviour (MC2 and Strongblow) and two empirical methods (Topex and Taper-to-distanc e). Best correlations with the wind tunnel results were observed with Strongblow and Topex-to-distance. For MC2, significant correlations we re 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 sho wed little sensitivity to topography, especially at higher windspeeds. This fact can be attributed both to the version of MC2 used and the c onditions in which the simulations were performed. The estimation of w indspeed 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 approp riate for inclusion in a windthrow hazard rating system.