16 Dec
2014

Posted in: Dam removal, land trust, Natural Science, Rhode Island DEM, RINHS, The Nature Conservancy, US Fish and Wildlife, USFW, Westerly, White Rock Dam, Wood Pawcatuck Watershed Association, WPWA
By Hugh    No Comments

REMOVING DAMS TO RESTORE NATURE

Nils Wiberg, engineer from Fuss and O’Neill details the White Rock Dam removal project.

It seemed like the right move at the time. Big factories like textile mills in the 18th and 19th centuries needed power, and when there was no such thing as electricity, there was one major source: water. Use the power at hand to make a factory generate products. Build a factory by a river. Dam the river, turn it, shape it, bend it to the needs and turn that enormous force into the materials that would build America. Fish might not be able to get past the dams, and it seemed like heavy rains caused more problems than they used to, but that was a small price to pay for generating power.

Fast forward to the 100-year floods of 2010. Hurricane Sandy of 2012. Two of the most significant weather events to hit Rhode Island in decades. In Charlestown alone, Sandy saw to it that there were only six houses in the whole town with lights on at night. But the biggest impacts were from water. A report from the Wood Pawcatuck Watershed Association (WPWA) states the three storms in March 2010 dumped over 16 inches of water on the state. Damage from Sandy was well into the tens of millions of dollars. That damage was due in part to the dams built so long ago, now obsolete but still obstructing rivers, and still changing fish migration habits. Still causing floods.

Plans are forming around the state to do what will soon be happening in Charlestown: take down the dams. At a public information workshop last Wednesday, a packed house of more than 60 people learned that a dam built in 1770 will be taken down soon, and its impact will have major positive results for the town. With federal disaster relief funds, the White Rock Dam will fade into memory in less than a year, even as the natural course of the river is restored. While the White Rock removal will impact a particular part of the state, the process and benefits are worth examining by others who may be curious as to the benefits of such a process.

“We looked at the history of this river from the earliest maps and aerials we could find, and we looked at what the dynamics are of this river and what is likely to happen once the dam is removed.” Nils Wiberg, engineer with Fuss and O’Neill, the firm hired to do the analysis of the project spoke to the audience at the Westerly Police Station community room. In attendance were representatives from The Nature Conservancy, the Wood Pawcatuck Watershed Association, D.E.M., and other agencies involved with the project.
One major impact on the area will be the raising of the flood plain upriver.

Like any dam, the White Rock causes water to accumulate not just at the dam, but far upstream as well. That means that when the region is impacted by heavy rain, the section upstream is much more likely to overflow its banks, because the river is already high, and has no way of moving the water any faster. That was the case across the state in 2010, when places like Warwick Mall flooded so badly that it was forced to close for months to repair the damage, costing businesses millions in lost sales. Once the dam is removed, the flood elevation will be increased, since the water will be readily able to move excess rainwater down to the sea. The change will result in protecting homes, businesses, and roads within the current flood plain.

Another common issue with dams is the impact they have on fish migration. Alewife, blueback herring, American shad, and many other fish are anadromous, meaning that they spawn in fresh water. Following hatching, the young make their way to the ocean. Once sexually mature, at roughly a year or two old depending upon species, anadromous fish will migrate to the place where they hatched to lay their eggs. However, a river that is dammed means the fish either have great difficulty returning to their spawning grounds, or never get there at all. If the area near the dam is passable at all, the water flowing downstream is moving too quickly to allow most fish to get through. Those that do are often so exhausted that they die in the process of trying to return. Removal of the dam means that the flow will return to its natural state, enabling the fish to complete their cycle. D.E.M. biologist Phil Edwards says that, with “seeding” of fish in Warden’s Pond, those passing through the restored river may begin returning to spawn as quickly as 2016.

Some at the meeting expressed concern that lower water surface elevations will affect animals such as beavers upstream from the dam. Engineer Wiberg indicated that negative impacts were unlikely: “Beavers will still have the river to move in and out of. It’s going to be what was here before the first dam was built 250 years ago. I’m sure the beavers were quite happy with the river then, and I think they’ll find a way to live with the river going forward.”

Fish have found it difficult or impossible to propagate at sites around the state. Home and business owners are finding themselves dealing with an increasing number of flood issues. What will happen at White Rock is a goal that may be attained at sites around the state as more projects are examined. Nils Wiberg put it this way: “We can work with Mother nature on this river, so she can do what she wants to do, so we can minimize the flood risk, and facilitate the passage of the fish.”