How can soil erosion and rock slides be reduced near hills and farmland regions?

I know from experience that if you put plants in the hill, trees, bushes, flowers and whatnot. Most erosion and landslides are caused by water that has soaked through the soil causing it to become soft. But the plants soak up the water through the roots, making it harder to flood (Which means the ground has soaked up to much water so it floods)