Flood characteristics at Qiantang River Estuary

The Qiantang River Estuary is a strong tide estuary. The large volume of incoming water from the river basin and the high tidal level on the lower Qiantang River might result in high water level along the river. For about half a century, the construction of reservoirs on the upper Qiantang River has brought floods in the river basin partly under control, and the large scale reclamation at the river estuary has improved the stability of the river channel. However, the characteristics of response to flood and tide along the river have changed in a certain degree: reservoirs on the upstream have stopped some weak floods, resulting in the decrease of the river capacity before the flood season; large scale reclamation has narrowed the river channel and strengthened its reflection of tidal waves, the impact spreading to the mouth of the Hangzhou Bay; the overflow section of the river channel has decreased, the mean high tide level at Hangzhou City in 1990s being nearly 50cm higher than that in 1980s, and the number of times that the highest water level exceeds the warning water level having doubled once in ten years since 1970.