Removing a Dam
A river without a dam carries sediment downstream, creating fertile farmland along its banks. A dam, however, traps water and sediment behind it. Water released from a dam carries less sediment, so it moves faster and scours the channel below.
France's Loire River
After many decades, a dam's reservoir becomes choked with sediment and the dam itself needs extensive maintenance. Some governments today are choosing to remove dams instead. In the 1980s, critics persuaded the French government to remove three existing dams in the Loire River basin and to abandon plans for new dams. The government also installed new flood warning systems along the river.
By destroying Saint Etienne du Vigan Dam in 1998, France re-opened one of the best spawning grounds for Atlantic salmon, causing an explosion in salmon populations. Removing dams sometimes has drawbacks as well. Although the Vigan reservoir was relatively clean, some dams hold back sediments laced with toxic chemicals.