Coastal processes and tidal flat reclamation in Cixi City, China

The geomorphic configuration of hilly land (in the southern area), sea (in the northern area) and littoral plain (in the middle area) within the overall area of Cixi was formed about 2500 BP. The Cixi tidal flat belongs to the silting-up class of tidal flat. Eleven dykes have been constructed since the Song dynasty. The average outward migration rate of the coastline before the founding of the People's Republic was 25 m/a, and it has been increased to 50-100 m/a since the founding. The influencing factors for the formation and evolution of the Cixi tidal flat mainly include landform restriction, river runoff and human activities. The influence of human activities has become even greater in modern times. The principle for the regulation of the tidal furrow during the process of tidal flat reclamation should guide action according to circumstances as well as to reclamation of the tidal flat accompanied by the regulation of the tidal furrow. The former part of this principle means that the strike of the river channel must be in accordance with the law of stream movement and transport of sediment. The latter part means that the regulation of the tidal furrow must be closely linked to alongshore reclamation of the tidal flat.