A Study on the Method of Calculating Rainfall Thresholds Based on a Multimethod Approach to Provide Heavy Rain Disaster Impact Information

Various disasters have recently occurred in Korea because of weather changes caused by climate change, and the scale of the damage is also increasing. In terms of the weather phenomena and their socioeconomic impacts, weather-related disasters cause the most damage. Therefore, this study suggests a method of calculating rainfall thresholds to predict the impact of heavy rains. To calculate rainfall thresholds on the basis of a multimethod approach, this study divided Korea into a 1 km × 1 km grid and further split it into four categories: standard watershed, urban, river, and inundation trace maps. This study verified the results of the rainfall thresholds in the standard basin and city center by referring to the relevant data on the rainy season in summer 2020 and the Typhoon Haishen in September. Verification results showed that the flooding that occurred in the grid actually caused the urban flooding in Busan in July 2020. Moreover, the calculation on the grid that caused flooding in Gangneung, which was hit by Typhoon Haishen in September, reflected the actual damage. When used in impact forecasting, the proposed method of calculating rainfall thresholds and predicting rainfall information is expected to be able to provide data on the impact of heavy rains and facilitate rainfall forecasting.