What are the 5 major disadvantages …

The disadvantages of building large dams are:

• Damming of rivers and regulating their flow result in excessive sedimentation at the bottom of the reservoir. This may hamper aquatic life and their migration to other water bodies.
• Building of dams result in the submergence of land and vegetation. This results in the decomposition of vegetation.
• Construction of large dams results in the displacement of villagers and communities. The villagers have to give up their lands and their means of livelihood.
• Large forest areas are also submerged because of the building of dams. This threatens our biodiversity.
• Dams which were initially built to control floods are now causing floods because of sedimentation. In case of excessive rainfall, the release of water from dams often floods the area, causing damage to lives and property.