Dams and dam safety were front and center this week as a hundred thousand people were evacuated in California because of structural damage at the country’s tallest dam. The Oroville dam helps provide drinking water and hydroelectric power to millions of Californians. But 75 percent of Pennsylvania’s 3,000 dams are so-called “low-head dams” and don’t provide drinking water or create reservoirs for flood control. So in recent years, Pennsylvania has been making a big push to remove them with the help of conservation organizations like American Rivers. Recently, we caught up the group’s Lisa Hollingsworth-Segedy near a dam removal site on the Little Sewickley Creek near Pittsburgh to talk about why they’ve championed the issue.

LISTEN: Inside PA’s Big Push to Remove Old Dams

The Allegheny Front: In 2016, Pennsylvania actually led the nation in dam removals, removing 10 dams last year. That’s the 14th year in a row we’ve been first. So why so many here in Pennsylvania?

Lisa Hollingsworth-Segedy: We got an early start on dam removals in Pennsylvania because we had some really forward-thinking leadership at the state. Pennsylvania Fish and Boat Commission and the Department of Environmental Protection’s [division of] dam safety really led the way in terms of dam removals. American Rivers put people on the ground right around the year 2000 and started looking at dam removal for the ecosystem benefits and community benefits it could provide. The people in Pennsylvania’s regulatory agencies that we work with recognized early on that dam removal had some short-term impacts, but the long-term benefits outweighed those short-term impacts. As long as we work surgically and remove those dams carefully — and not let too much sediment or water go too quickly — we find it doesn’t have any bigger impacts.

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American Rivers’ Lisa Hollingsworth-Segedy shows how the dam removal on Little Sewickley Creek has changed the landscape. Photo: Kara Holsopple

AF: So what are some of the benefits of dam removal?

LHS: Well, using this stream as an example, the Western Pennsylvania Conservancy had five years of surveying data, and they found that there were, like, 32 species of fish below this dam and only 7 species above the dam. So what was happening was that fish we’re trying to swim up from the Ohio River and they could only get as far as the dam. So by removing the dam, the fish have access to almost the entire watershed here. It reconnected more than 17 miles of habitat, and that’s important because fish move upstream to smaller waters to reproduce. In addition, dams also impact oxygen levels in streams; they actually make it lower. You get this sort of bathtub effect, where you get water that’s slow behind the dam. It isn’t circulating and it warms up, causing the oxygen to dissolve. That makes it more attractive for invasive species. And then another reason for removing dams is the community benefits. You don’t have to worry about children falling in and drowning. There actually was a drowning here in the 1970s. Low-head dams kind of look like waterfalls or play features, but if you get caught in the hydraulic that’s below it, it’s almost impossible to escape. I think Pennsylvania is either number one or two in terms of dam-related drownings each year.

AF: So tell us about some of the dams that were removed in 2016?

LHS: There were two that I was directly involved with of the 10 on the list. One of them was on Pennsylvania State Game Lands. And it was the first of four dams that are coming out on Dunbar Creek, which is a really popular trout fishing area in Fayette County. Around 1900, the Connellsville Coke Company built this series of four dams, but they didn’t last very long; they all breached in a storm about 18 months after they were finished. So they were just left on the landscape. But fish need certain water flow requirements in order to be able to move. And when you have a small opening in a wide dam, it creates kind of a fire hose effect. A three-foot-tall dam can be just as damaging as a 25-foot-tall dam in terms of the impact to the community and the river.

Map: Pennsylvania Has Become a Leader in Dam Removals

Map courtesy American Rivers

AF: And improving trout streams has some big economic benefits, right?

LHS: The State of Pennsylvania makes millions of dollars every year on people buying fishing licenses, buying bait, buying lunch, maybe they spend the night. So anything we can do to connect the community to their river will add to that value.

AF: We’ve recently reported on how Pennsylvania is likely to get more rain in the coming decades due to climate change. So how can dam removals help mitigate the risks of flooding?

LHS: Well, I’ll use an example from one of the projects that we completed at the Harmony Junction dam on Connoquenessing Creek, just upstream of Zelienople, Pennsylvania. During Hurricane Ivan, 45 homes there were flooded. And part of the reason they were flooded is because of what’s called the backwater effect. It’s like sticking a plug in a bathtub, filling it full of water, and then when you get in and sit down, the water rises. The same thing happens in nature when you have a dam that slows the flow of the water and it can’t go on down through the stream. And so what we had at the Harmony Junction dam was a backwater effect that caused the stream banks to overflow. The fire department and police department actually had to go out in boats and rescue people during Hurricane Ivan because of the flooding. We removed that dam in 2009, and we’ve since had two storm events that equaled the flow of Hurricane Ivan. The stream has gotten out of its banks, but it has not flooded any places. The community did go through a buyout program through FEMA; the properties were acquired and the homes were moved out of the way to prevent future flooding. But if you look at where the water level was post-dam removal, if those homes had stayed, they probably would have been safe during other storms.

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Lisa Hollingsworth-Segedy is Associate Director of River Restoration at American Rivers. You can read more about American Rivers’ efforts to remove dams in their recent report.