Impact on flood level in Puyang river caused by river bed changes of Qiantang estuary

The Puyang river located in Zhejiang province is a principal river for flood control,but its flood is difficult to discharge owing to the tidal backwater in Qiantang estuary.Recent years climate changes and human activities caused a considerable change in the river bed and flow channels of this estuary and consequently an obvious flood level rise from 0.22m to 0.89m at the Wenyan station.These changes have produced severe impact on flood-discharging capacity of this river.Based on analysis on multi-years river-bed evolution of Qiantang,this paper adopts a two-dimensional numeral model to simulate the flood level in Puyang under two bed conditions,river bed averaging up to 1997 and averaging over recent years.Results indicate that under a flood of return period 100 years in the estuary,flood level rises at the Meichi and Linpu stations of Puyang are(3~4)cm and(4~5)cm,respectively,and(17~30)cm and(34~76)cm under a flood of 5 years.These shed some light on the great impacts by the estuary change.