They now serve little purpose, but submerged dams that stretch across rivers throughout the country are killing swimmers, boaters and others swept into the churning water they create.
Researchers say that since the 1950s, more than 400 people have died at 235 so-called low-head dams in 38 states. About half of those deaths occurred in the past 15 years as more people spend time on rivers.
The dams, typically built in the early 1900s, can look harmless, but once people fall into the roiling water, they can be trapped by a wave of water forcing them to the bottom. The dams no longer generate electricity, but many residents like them because they create a wide, smooth waterway that's an attractive backdrop for a revived downtown.