STUDY ON WIND CHARACTERISTICS AROUND MIDSTREAM OF THE YOSHII RIVER IN OKAYAMA IN WHICH THE TRADITIONAL TRAFFIC SYSTEM CALLED 'TAKASEBUNE' HAS OPERATED

In Yoshii river in Okayama, Japan that flows to Setonaikai through Wake town in a mountainous area, the traditional river traffic system using small boats called 'Takasebune' has operated, going upstream by wind sail through the narrow and twisty river course. This suggests that there was enough wind power to push boats upstream, and that some areas along the river course have stable and strong winds. Also, some records of the past suggested that it was able to sail all the year round. This study focused on the yearly mean wind velocity around a middle stream area in Wake town. Results of the surface wind observation revealed that 2m/s-3m/s wind that is influenced by a mountain and valley wind blows through the year. According to the simple wind field simulation, the Yoshii river valleys have unique geographical conditions that the wind from south or west flows into valleys relatively easily. Even the small wind velocity is not suitable for wind power generation, the wind field which the Takasebune used is applicable for environmental education of the natural power sources used in the past.