Assessment of climate change impacts through IDF curves: A case study of Surat Thani Province

Abstract

This study compares the Intensity-Duration-Frequency (IDF) curves derived from rainfall data at stations X.36 and X.260 during the period 2017-2024 with the standard IDF curves from the Engineering Institute of Thailand (EIT) published in 2005. The objective is to assess trends in rainfall intensity changes in Surat Thani Province. The 2024 IDF curves were developed using 15-minute interval rainfall data from telemetry stations of the Royal Irrigation Department, covering the period from 2017 to 2024. In contrast, the EIT IDF curves from 2005 were based on historical rainfall data from multiple stations across Thailand. The results indicate that the 2024 IDF values from stations X.36 and X.260 are consistently higher than those of the EIT 2005 standard across all return periods, with differences becoming more pronounced for more extended return periods. Additionally, the IDF values at station X.36 are generally higher than those at station X.260, highlighting spatial variability in rainfall intensity within the province. This increase in IDF values may be attributed to factors such as climate change, an increased frequency of extreme rainfall events, or differences in the datasets used for analysis. While the EIT 2005 IDF curves have been widely used as a standard for stormwater infrastructure design, this study suggests that rainfall intensities have increased over time, potentially affecting the effectiveness of existing drainage systems. Therefore, updating IDF standards to reflect current climatic conditions may be necessary to enhance urban flood resilience and improve infrastructure planning.