On the Columbia River for example, salmon heading upstream to spawn are stopped by the man made dam built in the middle of the river. Socially, people are impacted by, resettlement due to the construction of the dam. It is estimated that 30 million people have been ousted by dams. They say that it can be a death sentence to a community. The dam itself can also be a tourist attraction.
Hydroelectric power is so attractive because it is cheap.
The consumer price is about 3 cents per kilowatt hour. The low cost to the consumer reflects the relatively low operating costs of the hydroelectric facilities. Most of the cost of hydroelectric plants are the costs involved in building the dams. Operating costs are about .6 cents per kilowatt hour, where coal plants average around 2.2 cents per kilowatt hour, which includes the cost of mining, transport, and distribution. Dams frequently cost more and take longer to build than anticipated, sometimes to a great degree.