Photo of the former impounded area, where West Brook is...

Photo of the former impounded area, where West Brook is recarving its former channel and a riverside meadow is taking hold. Credit: Enrico G. Nardone

This summer, a dam on West Brook in Islip partially failed and drained the man-made lake known as West Brook Pond. For the first time in more than 100 years, the stream was able to run unobstructed from its headwaters in Bayard Cutting Arboretum State Park to the Great South Bay.

This might sound unremarkable, but of the more than 100 rivers and streams on Long Island, only a handful could make such a boast. In the past, most were dammed to power mills, for harvesting ice and cranberries, or for irrigation or recreation.

While few of these dams still serve their original purpose, all continue to impose a significant ecological cost. Dams destroy riverine connectivity, prevent the movement of wildlife, heat up impounded and downstream water, and trap sediments that are needed downstream. Most damaging, however, is the impact the dams have on river herring and American eels — native fish that need to move between fresh and salt water. Dams have largely eradicated these fish from Long Island, eliminating the vital role they play in transferring ocean energy and nutrients into our bays, rivers and streams, and in providing forage for everything from osprey to striped bass to seals.

Yet dams also impose a significant economic cost. First, there’s the basic maintenance of aging infrastructure that in most cases is many decades old. This work is low priority and is generally deferred until problems arise. But the clock is ticking and repair costs are rising.

In the meantime, there’s the plant problem. All dams trap sediments; as they do so, they get shallower and eventually provide habitat for aquatic (often invasive) plants to grow and choke out the open water. This overgrowth interferes with the things people appreciate about ponds and lakes: water views and places to fish, boat and swim.

The cost of addressing excessive plant growth isn’t trivial. In 2013, a project to dredge sediments from Upper Lake on the Carmans River cost more than $4 million. Other efforts to drain impoundments and mechanically dredge sediments have been similarly expensive.

The problems associated with aging dams are not isolated — across Long Island there are hundreds of artificial lakes and ponds facing the same problems. But what can be done?

One option is to spend tens of millions of taxpayer funds on costly solutions to maintain the status quo. This expenditure would be a temporary solution, of course — the problems will return in years or decades as sediments continue to fill these man-made lakes and ponds and aquatic plants continue to choke them.

The other — sensible and pragmatic — option is to move beyond the legacy of dams. Instead of investing in obsolete infrastructure that has long stopped serving its original purpose, the time has come to let some of our rivers and streams run free. Doing so would improve the health of the waterways and benefit our overall coastal ecosystem. It also would save many millions in taxpayer dollars. Not every dam needs to be removed, of course, but it’s time to embrace a policy that recognizes that dam removals often serve the greater public interest.

As municipalities across the country have increasingly recognized this reality, thousands of dams have been removed over the past decade. While there has yet to be an intentional dam removal on Long Island, a few dams damaged by storms were not repaired. Two of these de facto dam removals happened in state parks and both produced positive, ecologically beneficial results.

Now, with the storm-damaged dam at West Brook, the state parks department has another opportunity to lead. It should seize this opportunity and allow West Brook to run free to help Long Island move past the costly legacy of aging dams.

Enrico G. Nardone is executive director of the nonprofit Seatuck Environmental Association.

DON'T MISS THIS LIMITED-TIME OFFER1 5 months for only $1Save on Unlimited Digital Access