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The Dartmouth
May 26, 2024 | Latest Issue
The Dartmouth

Bryant: Leave Dams Be

Flood-control dams protected livelihoods across New England this past summer — as long as they remain structurally sound, they should not be removed.

This past summer, FEMA allocated more than $14 million in flood relief to Vermont residents. In the town of Barre, Vermont, floodwaters from a branch of the Winooski river destroyed hundreds of homes, businesses and livelihoods. And yet, the non-profit Friends of Winooski River has plans to remove several dams in the Winooski watershed. As of 2021, more than 140 dams have been removed from Vermont’s waterways. 

Thanks in part to the remaining several hundred small, non-hydroelectric dams in New England — which control more downstream river length in New Hampshire than in Vermont — New Hampshire did not suffer the same degree of disastrous flooding that Vermont did this past summer. I argue that, as climate change increases catastrophic flood risk, Vermont state officials should not remove functioning flood-control dams when the benefit to livelihoods outweighs environmental costs.

In the early spring months of 1936, a series of extraordinary thunderstorms dumped dozens of inches of rainfall across New England. As part of former President Franklin Delano Roosevelt’s New Deal, and in response to this extraordinary flooding, Congress passed the Flood Control Act in June 1936. The Act authorized the Army Corps of Engineers to build dams across the country, including those in the Connecticut River Watershed. 

The Act, in keeping with its name, also requires that dams achieve a favorable cost-benefit ratio on the merits of flood control alone, without additional hydroelectric power. According to the Act’s sponsor, Senator Royal Copeland, D-N.Y., hydroelectric power production is incompatible with flood control from an engineering perspective. Flood control reservoirs require relatively low water levels to accommodate flood waters, whereas hydroelectric dams need higher water elevations for maximum efficiency. As a result of this stipulation, the Flood Control Act authorized many small-scale, simple and inexpensive dams whose sole purpose was flood-control — like the Union Village Dam in Thetford, Vermont. The evidence is clear that these projects have been extraordinarily cost-effective. The Union Village Dam, for example, was built in 1950 for $4.1 million, but has prevented an estimated $56.6 million in damages as of September 2011. 

Though scientists do not yet fully understand the causes of the catastrophic flooding this past summer, these projects on the Connecticut River Watershed likely prevented millions of dollars in damages in New Hampshire and Vermont. Where the human cost of flooding was highest, in Barre along the Stevens Branch of the Winooski River, there is no upstream flood-control dam. Vermont officials should not remove flood-control dams that will save many times their construction costs by preventing property damages and saving livelihoods.

For a watershed as densely populated as the Connecticut, these kinds of dams are extraordinarily valuable to nearby communities. The Union Village Dam alone supports a semi-rural neighborhood directly downstream. There are residences, a community center and recreational areas within 200 yards of the dam itself, which would face the threat of flooding if not for the dam.

Though they will safeguard communities from disaster, these small flood control dams are not without serious reasons for removal. First, some dams become structurally unsound as a result of age or mismanagement. In dire cases, of course, removal may be the best strategy. In others, though, the dam may be able to protect downstream communities from flooding, and refurbishment and maintenance of the dam is the best course of action. Along the Winooski, for example, officials should refurbish rather than remove dams and consider building a flood-control dam north of Barre to prevent future flood damage. 

Second, dams may encourage further development on the floodplain, which will only increase the magnitude of flood-caused property damage. In flood-prone areas, it may be better to allow flooding to continue unchecked and thereby prevent vulnerable human development.

This strategy, unfortunately, will become less viable as climate change worsens the frequency and intensity of flood events and the precipitation that causes them. Developed areas that were previously safe from flooding will come under threat, and maintaining dams for flood control is the most cost-effective adaptation. Demanding that residents abandon their homes and livelihoods is completely untenable. Without flood-control infrastructure, existing development will face repeated property damage from uncontrolled flooding.

Third, research shows that dams irreparably harm riverine ecosystems by disturbing natural hydrological and sedimentological conditions. For example, fish spawns are hampered by a low supply of nest building material and a lack of flood pulses. Dams can also result in greenhouse gas emissions through the accumulation of biomass in large reservoirs.

These are serious reasons to remove dams, but these downsides can be mitigated by technological and managerial improvements. First, when dams are used only for flood-control, their reservoir levels are kept low (unlike hydroelectric dams), which mitigates the harmful ecological and climate impacts upstream of the dam. The reservoirs destroy less habitat and accumulate less GHG-emitting biomass. Second, it is an active area of research to find better dam management programs that mitigate harmful downstream impacts of existing dams. If the dam allows sediment to pass through unobstructed at regular intervals, for example, harmful downstream changes in sediment composition may be minimized. 

We have the foresight of the Flood Control Act of 1936 to thank for the Upper Valley’s relative safety this past summer. Vermont state officials face a similar situation today, where changing environmental and economic conditions require infrastructural response. Though the ecological, environmental and economic benefits of dams are complicated at best, they should be maintained and refurbished in instances where the risk to human livelihoods is extremely high. Especially in wet, densely populated areas like New England, flood control dams will continue to pay dividends far into the future.

Opinion articles represent the views of their author(s), which are not necessarily those of The Dartmouth.