Safety Design of Sea Dike Crest Elevation in Tianjin

The rapid development of Tianjin Binhai New Area induces concentrated distribution of social and economic wealth in coastal region, which faces the increasing risk of storm surge. Therefore, a safety design criteria of sea dike plays an important role inpreventing loss of wealth, life and personal injury caused by storm surge disaster. Project grade and design protective criteria of sea dike were determined according to the socio-economic condition and national standard. The sea dikes on the coastline north of Dashentang and the coastline south of oil field flood wall were designed to meet the safety criteria of 100-year return period, and the sea dikes on the coastlines between Dashentang and oil field flood wall were designed to meet the safety criteria of 200-year return period. High tide level were calculated at different return periods using Extreme Type-I distribution, based on 57 years' observational data form Tanggu tide gauge station. Putian Experimental Station formulas were applied in the calculation of wave elements and wave run-up. Crest elevation of sea dike was the sum of design high tide level, wave run-up and the safety free-board. Results showed that the safety design crest elevations of sea dikes at 100-year return period were 6.815m, 6.573m and 5.698m at the directions of NE, E and SE respectively. The safety design of crest elevations of sea dikes at 200-year return period were 6.985m, 6.743m and 5.868m at the directions of NE, E and SE respectively.