Development of Rainfall Forecasts Merging Method for Flood Forecasting Lead Time

Radar rainfall has been used as input data for short-term rainfall forecasting because it provides rainfall data with high spatial and temporal resolution. In 2019, the Korea Institute of Civil Engineering and Building Technology (KICT) developed a flash flood forecasting system using short-term rainfall forecasting that can provide real-time flash flood information with a one-hour lead time. The lead time of the system was set to one hour because the system operator considered it to be the minimum evacuation time. However, the accuracy of rainfall forecasting decreased significantly after one hour. In this study, a rainfall forecast merging method was developed to increase the lead time from one hours to three hours. Short-term rainfall forecasts produced by the Han River Flood Control Office (HRFCO) and numerical weather prediction (NWP) produced by the Korea Meteorological Administration (KMA) were used in the merging method. As a result, the accuracy of rainfall forecasting was improved to up to a three-hour lead time using the merging method.