Development of rainfall intensity-duration-frequency curves for the Fiji Islands: integrating TRMM-3B42 and measured gauge data with future projections

ABSTRACTThis paper explores the utilisation of gauge rainfall and satellite-based precipitation product (SPP)-TRMM3B42, to develop IDF curves for the Fiji Islands. The study compares the application of remote sensing data against rain gauge (RG) data for two main stations, Nadi and Nausori (1991 to 2020). The accuracy of SPPs is evaluated through statistical analysis, employing continuous and categorical evaluation indices. The results indicate that TRMM3B42 tends to overestimate light precipitation and underestimate heavy rainfall in low elevations when compared to rain gauge data. Rainfall intensities derived from satellite data exhibit relative changes within ± 10%. This study also performs future projections. Two greenhouse emission scenarios, Shared Socioeconomic Pathways (SSP) 2–4.5 and 5–8.5, are employed for IDF curve projection. The analysis reveals that changes in IDF curves are more pronounced for short-duration rainfall as compared to high-duration rainfall. Additionally, higher emission scenarios demonstrate greater changes compared to lower scenarios. These findings emphasise the importance of accounting for climate change and future projections in designing urban infrastructure, particularly considering potential urban expansion and human settlements. This study helps in solving design problems associated with urban runoff control and disposal where knowing the rainfall intensities of different return periods with different durations is vital.