This course aims to give a general overview of numerical modeling approaches to reproducing water-related natural hazards. Analytical solutions are outlined for validation/verification purposes. Theoretical aspects will be then applied to a series of test cases, in particular related to (i) tsunami generation, propagation, and interaction with water body boundaries, (ii) wind driven waves propagation and interaction with coastal and harbour structures, (iii) river flow and (iii) detailed simulation (i.e. CFD) of wave-structure interaction. At the end of the course the students will be able to design and perform numerical investigations in typical real cases within the frame of water-related hazard assessment studies.