Abstarct: Avalanche is a mass of snow, which suddenly and quickly starts to fall down a mountainside on the slope because of the gravity or external forces such as explosion. This natural phenomenon often occurs in mountain areas, especially in winter, and causes a lot of damage every year in Iran and in the world to visitors or those who live in the cold mountainous areas. Therefore, recognizing the avalanche flowing and movements can provide solutions to reduce its damage. In this thesis, avalanche has been simulated as a powder-snow avalanche (cloud consisting of two fluids with different properties) and avalanche consisting of a dense core of snow that is covered by powder snow (dense- powder avalanche) by using Smoothed Particle Hydrodynamics (SPH) method and by using the ABAQUS® software. SPH is a meshless Lagrangian method, which presents the fluid through a set of particles instead of mesh in which each particle has its own place, velocity and mass. In this thesis, avalanche is simulated as a mass of snow, which starts to move on the slope because of the gravity force and only applied frictional force to the avalanche. Finally, effect of the obstacles on the progression and velocity of avalanche has been investigated. At last, the obstacle that causes the greatest reduction in speed and progression of avalanche has been chosen. As it is seen, using obstacle in the separated form reduces the velocity and progression length of the avalanche. However the space between obstacles must be chosen in a way to have the biggest influence. Sometimes due to the existence of water at the end of the slope, when avalanche impacts to the water, it makes a wave and it causes overflowing of water from a dam, which can be a serious threat for towns, roads and infrastructures in downstream. In this thesis at first, the motion of avalanche on slope, created wave by impact of avalanche with water and velocity and height of water at the moment of crossing the dam have been simulated. Then according to the obtained results, global obstacle and obstacle in the separated form has been used in this model. In each case avalanche velocity at the moment of impaction, wave’s height, height and velocity of water at the moment of crossing the dam are compared with no obstacle case.