Theoretical Characteristics and Applicability of the Effective Rainfall Index Based on Railway Rainfall Hazard Cases in Korea

Climate change has heightened both the frequency and severity of extreme rainfall events, consequently elevating the risk of rainfall-induced hazards affecting railway slopes and earthworks. Current railway operation control criteria in Korea are mainly based on hourly and continuous rainfall; however, these indices have limitations in representing the residual effects of antecedent rainfall because continuous rainfall is reset after a specified rainless period. In this study, the theoretical characteristics and applicability of effective rainfall as a supplementary index for managing railway rainfall hazards were examined. Effective rainfall was formulated using a single linear reservoir model, with the half-life interpreted as a characteristic timescale controlling rainfall-memory decay. Hourly rainfall, continuous rainfall, and effective rainfall with half-lives of 1.5, 6, and 24 h were compared for three railway rainfall hazard cases in Korea using hourly rainfall observations. The results showed that the 24-h effective rainfall retained antecedent rainfall contributions that were removed by the continuous rainfall reset rule and reached reference levels earlier or at similar times in both long- and short-duration rainfall cases. These findings indicate that effective rainfall can complement current railway rainfall indices by continuously accounting for antecedent rainfall effects at multiple timescales, although the operational thresholds require further calibration using domestic railway data.