Assessment of the jacking effect of high tide on compound flooding in a coastal city under sea level rise based on water tracer modeling

High tide is one of the main drivers of compound flooding in coastal cities. The capacity of the coastal urban drainage network is reduced due to the jacking effect of the high tide, which will be further amplified by future sea level rise (SLR). Although most studies have evaluated compound flooding in coastal cities under SLR, there is still a lack of studies analyzing the jacking effect of high tide. In this paper, the jacking effect of high tide under SLR on compound flooding is quantified based on the water tracer method using Haikou City as an example. The water tracer method tracks water flow paths by realizing the coupling of water flow and tracer. The future sea level of Haikou City in 2050 is predicted using the MGF model and the SLR projection results of IPCC AR6. An urban flood model coupled with the tracer method is constructed to simulate the compound flooding of coastal cities under baseline and SLR scenarios. The results show that the extent and depth of compound flooding increases under SLR and the high tide has a more pronounced jacking effect on the drainage network and flooding. More than 13% of the drainage network and more than 40% of the flooded inundation areas in the study area experience significant jacking effect as a result of the high tide under SLR, and more than 80% of the areas experience jacking effect for more than 4 h. In addition, the effectiveness of pumping stations and storage facilities in regulating the jacking effect of high tide levels is assessed. For reducing the jacking effect of SLR on the drainage network, pump stations are considerably more useful than storage facilities. This study provides a theoretical basis for understanding the jacking effect of high-tide level under SLR and formulating measures to regulate the jacking effect.