CFD analysis of environmentally friendly wave mitigation measures in river waterways

Abstract

AbstractThe impacts of navigation on the hydromorphological and ecological conditions of rivers are manifold. Most of the relevant effects can be linked to ship‐induced waves, which temporarily alter the prevailing flow conditions. The impacts of waves are usually the highest in the shallower (littoral) zones, where the whole water column is affected by the increased flow velocities. The mitigation of these effects is desired to improve ecological conditions as well as prevent bank erosion processes. In this study, a numerical modeling‐based methodology is presented for the quantitative evaluation of environmentally friendly wave mitigation measures (inspired by already existing examples). The hydrodynamic effects of a timber piling‐type and gravel bar‐type breakwater is analyzed via the modeling framework through a case study in a Hungarian section of the Danube River. In addition, an ecohydraulic case study is presented for the predictive drift risk evaluation of juvenile fish (common nase). The prevailing flow velocities in the near‐bank area were in the limits of the swimming capabilities of the nase, showing the relevance of the impact and the need for its mitigation. The statistical evaluation of the hydrodynamic and ecohydraulic results showed the beneficial effects of the measures in a well‐comparable manner. Additional effects and the current limitations of the methodology are discussed.