New sediment continuum measurements in the Brda River (Poland): the results of the functioning of the 50‑year Koronowo dam

Purpose: As documented by multiple studies, the construction of artificial reservoirs influences fluvial processes. The hydrographic barrier causes a water regime change, and the effects are evident in the accumulation of sediment in the reservoir as well as the intensification of the erosion process below the dam due to the lack of sediments for transport in the river. Moreover, the use of lateral canals on the reservoirs causes additional transformations of the river system, excluding the river part below the dam from the natural system of the catchment area. This research aimed to determine the impact of the creation and functioning of the Koronowo Reservoir dam on the Brda River and its lateral canal on the continuum of sediment transport, with particular emphasis on suspended sediment. Methods: The research was based on analysing the available hydrological data and the measurements of suspended sediment concentration during the water flushing maintenance works into the Brda River channel. In addition, a set of morphometric indices obtained through dedicated terrain analysis were necessary to understand the area’s morphodynamics and sediment sources. The suspended sediment concentration (SSC), suspended sediment volume concentration (SVC), and Sauter mean diameter (SMD) data were measured by a LISST-25X, and spatial data were obtained through the System for Automated Geoscientific Analyses (SAGA GIS) software. Results and conclusion: The results were combined with the Connectivity Index evaluation as well as field surveys and made it possible to identify new sources of material supply to the Brda catchment below the dam, thus identifying a disturbance in the sediment transport continuum in the catchment area. Research is a critical element in sustainable sediment management in the catchment, using a controlled sediment flushing operation and identifying local new sources of sediment supply.