Evaluation of engineering measures on the Danube based on numerical analysis

Abstract

Shallow water depths in the southern arm of a widely intact bifurcation zone in the Lower Danube lead to a detour for navigation of ∼110 km on the way to the Black Sea at low discharges. In this study, different conceptual hydraulic engineering measures have been assessed with the goal of increasing the water depths in the southern arm, thereby also considering a minimized impact on fish migration (in particular sturgeons). The effects of the different measures were analysed based on a 3D hydrodynamic numerical model (RSim-3D) and a sediment transport model (iSed). The results show that transverse structures in the northern arm, dredging operations in the southern arm as well as a spur dike at the bifurcation might not lead to the desired success. The most promising alternative considering water depths for navigation and fish migration might be a modification of the river course.