ABSTRACT: In this study a numerical algorithm is developed for simulation and visualization of rainfall overland flows on natural topography. The algorithm is constructed based on the diffusion model of water flow which is solved numerically using an adaptive tree grid finite volume method which is equipped with dynamic domain defining. The developed algorithm is tested to simulate and visualize rainfall overland flows on natural topography showing the advantages of the algorithm in terms of computational costs and the simulation times without losing much accuracy in the results.