Flood impacts and adaption for transportation

The adverse effect of climate change continues to expand, and the risks of flooding are increasing. The transport system is crucial for daily life and threatened heavily by floods. Despite advances in emergency management for transportation, we still lack an integrated framework to examine the impact of transport system under floods. In this study, we propose an integrated approach to quantitatively assess how floods impact the functioning of a highway system. The framework has three parts: (1) a simulation model to represent traffic, heterogeneous user demand, and route choice in a transportation network; (2) a flood simulator using future runoff scenarios generated from global climate models and the CaMa-Flood model; and (3) an impact analyzer, which superimposes the simulated floods on the traffic simulation system, and quantifies the flood impact on a transportation system. This framework is illustrated with different cases studies including the Chinese highway network, urban transportation networks in 40 cities in China and road traffic system in the Guangdong-Hong Kong-Macao Greater Bay Area. Because of climate change, adaptation strategies are critical for mitigating future flood damage. Our approach provides a quantitative assessment tool to evaluate the effectiveness of adaptation measures. The results show that for different global climate models, the associated flood damage to a transportation system is not linearly correlated with the forcing levels, or with future years and floods in different years have variable impacts on regional connectivity. These results have critical implications for transport sector policies and can be used to guide highway design and infrastructure protection. The approach can be extended to analyze other networks with spatial vulnerability, and it is an effective quantitative tool for reducing systemic disaster risk.