Abstract
The 2011 flood over the Chao Phraya River Basin was induced by an amount of the rainfall that accounts for about 1.4 times greater than normal years one. Frequencies of rainfall and flood inundation in 2011 were analyzed in present and future condition using AGCM and RRI. The results showed the six month rainfall amounts those were the most correlated with maximum inundation volumes were 994mm, 1078mm in average with 195mm, 238mm standard deviation for present and future condition respectively. Also the results showed inundation volumes were 42mm, 60mm in average with 43mm and 57mm standard deviation for present and future condition respectively. According to Gumbel distribution, the return period of 2011 six month rainfall amount decreased from 24 years to 9 years and according to exponential distribution, the return period of 2011 inundation volume decreased from 29 years to 12 years for present and future condition respectively.
