Characteristics of river discharge and its indirect effect on the tidal bore in the Qiantang River, China

Abstract

Based on field data of river discharge, tide, tidal bore, and riverbed topography, the characteristics of river discharge, the effect of river discharge on riverbed erosion and sedimentation, and the feedback effect of riverbed erosion and sedimentation on the tide and tidal bore in the Qiantang River are analyzed. The results show that the inter-annual and seasonal variation of river discharge in the Qiantang River is noticeable, while the seasonal distribution of river discharge tends to be uniform after the construction of Xin'anjiang Reservoir. River discharge has a major effect on the erosion and sedimentation in the reach from Zhakou to Yanguan. There are laws of riverbed erosion in wet seasons and years and sedimentation in dry seasons and years. Relations in the Zhakou to Yanguan reach among the riverbed volume after the flood season, the mean and maximum river discharge during the flood season, and riverbed volume before the flood season are established. With the riverbed erosion from Zhakou to Yanguan, the low tide level decreases and the tidal range is amplified, and thus, the tidal bore is enhanced. The relation among tidal range, river discharge, and riverbed volume, as well as the one between the tidal bore height and tidal range is established on the basis of the field data. Furthermore, the variation range of tidal bores after the flood season is analyzed in wet and dry years. The indirect effect of the Xin'anjiang Reservoir on the height of the tidal bore is predicted and the mean height of the tidal bore from Zhakou to Yanguan decreases by 0.1–0.2 m.