New Development of Sediment Flushing Technique

The coordinated flushing at Dashidaira and Unazuki reservoirs on the Kurobe River in 2001 and 2002 and sediment flushing of the Lower Yellow River in July 2002 are introduced in this study. The differences between the two types of flushing and conventional flushing are analyzed. The environmental impacts and relevant mitigation measures of the sediment flushing are discussed. The coordinated flushing has less impact on the downstream environment compared with the flushing at only one dam. The sediment flushing of the Yellow River performed in July 2002 is the first flushing experiment in the world to wash away the sediment deposited in the riverbed. The measured results show deposits of 36.2 million ton was scoured from the bed of the Lower Yellow River. The flushing of the Yellow River has no severe negative impact on the downstream aquatic lives. The flushing of the Yellow River expands the concept the sediment flushing and the concerted flushing at Dashidaira and Unazuki dams shows an environmentally friendly flushing example. The major difference between the flushing at a reservoir and the flushing of a riverbed is how to manage the reservoir operation.