Abstract
The sediment release and deposition characteristics associated with sediment replenishment by outlet gate operation of check dam in the step-pool structured small stream (Kamogawa River in Fukuoka Pref.) were investigated. The basin was mainly consisted of sandy weathered granite and the check dam had been trapped 13,700 m3 of sediment in a mutual layer with sand and cohesive cray since establishment 29 years ago. After the gate opening on March 2017, approximately 12.1% of total sediment volume was immediately released and further 6.6% flowed out in the subsequent floods. Estimated suspended sediment (SS) concentration was reached to about 1200 mg/L in downstream. The sediment from upstream filled some pools in the steep section. It suggest that sediment release can influenced in change of land form and substrate characteristics even in the step-pool section.
