Evaluation of wet indices using standard precipitation index: A case study of Terengganu states

In line with the current climate conditions, the study of prolonged precipitation is imperative as it may predict the flood events in the future. In 2014, Terengganu is amongst the state in Peninsular Malaysia was affected by floods and it experienced three waves of floods during the monsoon seasons. In this research study, Standard Precipitation Index (SPI) is used to analyse the monthly precipitation data for two selected rain gauge stations in Terengganu over the period of forty-five years from 1970 to 2014. The objective of this study is to monitor the extreme wet conditions that eventually could cause the occurrence of floods. Comparisons were made using 3-month, 6-month, 24-month and 48-month time scales. SPI time series is calculated from precipitation index data for two rain-gauge stations in Terengganu. The shortest of time scales of SPI indicate the condition of moisture in short and medium terms, which is then used to estimate the seasonal precipitation. The longest time scales reveal patterns of long-term precipitation before the flood events. The result clearly shows that the annual trends of the wet events for longest periods are regularly experienced in wet conditions compare to drought conditions and predicted to have a higher probability of flood disaster. SK Kuala Telemong station has recorded the highest SPI values for the wet event in the entire periods, which the shortest time scales is 3.43 and longest term of time scales closer to three (2.90) in this analysis.