A cross-scale modeling framework for simulating typhoon-induced compound floods and assessing the emergency response in urban regions

Abstract

The cities within the Pearl River Delta (PRD), known as the Greater Bay Area (GBA), are flood-prone areas that faced frequent threats from typhoon-induced storm surges and rainfall in recent decades. To assess the potential consequences of a typical typhoon event, fine-scale simulations of inundation induced by both pluvial and fluvial flooding (known as compound flooding) are crucial for policymakers and concerned stakeholders to develop proper measures. In this study, we develop a cross-scale framework for modeling city inundation arising from typhoon-induced surges and torrential rainfall–runoff by coupling a three-dimensional ocean model (FVCOM) and a one-dimensional and two-dimensional coupling river analysis system (HEC-RAS). The ocean model is applied to capture the mesoscale behavior of surge and tide propagation from the deep sea to shallow offshore areas near the PRD. The river analysis system can simulate storm wave propagation along rivers, overtopping banks on floodplains and rainfall–runoff-induced flooding in urban regions at gradually refined scales. Second, the framework integrates GIS components (network analysis) with these hydraulic models. Through this framework, the urban emergency service coverage can be assessed under various potential flood scenarios during typhoon landfalls. Super Typhoon Mangkhut in 2018, the most devastating typhoon in the last decade in the PRD, is used as a case study in simulating and studying the flooding process. The simulated results show that in this typhoon event, pluvial and fluvial flooding play different roles in hindering the accessibility of emergency resources. Moreover, the interaction between pluvial and fluvial flooding significantly affects some urban regions.