Modelling of Short Duration Rainfall IDF Equation for Sagaing Region, Myanmar

Abstract

Changes in the hydrologic cycle due to increase in greenhouse gases cause variations in intensity, duration, and frequency of precipitation events. This study regards the development of the IDF curves for Sagaing rainfall station in Myanmar. Sagaing is a rapidly growing city in terms of population and intense urban growth, due to which ponds and lakes are continuously encroached by human activities. Daily maximum rainfall data for the year 1989 to 2018 (30 years) was collected from Department of Meteorology and Hydrology (DMH) and the empirical reduction formula was used to estimate the short duration rainfall using different probability distributions. Gumbel’s Extreme Value Distribution and Log Pearson Type III Distribution are used to forecast rainfall for various return periods. Hourly rainfall were converted for shorter duration. Then, rainfall intensity for these shorter durations were determined using empirical formula and, IDF curves for studied stations were developed. Moreover, empirical equations related with rainfall intensity and duration were also developed using least square method. The IDF curve was then plotted for short duration rainfall of 15, 30, 60, 120, 180        , 240, 300, 360, 420, 480, 540, 600, 660 and 720 minutes for a return period of 5, 10, 25, 50 and 100 years. The result of IDF curves and empirical equations can be used for planning and designing hydraulic structures and water resources related projects. The correlation value R for various return period has -1. It is seen in the study that equation i =x*t_d^-y with parameter, x varying between 500 and 900 whereas the parameter y remains a constant of 0.67 is the best IDF empirical formula.