THE SEDIMENT MOVEMENT DUE TO THE RECONSTRUCTION OF NIKARYOU-SYUKUGAWARA WEIR IN TAMA RIVER

Abstract

The purpose of this study is to show the effects of the sediment movement due to the weir reconstruction.
Nikaryou-syukugawara weir in Tama River was reconstructed and the weir crest level was dropped about two meters in order to increase the flow sectional area. After the weir completion in 1999, a lot of sediment in the upper reaches of the weir ran off with two floods. It was found through the monitoring data that the flow sectional area in the upper reaches increased due to the sediment run-off. In the lower reaches of the weir, it was found that the harden-silt bed was gradually covered with gravel and that some scour holes were to be shallower. The sediment movement mentioned above is favorable for the river maintenance. A 2D numerical model was applied to the prediction of the sediment movement and it was found that the model is useful.