Using optical porosity to evaluate the shelter effectiveness of windbreaks in southern Ontario

This thesis is an investigation of the relationship between the optical porosity of a windbreak and the shelter effect found behind it. Relative windspeed reduction was measured behind nine relatively narrow, homogeneous windbreaks to assess whether any characteristics of the windspeed reduction curve generated could be predicted from optical porosity. The latter was determined for each of the windbreaks by digitizing high contrast black and white photographic silhouettes using the Oculus digitizing system. Various structural and environmental parameters were also measured.; The results suggest that optical porosity can be used to predict minimum relative windspeeds and may therefore be useful as a guide in the field evaluation of windbreaks. The regression results suggest that greater predictive accuracy could be achieved if enough data were obtained to develop species-specific predictive equations. The relationship derived in this study should be applied only to those windbreaks with characteristics similar to those described above. (Abstract shortened by UMI.)...