Because when there are no plants to control the flow n speed of water, to hold soil ,to let water seep n get in to the soil,the overflow of water from rivers rushes all around and causes flood, on other hand when there are no plants, no roots to hold soil, no stems to stop soil from being flown away with speedy winds,so,no soil,no seepage, no water table, no transpiration ,no humidity and no rainfall, as all events are interlinked. that’s why it causes drought….This way deforestation one side is responsible for flood other side for drought..
.
