Fractured-porous media and karst systems remain one of the most challenging geological media to investigate due to their high heterogeneity and scale-dependent flow and transport properties. Given their abundance they are of importance for various research fields such as hydrogeology, geothermal energy, CO₂ and nuclear waste repository management, as well as petroleum and mining engineering. Decades of research have explored a broad method spectrum including field experiments, laboratory-scale approaches, analytical techniques and numerical modeling. However, the multiscale nature of these systems requires to bridge micro- and macro-scale processes in order to accurately represent flow and (reactive) transport processes. In this session we therefore welcome contributions that focus on flow and (reactive) transport in karst systems and fractured-porous media. Topics include but are not restricted to: (1) Advances in field methods and laboratory techniques to characterize flow and transport from pore to field scales; (2) Numerical and analytical modelling approaches models for multiscale process understanding; (3) studies targeting the management and efficient use of geothermal, mineral and petroleum resources; and (4) studies targeting water resources management and environmental risk assessment.