Climate-Change Floodwaters Threaten People & the Environment

By Michael J. Caduto

(This is the third in a series of articles looking at the nature and history of the Ottauquechee River and human impacts on the watershed.)

Erosion at Sustainable Woodstock’s Community Garden at Billings Farm during the Great Flood of 2023. This riparian buffer is in the midst of a multi-year process of being redesigned and restored. Growing space will be expanded on the opposite side of the garden to offset what was lost along the riverbank. Photo by Michael J. Caduto

From the Green Mountain State to California, many regions are experiencing more frequent and severe precipitation events because the atmosphere is holding more moisture due to warmer temperatures. Globally, flood-related disasters have increased by 134 percent over the past 25 years.

On July 10-11, 2023, Vermont was hit with yet another major deluge from extreme heavy rainfall catalyzed by the meteorological impacts of climate change. The National Weather Service dubbed Vermont’s recent catastrophe The Great Vermont Flood of 2023. Over this two-day period some parts of Vermont, including Ludlow and Plymouth, received more than 9 inches of rain, washing out roads and bridges and flooding homes, cities, villages and farms. Damage in central Vermont exceeded that done by Tropical Storm Irene in August 2011. In order to find a storm whose impact was worse than these two recent meteorological maelstroms, one has to go back to the Great Flood of November 3-4, 1927.

At the height of the floodwaters last July, I went to check on the erosion where Sustainable Woodstock’s Community Garden at Billings Farm borders Barnard Brook. A significant strip of the northeast corner of the garden had been carried away, in some places cutting the edge of the 15-foot tall riverbank back by about 8 feet and carving into the part of the garden used to grow food for the Woodstock Community Food Shelf and Upper Valley Haven.* As I was salvaging a length of solar electric fence that had slumped over the riverbank, and fearing how the silt and nutrients being washed into the Ottauquechee River would impact aquatic life, I was hit by a wave of foul odor—a combination of septic and fish. That was when I realized how severe the water quality crisis created by the flooding had become.

Public service announcements caution to avoid downed power lines and admonish against driving through water that is covering roadways, but the health hazards of floodwaters are severe and can linger for weeks after the water levels return to normal. According to the Centers for Disease Control and Prevention (CDC), contaminated floodwater can cause a range of serious health conditions, including skin rashes, infected wounds, tetanus and gastrointestinal illness. If you see the rainbow hues and inhale the petroleum scent of No. 2 fuel oil from a riverbank during flooding, it’s common sense to avoid any contact with the water, let alone contemplate catching and eating fish.

Hazardous materials were reported to have been washed into rivers and lakes in more than 200 locations around Vermont, ranging from fuel tanks to wastewater overflows and nutrients from eroded soil, but the exact quantities that entered waterways could not be determined. Raw or partially treated wastewater entered waterways from more than two dozen wastewater treatment facilities in towns throughout Vermont, including Bridgewater. The wastewater treatment facility in Johnston was completely destroyed.

In addition to bacteria and pathogens, wastewater effluent contains nutrients in the form of phosphorous and nitrogen. These nutrients cause blooms of algae in the water, including toxic blue-green algae (cyanobacteria). Fed by excess nutrient levels during and after a flood, algal growth skyrockets. When the algae die, the process of decomposition uses up significantly higher levels of oxygen in the water, causing extremely low levels of this life-sustaining gas and threatening other forms of aquatic life. Accentuating the problem, the warmer waters that we’re experiencing due to climate change increase the impacts of nutrient overload by accelerating the growth of algae.

As floodwaters erode riverbanks, enormous volumes of sand, silt and loam are carried away. This silt poses serious problems for freshwater life, coating the gills of fish and aquatic insects. Silt clouds the water and reduces sunlight penetrating to the river bottom where it is essential for growth of the natural algae that forms the base of the aquatic food chain. In this way, the combination of low oxygen levels and less sunlight severely impacts the health of aquatic ecosystems.

So when the next flood hits us, avoid contact with the water, and cease fishing, until health officials have deemed it safe again. Long-term solutions include restoring and replanting riparian zones which reduce pollution entering waterways, mitigate flooding and reduce erosion and siltation.** Separating wastewater and stormwater systems will help to prevent the extreme and sudden inflows of stormwater during flooding from overwhelming wastewater treatment facilities and washing wastewater into our waterways.

And, of course, everything we can do to fight the advancement of climate change will help to reduce the numbers and severity of floods going forward.


*This video, taken on July 11, 2023, shows damage to Sustainable Woodstock’s Community Garden at Billings farm done by the Great Flood of 2023:

**See the article on The Benefits of Protecting Riparian Buffers in the May 18, 2023 issue of the Vermont Standard (page 8C).

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