Characteristics of large woody debris transportation and deposition by
rainfall in the Kanaso Creek, Miyake Island
Kota KIKUCHI, Yoshiharu ISHIKAWA and Katushige SHIRAKI
Abstract
In this paper, we report the results of field measurement on transport and deposition
of large woody debris at rainfall in the Kanaso Creek, Miyake Island. Mud flows
and floods are prone to occur in the Kanaso Creek, because the watershed were
devastated by deposition of volcanic ash and affected by volcanic gas after the
eruption of Mt. Oyama in 2000. At the lower reach of Kanaso Creek, large number
of large woody debris were transported frequently at normal rainfall about 25mm/h
which occur several times every year on average. The number of transported large
woody debris was greater during high intense storm events. The maximum length
of large woody debris transported during the observed period was relatively smaller
than channel width. The maximum length of large woody debris deposited at the
upper of the Kanaso Creek. Percentage of deposited large woody debris with orientation
ranging from 60 to 90was two fold greater than values reported by Mizuhara (1979).