SIMULATION OF COUNTERMEASURES AGAINST SEDIMENTATION IN A GORGE-TYPE RESERVOIR -A CASE STUDY OF MASAKI DAM RESERVOIR, JAPAN

摘要

A numerical model is developed for simulating the sedimentation process in gorge-type reservoirs. The model is a one-dimensional, uncoupled model consisting of parts for steady flow routing and sediment transport routing. It simulates the variation of reservoir bed profiles and formation of sediment strata accurately even under conditions of co-existence of sub- and super-critical flows and occurrence of rock-bed exposure. The present model is quantitatively specified to be applied to Masaki Dam Reservoir which was completed in 1976 at the most upstream reach of Katsuura River, in Tokushima Prefecture, Japan. As a result, the model is found to reproduce accurately the sedimentation process over the past 22 years since construction of the dam. The effective storage capacity of the reservoir has started to be actually impaired due to the sedimentation process progressing more rapidly compared with original prediction. Two types of countermeasures for improving deposition profiles are currently being considered; namely reservoir level control and sediment check dam construction. The efficiency of the countermeasures is quantitatively estimated using the numerical model presented in this paper.