Flood Simulation Studies with Rainfall-Runoff-Inundation (RRI) Model, Over Yangon City, Myanmar

Flood risks are increasing due to climate change and human activities in river basins. Flooding is one of the most common disasters in Myanmar, as well as in many other countries. The floods occur during the southwest monsoon season, which is from May to October. Yangon City is at risk of flooding when heavy monsoon rainfall coincides with high tides. In this study, the Yangon area was used as a case study, and the Rainfall-Runoff-Inundation (RRI) model was applied. The RRI model is one of the models that has been applied in various river basins to estimate river discharges and flood inundation from rainfall data. The model is a two-dimensional model capable of simulating rainfall-runoff and flood inundation simultaneously. This study aimed to clarify the characteristics of the model's parameters, such as lateral saturated hydraulic conductivity ka and soil depth hd, for a flat river basin in Yangon. Eighty numerical simulations were conducted for four flood events in 2011, 2012, 2013, and 2014, with six soil depths hd and five different ka values in the Bago River. The discharge hydrographs with different ka and soil depths hd values for this river basin were compared. The results show that ka and soil depth hd values significantly differ between Myanmar and other countries due to the geological characteristics and climate zones of the countries.