When the forest trees are cut down, then the lesser number of trees put less water vapour into atmosphere through transpiration. Since, less
water vapour is put into the atmosphere, there is less rainfall in that area.
When there is less rainfall in an area, then less water percolates into the ground. Due to this, the groundwater level also gets lowered. The
shortage of surface water (in ponds, lakes, etc) and groundwater due to persistent low rainfall in an area can lead to droughts.
Deforestation also leads to a decrease in the water holding capacity of the soil. When trees are cut down there are no roots for absorbing rain
water. Thus, the movement of water from the soil surface injo the ground is reduced.
So, there are floods. Soil erosion caused by cutting of trees also contributes to floods. The eroded soil keeps on collecting river bed, decreasing its
depth. This leads to overflow when heavy rains occur.