dam

And so the idea of restoring Hetch Hetchy died a death that seemed every bit as irreversible as the one John Muir and the Sierra Club had suffered in 1913, when a snow-job by "progressive" San Francisco politicians fooled Congress into believing that damming Hetch Hetchy was the way to bring the greatest good to the greatest number of people--despite the fact that at least three other alternative sites had been studied in the Sierra Nevada.

Elevation data collected at 80 sites in the canyon--primarily at pools just upstream of major rapids--suggest that the debris damming those pools is on average 26 centimeters higher now than it was when those same spots were surveyed in 1923.

Similarly, fisheries that are sustained by flooding undergo an estimated 30-70% decrease in output with resulting losses in food and income as a result of damming, according to the Food and Agriculture Organization of the United Nations.

Bureau of Reclamation, gave a speech lambasting environmentalists for their opposition to damming up the Grand Canyon national park.

Damming and diverting rivers damage the trust by preventing the natural flow of sand to the beaches.