Tight coupling of groundwater and sewer models for compound flood modelling in coastal urban areas

Hydrological models often neglect the interplay of flooding mechanisms such as storm surge, rainfall, high tide, and groundwater emergence that may occur in coastal urban areas. Therefore, they could provide inadequate predictions. In this paper, we report on a study aimed at developing an algorithm to tightly couple groundwater and sewer models that could be applied to effectively evaluate grey and green infrastructure performance during compound flooding in coastal urban areas. The models developed in open-source programs such as MODFLOW and SWMM were coupled with a custom-built Python algorithm. The coupled models were calibrated and validated for a test site located in Long Island (NY, USA). Overall, tightly coupled MODFLOW and SWMM models can represent a substantial advancement in urban hydrological modelling, offering both immediate practical benefits for flood management and long-term strategic value for urban water infrastructure planning.