Comparative Assessment of the Influence of Gradient and Wind Factors on the Redistribution of Flow at a Bifurcation Point of a Channel

A comparative assessment of the effect of gradient and wind factors on the redistribution of river discharge between river branches on a daily time scale was conducted using the results of direct measurements near a bifurcation point of the Pregolya River (Kaliningrad Oblast, southeastern Baltic) into two branches. Field measurements of flow velocity in autumn (16 days in 2022 and 25 days in 2023) and data of bathymetric survey of the channel beds (illustrating the morphometric features of the channel) were used. The redistribution of flow in favor of one of the branches coincided well with the corresponding imbalance in water levels between the mouths of these branches, caused by the backwater effect of the wind field over the region. The analysis showed that the gradient factor (the difference in water levels between the bifurcation point of the Pregolya channel, as the source of the branches, and the mouths of the branches) dominates, while local wind plays a role during periods of regime transition. For the first time, a rare and previously undocumented hydrodynamic regime has been instrumentally recorded: the Deima branch, near its bifurcation point, flows backward for an extended period (up to four days). The results are significant for geoecological studies, particularly in the context of the retention of suspended matter and pollutants in the river’s estuary.