Abstract
After the 2011 Great East Japan tsunami, assessments of the role of coastal forests as natural defenses against tsunamis are strongly needed. To increase the reliability of such assessments, we conducted flume experiments using living branches of Pinus thunbergii that is main species in the coastal forests of Japan and measured the hydraulic characteristics of Pinus thunbergii. The drag coefficients of leaves decrease with increasing flow velocity in velocities less than 1.2m is and do not have an obvious relation to the flow velocity for velocities greater than 1.2 m/s. This may be because leaf deformation does not indefinitely increase as the flow velocity increases. Therefore, it is suggested that the drag coefficient of leaves converges with increasing flow velocity. For flow velocities greater than 1.2 m/s, the average drag coefficient of leaves is 0.013. The drag coefficients of branches do not have an obvious relation to the flow velocity and the average drag coefficient of branches is 0. 78.
https://ror.org/044bma518 
