Designing factorial experiments to investigate the impact of land subsidence on flood inundation in coastal areas during storm surges

The exacerbation of flood risks in coastal areas due to land subsidence necessitates a comprehensive understanding of the associated dynamics. In this study, the research employed a high-resolution and well-validated hydrodynamic model (MIKE 21) to predict coastal inundation in Zhuhai, Guangdong province, considering the combined influence of land subsidence and storm surge. To quantify the individual, main, and interaction effects of land subsidence and storm surge on coastal inundation, the study devised a factorial experiment. Our findings reveal the significant land subsidence in Zhuhai, primarily concentrated in a strip distribution spanning from northeast Pingsha town to southwest Baijiao town. Moreover, the reserch observed a spatial magnification effect of land subsidence on flood inundation. The interaction effect of land subsidence and storm surge intensifies the inland propagation of coastal floods, particularly on both sides of the Jitimen and Niwanmen channels. Furthermore, we found that the nearshore cropland and aquaculture areas exhibit greater sensitivity to land subsidence compared to urban inland areas. Notably, the combined effect of land subsidence and storm surge synergistically enhances flood inundation, thereby amplifying the individual effects of both factors. In the scenario of 100 years of land subsidence in Zhuhai, the main effect of land subsidence outweighs that of storm surge by a factor of approximately 1.11 to 29.49, underscoring the dominant role of land subsidence in coastal inundation. Consequently, accurate predictions of future coastal inundation resulting from storm surges must incorporate the consideration of land subsidence.