Quantitative progress in the evaluation of the wear of wooden check dam elements: case study of Aomori cypress wood 64 years after construction

Abstract

There are only few cases where the wear of elements of wooden check dams installed in a mountain stream has been investigated, and the actual state of the progress of wear has not been clarified. The purpose of this study was to clarify the progress of wear on the elements of the wooden check dam in flowing water. A wear survey was carried out on the elements of the wooden check dam in the Tsubokesawa basin, Aomori Prefecture, 64 years after construction, and compared with the wear progress after 51 years from the authors' survey in 2005. As a result, the influence of wear on the side surface of the elements appears remarkable and considering the change in flow rate from normal times to the time of water discharge, the elements were worn in three dimensions including the tip. When the residual ratio of the cross-sectional area was calculated, it was about 40% at the end of 51 years, but it became clear that wear progressed to about 30% after the end of 64 years. Even though only the heartwood of Aomori cypress wood remains, in 13 years, 9–15% of the cross-sectional area is still wear by the flow of water containing sediment sand, and it was considered that the wear was in progress.