One of the ways that deforestation negatively affects the environment is mudslides. In a healthy forest, the ground is completely covered with vegetation. Roots of this vegetation hold the soil in place, even in heavy rainfall. When you log off an area forest and remove the undergrowth, the soil is now no longer trapped in place by multiple root systems. When heavy rain happens, the soil is picked up by the flowing rainwater and carried downhill. If there are a number of days in a row with heavy rains, the remaining soil will become more and more saturated and heavier and heavier. IF there is enough rain, a critical point will be reached and entire walls of mud will break loose and flow downhill.