According to the design of high water level and high value determination, it is required to not flood the harbour area at high water level. In order to reduce the project cost, it is necessary to take into account the balance of the amount of excavation and filling in the port area. At the time of expansion or reconstruction of the port area, the front elevation of the wharf should be adapted to the inland area of the original port area to facilitate the operation of road and railway vehicles. Each pier in the same operating area usually USES the same elevation.