The formation and evolution of the Xisan Tidal Furrow and the reclamation of tidal flats in Hangzhou Bay

The Xisan Tidal Furrow appeared as early as 1976. The major dynamic factor in the formation of the Xisan Tidal Fu urrow is the increase in the flood-tidal level near Xisan Gate and the extension of beach face accretion in An'dong, both of which originated from large-scale human activities. The inlet position of the Xisan Tidal Furrow has experienced four stages, i.e., swinging, stabilizing, moving eastward, and stabilizing, while the series furrow at the outside beach face is the main cause of the change in the scouring and silting of the Xisan Tidal Furrow. This article explains the causes of the Xisan Tidal Furrow's formation and its evolution, and proposes the guideline of "regulating the furrow and reclaiming the tidal flats by making the best use of local topography." On one hand, the river channel direction must comply with the regular pattern of the stream current and of sediment movements. On the other hand, furrow regulation and reclamation of tidal flats along the riverbank should be combined. We suggest that fill stone should be used and a rock dam built to completely cut the Xisan Tidal Furrow; this should occur when the Qiantang River basin has a wet year.