Management Strategies for Sediment Transport in Reservoirs: Case Study of the Sĺňava Reservoir

Reservoir storage capacity is a fundamental parameter for sustainable water infrastructure. Over time, progressive sedimentation reduces usable storage, intensified by climate-driven flow variations and limited flushing. This study evaluates sediment dynamics and management strategies for the shallow lowland Sĺňava Reservoir on the Váh River, Slovakia. The methodology integrates: (i) field sampling and optical granulometry to determine bed material grain-size distribution; (ii) 1D analytical formulations to establish threshold discharge for incipient sediment motion; and (iii) 2D morphodynamic modeling in HEC-RAS 2D to simulate spatial erosion and deposition patterns. Investigated scenarios included baseline natural evolution, maintenance dredging, proposed engineered sedimentation pits, and bank groins under operational flow series and extreme floods (Q100). Results demonstrate that backwater delta aggradation is concentrated in the narrow upstream inlet reach between critical bridge profiles. Implementing targeted sedimentation pits combined with localized maintenance dredging proved to be the most effective strategy, trapping coarse bedload while mitigating scour near bridge piers. Conversely, groins provide localized flow redirection but complicate mechanical sediment removal. These findings highlight the necessity of shifting from reactive dredging to proactive morphodynamic management in regulated lowland reservoirs.