An assessment of the frequency of maximum rainfall events in Hai Phong and Nha Trang

Extreme heavy rain events often cause severe threat to people and their properties in high-populated, especially in coastal cities. These events can be analysed with using data observed during the least 30 years to asses how the climate change has impacted local environments in Hai Phong and Nha Trang. The extreme rainfall events is defined as high values exceeding the 95th percentile for each station. The results shows that the high rainfall (95th percentile) is 333.58mm a day in Hai Phong and 301.18mm a day in Nha Trang. The highest rainfall 342.6mm a day in Haiphong and 348.7mm a day in Nha Trang. The result from the Mann-Kendall tests show that there is a decrease in the rainfall in Hai Phong during the years 1978-2007 while the trend of the rainfall in Nha Trang during the year 1979-2008 is unapparent. In order to estimate the duration of repeat extreme high rainfall events and the frequent distribution, the method General Extreme Value Distribution has been used. The duration of daily maximum rainfall is in a range of 2-100 years. The daily maximum rainfall within 50 years can be 330.14 mm in Hai Phong and 323.98 mm in Nha Trang. The daily maximum rainfall within 100 years can be 366.23mm in Haiphong and 359.99mm in Nha Trang.