Discovery of old river branches: Hydrodynamic analysis of the Orava River in Slovakia

The revitalization of historical river branches is essential for restoring ecological balance, improving biodiversity, and supporting sustainable water management. These old channels, often altered or disconnected due to urbanization and development, provide natural flood protection, water filtration, and critical habitat. Restoring them reconnects fragmented ecosystems and strengthens climate resilience. This study explores the identification and analysis of historical branches of the Orava River in Slovakia using hydrodynamic modeling combined with historical maps and GIS data. The methodology enables the reconstruction of past river patterns and the evaluation of flow dynamics under various discharge conditions. A detailed digital terrain model was generated from topographic and bathymetric data to support 2D flow simulations. Modeling results revealed preserved remnants of former river branches that begin to refill at a flow rate of 55 m³/s, significantly lower than the Q1 flood level. However, reactivation under average flow conditions would require technical modifications to reconnect inlet and outlet sections. This research highlights the effectiveness of combining historical and modern tools in river restoration planning and offers a replicable approach for identifying and evaluating the restoration potential of disconnected river systems.