Development of an integrated flood hazard assessment model for a complex river system: a case study of the Mun River Basin, Thailand

Flooding is the most frequent natural disasters in Thailand, resulting in the loss of life and damage. In this research, we develop an integrated hydrologic and hydraulic model of the Mun River Basin, Thailand, and employ it to predict flood hazard maps at 10-, 25-, 50-, and 100-year return periods. The 'goodness-of-fit' statistics for probability distributions of rainfall data are investigated to select the best-fit distribution, which is used to derive the design rainfall depths for the scenarios (10-, 25-, 50-, and 100-year return periods). The results highlight the diversity of probability distributions even in the basin scale. The model demonstrates satisfactory results, and the flood hazard maps reveal that the extent of flooding is greater on the left bank than the right, and that the flood depths vary mostly between 0 and 4 m. The results also demonstrate that approximately 60% of floodplain inundation is < 1 m, which is mostly observed at the upstream and central areas of the river. The extent of flooding downstream is not as large as the upstream, but generally deeper. Due to the flat topography, the duration of flooding is long, which could damage crop growth and yield, including cities in the flooded areas. This information is essential for the government and authorities to develop flood-control measures and flood management strategies. In this case, planning and regulation of the use of land, and levees to protect the exposed cities are recommended. The integrated model can be further developed for the design of flood mitigation measures and flood forecasting and warning systems. The approach and parameters (both initial and calibrated ranges) can be used to guide future model development and in other basins with similar catchment characteristics, particularly where gauge data are not available.