Investigating the Changes in the Groundwater Flow Regime During the Most Recent High Floods in Budapest

Abstract Groundwater and surface water have a strong relationship in riverside municipal areas, although obstructed by buildings with underground structures that reach the aquifer. In the study area of Lágymányos (Budapest, Hungary), the groundwater level is highly influenced by the Danube. This research investigates these exchange processes in the case of a flood, and their changes resulting from the construction of two riverside buildings. These buildings were built between the earlier floods in 2010 and 2013 and the recent floods in 2023 and 2024. The specific groundwater discharge was computed by frequently monitoring the groundwater levels. The results are compared to the water level of the Danube and result in loop rating curves. These are approached with ellipses to examine their estimation. If obstructed, the parameters of the ellipses change for the earlier and newer floods. The calculations were also investigated at wells with no underground structures nearby. Further investigations could lead to an easier quantifying of the specific groundwater discharge.