between river and land. Specifically, periodic flooding replenishes the soil on the floodplain, provides nutrients for vegetation, and creates habitats for animals. In the coastal areas, flooding in tidal rivers can add saline water to the floodplain and regional groundwater due to the seawater and freshwater interactions (Yabusaki et al., 2020). Two-way coupling of land and river components in Earth System Models (ESMs) is necessary to accurately simulate the impacts of floodplain inundation on water and biogeochemical cycles. Simple macroscale inundation schemes have been coupled to global river routing models to simulate floodplain inundation dynamics (