The Hydrologic Engineering Center River Analysis System (HEC-RAS) software package developed by the U.S. The Army Corps of Engineers is a widely used software package designed mainly for modeling steady and unsteady water flow in rivers. Although the software includes tools for implementing basic control elements, HEC-RAS users often require additional unique functions including integration with other software. This is made possible by means of the HEC-RAS Controller, an application programming interface (API) that allows manual interaction with HEC-RAS to enable automated control through user-defined code directly from other programming environments. The main goal of this study was to design a universal software architecture for linking HEC-RAS with Visual Basic using the API, which enables users to enter the unsteady flow boundary condition directly as the demand power output if the river system under analysis includes a hydropower plant. The effectiveness of the proposed approach and its applicability to real-world operational management environments were demonstrated through a case study of the Gabčíkovo hydropower plant on the Danube River in Slovakia. The integration of the HEC-RAS with Visual Basic enabled the simulation of the Danube River's water-level regime within a reasonable time and with adequate accuracy, allowing for the analysis of the impact of daily flow regulation on navigation conditions downstream of the hydropower plant.

During heavy rainfalls, overflowing sewage water flows from the Combined Sewer Overflow (CSO) chambers and pollutes the Trnávka River in Trnava, Slovakia. This paper aims to propose water retention measures for the Trnávka River as a remediation technique for CSO-affected watercourses, which can contribute to the ‘flushing’ of the riverbed. During heavy rainfalls, the Trnávka River is polluted by solid, non-soluble materials, which produce unpleasant odors and are the subject of numerous complaints by citizens, particularly during low water levels. Three inflatable rubber weirs were designed, and their design was verified using a 1D numerical model of the Trnávka River. The simulations of the proposed measures performed in the HEC-RAS 5.0 software excluded the adverse effect of the backwater on the functioning of the CSO chambers in the city of Trnava during normal flow rates and confirmed that, even after installation of the weirs, the transition of the flood wave will pass in the riverbed, not causing the flooding of the adjacent area. The chemical–physical study of the Trnávka River confirmed our assumption that higher flow rates, which can be secured by the regulation of the proposed weirs, can contribute to the purity of the watercourse in the city of Trnava.

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.

Reservoir storage capacity is a fundamental parameter for design and operation. Over time, sedimentation—driven by factors such as geology, hydrology, and flow velocities—reduces usable volume, often significantly. In the context of climate change, opportunities for natural sediment flushing have become increasingly rare, while extensive dredging is often economically unsustainable. Moreover, sedimentation is closely linked to erosion processes that may endanger bank stability or compromise bridge piers. This study presents a case analysis of the Sĺňava Reservoir on the Váh River in Slovakia, a typical shallow, lowland reservoir within the Váh Cascade hydropower system. In recent years, sediment-related issues have intensified due to declining flow rates and limited options for reusing excavated material. To address these challenges, several mitigation measures were proposed, including riverbed dredging, groins, and sedimentation pits. These measures were evaluated using a two-dimensional numerical model developed in HEC-RAS (Hydrologic Engineering Center's River Analysis System) to simulate sediment transport and morphological changes. The results indicate that the most effective approach combines targeted dredging with the implementation of sedimentation pits. Additionally, the findings highlight the importance of monitoring erosion processes near bridge piers to ensure long-term structural stability.