In the early years of this nation and state, settlers built small dams on rivers and streams to capture waterpower for mills, enable navigation and assure a water supply. In the middle part of the last century even more were built as government agencies tried to bring waterways under control.
Today, thousands of those dams remain although new power sources and transportation methods, among other societal changes, have made most of them obsolete. Worse, almost all of them present a threat to humans and the aquatic environment.
In Kentucky alone, there are probably more than 1,000 of what are called low head dams — structures spanning a waterway that range in height from as little as one foot to about 15 feet.
“In a lot of cases they’re not being used at all, nobody even knows who owns them, they’re just sitting there crumbling and they’re just a hazard” said Ward Wilson, a former executive director of the Kentucky Waterways Alliance and now a board member.
Like many historic structures, they can be scenic. There’s still water, like a pond, above the dam and, below, spillways that look like horizontal waterfalls. But, unlike aging courthouses and elegant mansions, low head dams disrupt aquatic species and degrade our environment. And they kill people.
“It doesn’t look like much, it doesn’t look like some raging rapid, but the way the water flows, it’s really hard to swim out of,” explained Wilson. “People are out there wading and they get caught and they die.”
That dangerous aquatic vortex is variously called a boil, backwash, danger zone or a drowning zone.
A National Weather Service illustration dispassionately describes what it designates the “drowning zone” as “area of river in which only prompt, qualified rescue is likely to save a victim.”
And, just as there is no count of the number of dams themselves, there is no official database for dam-related deaths, either nationally or in Kentucky.
In Kentucky, there have been in the neighborhood of 40 fatalities documented in recent decades as kayakers, canoeists, tubers, swimmers and waders were sucked into their drowning zones. But Mike Hardin, assistant director of fisheries at the Kentucky Department of Fish and Wildlife Resources, says the death toll is much higher. “When you look up the history of some of these old dams … you will inevitably come across some old news story of somebody drowning. It is not new,” he said. As for the true total over the lifespan of the dams, he said, “I’d hate to think of what that number is.”
Water quality declines
Human deaths at low head dams are tragic and newsworthy. Less likely to capture headlines is the profound toll the dams take on aquatic species.
“The rivers have a lot of functions and processes, such as moving sediment and gravel,” Hardin explained. “When the river flows it keeps those things clean swept, it keeps the water cool, it provides more complex habitat so that results in healthier fisheries, more diverse and rich species.”
But when rivers are interrupted by dams that all breaks down. “The long and short of it is, you’re basically creating a kind of semi-pond,” explained Lee Andrews, the field office supervisor in Kentucky for the U.S. Fish and Wildlife service. “These structures that seem like pretty small, localized, man-made creations really have some wide-ranging effects.”
When water slows down or stands still, oxygen levels drop, the temperature rises and the sediment the water is carrying falls to the bottom, burying the gravel and stones on the stream floor, and the species that live there — invertebrates like mussels and crayfish — in mud.
In the loop that nature creates, declining water quality destroys mussels and a declining mussel population reduces water quality. While mussels are small, Andrews said, they are nonstop water purifiers. “That mussel is out there 24 hours a day, seven days a week, inhaling that water and filtering constantly. The more of them you have the cleaner your water is going to be.”
Dirty water kills mussels and the fewer mussels, the dirtier the water.
And there are many fewer. Of the 103 species of mussels native to Kentucky, 20 are no longer found here and another 36 are considered endangered or threatened.
Damming streams also damages fish populations. Surveys have found the population of smallmouth bass “was 1,500% higher in free flowing water than it was in the impounded water,” Hardin said.
In addition to higher temperatures and reduced food supply, dams also take a toll by isolating populations of the same species above and below the impoundment, which decreases the genetic diversity “that makes that species a little more resilient,” Andrews said.
Plus, more species find homes in the stream when dams are removed. This summer, a year after a dam was removed on the Barren River, Andrews said, “we started finding some fairly rare fish were showing up on some of those habitats that were created.”
