When the pores in sediment become filled with water, the cohesion among particles is destroyed, allowing them to slide past one another with relative ease. For example, when sand is slightly moist, it sticks together quite well. However, if enough water is added to fill the openings between the grains, the sand will ooze out in all directions.Thus, saturation reduces the internal resistance of materials, which are them easily set in motion by the force of gravity. When clay is wetted, it becomes very slick-another example of the “lubricating” effect of water. Water also adds considerable weight to a mass of material. The added weight in itself may be enough to cause the material to slide or flow downslope.