Mass movement in Siwalik Siwalik is a highland region between the Mahabharat and Chure mountain ranges in Nepal. The region has huge deposits of calcium carbonate. Common types of mass movement in the siwalik are gully erosion, slumping, toppling and rock fall.
 a. Rock fall: Rock fall is defined as the abrupt movement of rocks that become detached from steep slopes of cliffs. Movement occur by free fall or a series of a leaps and bounds.

 b. Mud flow when a rapidly moving stream of water mixes with sufficient amount of debris, it forms a pasty mass. The movement of such mass downward the slope is called mudflow. It contains about 50% of sand, slit, and clay sized particles. Many mudflows start after heavy rains in mountain valleys. They have a long, narrows track and spread out on reaching the lower ground. 

c. toppling A topple is a block of rock that rotates on a hinge and then separates from the main mass falling on the slope. It involves considerable volume of rock. If we weight vector lies outside the base of the block, toppling will occur. the danger of toppling increases slopes as well as discontinuity angle.

 d. gully erosion it is the removable of soil from rivulets, which are formed due to sufficient accumulation of overland flow on the slope ground. If the turbulence in the flow through the rivulets is strong enough, it may dislodge soil particles from bed and banks leading gully erosion.

 e. Slumping The frequency of sliding increases considerably in rainy season as the soft rock saturated with the rain water acts like semi-fluid. The rain water penetrates the rocks along the fractures and joints, thus exerting enormous pressure and causes high slumps.

 Image: Wikipedia, Distribution of the Siwalik sediments