<p>Understanding groundwater/surface-water connectivity fluxes in complex floodplains is crucial for hydraulic characterization and hydrological monitoring, particularly in flood-prone areas. Capturing variations in hydrological fluxes requires robust techniques that integrate spatial and temporal changes that are often missed by traditional methods. This study used a combined cross-correlation and flood rating curve approach to investigate groundwater/surface-water interactions in the Szentendre Island floodplain, representing a part of the Surány aquifer along the Danube River in Hungary. The results revealed that as the distance from the river increased, the slope of the flood rating curve decreased, and the hysteresis widths increased. Cross-correlation analysis showed correlation coefficients of 0.79–0.94 and time lags ranging from less than a day to 6&#xa0;days. These findings highlight a strong hydraulic connection between the river and aquifer, linking flooding to well water levels. These findings were consistent with prior understanding of the aquifer system, while providing deeper insights into hydrological processes. Further modelling is recommended to support water management in the area.</p>