Development of a Real-Time Flood Prediction and Warning System for Underground Excavation Sites Based on Nomographs

In August 2022, a localized torrential downpour in Seoul highlighted the growing frequency of extreme rainfall events linked to climate change. Simultaneously, rapid urbanization has led to higher population densities and an increase in underground space development and excavation projects, such as the Yeongdong-daero complex transit center and the construction of the Greater Seoul Metropolitan Express Railway (GTX). This study examines the risks to evacuation routes at ‘underground excavation sites’ during heavy rainfall. Based on this analysis, a system for calculating evacuation buffer time and providing real-time flood forecasting and warnings were developed. A testbed was established in a basin susceptible to recurrent flooding, driven by seawater, external water, and internal water. The study modeled excavation sites with depths of less than 10 m, which were the areas currently excluded from intensive underground safety regulations. The flood risks along the evacuation routes were quantified using a depth-velocity product model. To stimulate real-time flood risks, a rainfall scenario was created by combining observed and predicted rainfall data from the weather radar. The real-time flood forecasting and warning system developed in this study, if implemented nationwide in flood-prone areas, could provide timely warnings to site managers and officials, enabling immediate evacuation based on the risk assessments of evacuation routes in different rainfall scenarios.