Current elevation of Tianjin tidal zone and the urban safety of Binhai New Area, China.

Based on 6 leveling sections across the tidal zone of Tianjin Binhai New Area, the height and slop of tidal zone were measured and calculated. The elevation of the interface between anthropogenic coastline (seawall, coastal road and so on) and the natural tidal zone is from +0.22m~+0.73m (1956Huanghai Elevation System). The slop results of the tidal zone show that the average slop of Tianjin tidal zone is 1.25‰, and the average slop of tidal zone on the south Haihe River is 1.09‰ and of the north is 1.33‰. The slop increases from Chengtougu(1.21‰) to Dashentang(1.58‰) section. Based on tide observation data, the width of tidal zone were obtained and the results show that the widest one is Yongdingxinhe tidal zone, 1730~1810m, and the narrowest one is Dashentang tidal zone, 1900~1160m. The slop of the tidal zone increases and the width of the tidal zone become narrow from 1980s to now. Furthermore, the elevation of the interface between anthropogenic coastline and the natural tidal zone were lower than mean high water level, which reveals a situation that the artificial constructions are influenced by sea water directly now. This paper presents that the coastal embankment has really become the only barrier protecting the urban safety, so further heightening, strengthening coastal defense facility, upgrading prevention level is necessary.