Beyond the individual streams and the species that occupy them, the entire watershed benefits, said Rich Cogen, president of the Ohio River Foundation. Removing dams improves water quality in streams flowing into the Ohio, which American Rivers recently designated an endangered river, and “since the water quality is better in those rivers then the water quality is improved in the Ohio River,” Cogen said.
Removal is costly and complicated but cheaper than replacing a dam
The benefits are many but the number of low head dams removed is few, perhaps seven to 10 in total in Kentucky in the last several years. There are a lot of reasons for the slow pace. It can be costly, although never as expensive as replacing a failing or damaged dam. Sometimes it’s not even clear who owns a dam and obtaining all the permits — federal, state and sometimes local — required to remove a dam, can be a long and complicated process.
Cogen, who has been involved in several dam removals in Kentucky and Ohio, said there can also be concerns about water supply. “Land owners get nervous but really only people very close to the dam are going to see significant change,” he said. When a dam was removed near Owingsville a couple of years ago, a farmer upstream was worried about losing his water supply but the change “was imperceptible.”
And, people don’t like change.
When a dam has been in place for decades or centuries, the people who live nearby have a store of memories built around the way it has always been.
Dam 6 on the Green River failed in 2017, becoming a hazard, and had to be removed, Andrews said, but it was a sad leave-taking. “We heard stories like ‘my grandpa taught me how to fish right here,’ ‘me and my girlfriend, now my wife of 55 years, used to come down here and picnic.’”
Andrews and others said that removing dams typically provides more opportunities, and safer ones, for recreation. Often, much of the debris from the dam is broken up and used to stabilize the banks, and the project includes creating a small park and new access to the water. Canoeists and kayakers no longer have to portage around the dams and people can play and swim safely in the free flowing water.
Andrews’ message is simple: “If you know of one of these places don’t be afraid to allow somebody to take it out.”
The benefits, he said, “spread all across society.”
A healthier environment means more species thrive and fewer have to be listed as endangered which prompts regulatory intervention. But Andrews said that his agency doesn’t want to spend its time creating and enforcing regulations, it wants to save species. “We just want to have better habitat and more critters moving around out there for people to enjoy.”
Bass like free flowing water
The Kentucky Department of Fish and Wildlife Resources surveyed sport fisheries to compare free flow vs. impounded flow in the Barren and Green rivers and found notable differences based on habitat.
Barren River sport fishery
Dominant Species:
- The free flow section of the fishery is dominated by smallmouth bass, spotted bass and rock bass. These species reach quality and trophy sizes.
- The impounded sections fishery is dominated by largemouth bass, spotted bass and bluegill. These species on average do not reach the quality sizes that anglers prefer.
Abundance of species:
- Black bass catch rates averaged 106% higher in free flow sections.
- Smallmouth bass, the more desirable stream black bass, catch rate averages 600% higher in the free flow sections.
- Rock bass catch rates average 3,731% higher in the free flow sections.
- Bluegill are the only sport fish species that is more prevalent in the impounded sections.
- Overall, sport fish catch rates of all species combined was 51% higher in the free flow sections than the impounded sections.
Green River sport fishery
Dominant species:
- Upstream of Mammoth Cave National Park the free flow fishery is dominated by smallmouth bass, rock bass and channel catfish. These species reach quality and trophy sizes.
- Pool 5 (impounded) is dominated by spotted bass, largemouth bass and bluegill. These species on average do not reach the quality sizes that anglers preferof Black bass catch rates averaged 69% higher in the free flow sections.
Abundance of species:
- Smallmouth bass, the more desirable stream black bass, catch rates average 155% higher in the free flow sections.
- Rock bass catch rates average 2,600% higher in the free flow sections.
- Bluegill are the only sport fish species that is more prevalent in the impounded sections.
- Overall sport fish catch rates of all species combined was 114% higher in the free flow sections than the impounded sections.
