Extreme values and rising tendencies of sea levels along Vietnam coast

Abstract

A review of the investigations on the sea level changes in South-china sea is presented. The full set of year1y sea level data at 25 tide gauges along Vietnam coast is used for extreme analysis and trend analysis. Based on the level data collection up to year 2007 the empirical extreme analysis yields new estimates of the design values of sea level with different rare frequencies.

The results of extreme analysis are compared with the theoretical extreme heights of tide obtained by predicting hourly tide heights in a 20-year period. For stations with 11 harmonic constants of main tidal constituents the theoretical astronomical extreme tide levels were calculated by the Peresipkin iteration method. The comparison showed a good agreement between two methods. The analysis also showed that the tidal extremes and design level values of 20-year return period are of the same range. The level values of longer return period are affected mainly by floods and surges at a decreasingly extent.

The rate of yearly changes of sea level due to global warming and other effects is evaluated to be about 1 mm per year.