Influences of sea level rise to the once-in-many-year water level of inshore area of China

The sea level rise has great effects on the security of coastal projects. The definition of check water level has always played an important role in coastal constructions. Under the circumstance of sea level arising, as time passes, the security of high check water level will descend eventually. This paper demonstrates that the sea level of inshore area of China has a tendency of ascending in general drawn from monthly average sea level data of 25 stations, with an average rate of ascending of 1.24mm/a. In the condition of sea level arising, the change of return period corresponding to high check water level with time is also studied using the method of the Gumbel distribution law. For the 21 stations in which the sea level arises, the once-in-50-year water level will decay to once-in-15.4-year one after 50 years while the once-in-100-year water level will decay to once-in-30.5-year one on average.