Modeling of long-term fluvial processes in the estuarine zone——Taking Feiyun estuary in Zhejiang Province as an example

A model for the long-term fluvial processes in the estuarine zone has been set up based on hydraulic geometry of river channels.The model has been calibrated by using hydrographic field data as well as data on historical morphological changes of Feiyun estuay.After the calibration,the model has been applied to investigate the impact to the change of flow discharge due to the construction of reservoirs in the upstream and the land-reclamation / bend cut-off project on the Feiyun estuary.The morphological development in the Feiyun estuary appears to be strongly influenced by the upstream flow discharge.A systematic decrease of the flow discharge will cause sedimentation in the estuary.According to the model results the river regulation will cause sedimentation downstream of the project site due to decrease of the tidal volume.In the upstream of the project site sedimentation occurs in the first phase and erosion in case of bend cut-off.The morphological responses of the estuary to both considered cases involve multiple morphological time scales which are corresponding with their spatial length scales.The smallest time scale related to the local changes of the project is as small as only about one year.