{"id":20800,"date":"2020-05-29T23:53:17","date_gmt":"2020-05-29T23:53:17","guid":{"rendered":"https:\/\/www.lifeandnews.com\/articles\/?p=20800"},"modified":"2020-06-01T14:46:13","modified_gmt":"2020-06-01T14:46:13","slug":"when-dams-cause-more-problems-than-they-solve-removing-them-can-pay-off-for-people-and-nature","status":"publish","type":"post","link":"https:\/\/www.lifeandnews.com\/articles\/when-dams-cause-more-problems-than-they-solve-removing-them-can-pay-off-for-people-and-nature\/","title":{"rendered":"When dams cause more problems than they solve, removing them can pay off for people and nature"},"content":{"rendered":"

Jon Honea<\/a>, Emerson College<\/a><\/em><\/p>\n

Across the United States, dams generate hydroelectric power, store water for drinking and irrigation, control flooding and create recreational opportunities such as slack-water boating and waterskiing.<\/p>\n

But dams can also threaten public safety, especially if they are old or poorly maintained. On May 21, 2020, residents of Midland, Michigan were hastily evacuated when two aging hydropower dams on the Tittabawassee River failed, flooding the town<\/a>.<\/p>\n

I\u2019m an ecosystem scientist and have studied the ecology of salmon streams<\/a> in the Pacific Northwest, where dams and historical over-harvest have drastically reduced wild populations of these iconic fish. Now I\u2019m monitoring how river herring are responding to the removal of two derelict dams on the Shawsheen River in Andover, Massachusetts.<\/p>\n

There\u2019s growing support across the U.S. for removing old and degraded dams, for both ecological and safety reasons. Every case is unique and requires detailed analysis to assess whether a dam\u2019s costs outweigh its benefits. But when that case can be made, dam removals can produce exciting results.<\/p>\n

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Between 1850 and 2016, 63 dam failures with fatalities occurred across the U.S., killing an estimated 3,432 to 3,736 people.<\/span>
\nNational Performance of Dams Program, Stanford University<\/a>, CC BY-ND<\/a><\/span><\/figcaption><\/figure>\n

Pros and cons of dams<\/h2>\n

It\u2019s relatively easy to quantify the benefits that dams provide. They can be measured in kilowatt-hours of electricity generation, or acre-feet of water delivered to farms, or the value of property that the dams shield from floods.<\/p>\n

Some dam costs also are obvious, such as construction, operation and maintenance. They also include the value of flooded land behind the dam and payments to relocate people from those areas. Sometimes dam owners are required to build and operate fish hatcheries<\/a> to compensate when local species will lose habitat.<\/p>\n

Other costs aren\u2019t borne by dam owners or operators, and some have not historically been recognized. As a result, many were not factored into past decisions to dam free-flowing rivers.<\/p>\n

Research shows that dams impede transport of sediment to the oceans<\/a>, which worsens coastal erosion. They also release methane<\/a>, a potent greenhouse gas, as drowned vegetation beneath dam reservoirs decomposes.<\/p>\n

One of dams\u2019 greatest costs has been massive reductions in numbers<\/a> and diversity<\/a> of migratory fish that move up and down rivers, or between rivers and the ocean. Dams have driven some populations to extinction, such as the iconic Baiji, or Yangtze River dolphin<\/a>, and the once economically important Atlantic salmon<\/a> on most of the U.S. east coast.<\/p>\n

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Old dams under stress<\/h2>\n

As dams age, maintenance costs rise. The average age of U.S. dams is 56 years, and seven in 10 will be over 50 by 2025<\/a>. The American Society of Civil Engineers classifies 14% of the nation\u2019s 15,500 high hazard potential dams<\/a> \u2013 those whose failure would cause loss of human life and significant property destruction \u2013 as deficient in their maintenance status, requiring a total investment of US$45 billion to repair.<\/p>\n

Like the failed Michigan dams, which were built in 1924, older dams may pose growing risks. Downstream communities can grow beyond thresholds that determined the dams\u2019 original safety standards. And climate change is increasing the size and frequency of floods in many parts of the U.S.<\/p>\n

These factors converged in 2017, when intense rainfall stressed the Oroville Dam<\/a> in Northern California, the nation\u2019s tallest dam. Although the main dam held, two of its emergency spillways \u2013 structures designed to release excess water \u2013 failed, triggering evacuations of nearly 200,000 people.<\/p>\n