Lake Look: Flooding and Climate Resilience in the Lake Champlain Basin

AUGUST 2023

The floods of July 2023 brought devastation to so many throughout the Lake Champlain Basin—they inundated homes and businesses, destroyed crops and livelihoods, and washed away roads. On paper, it will be a costly recovery, but the true cost of the destruction cannot be measured in money alone. Rivers throughout the basin rushed to levels not seen in nearly 100 years, with staggeringly high flow ultimately pouring into Lake Champlain. What did the rivers carry, what does this mean for the lake, and how can we be more resilient in the future? 

Rivers carried just about anything that floats. Pollutants of all manner swept into the lake. Building and auto parts, propane tanks, and large trees were all witnessed in the raging waters. The tires and other trash—if not removed—will ultimately sink to the bottom of the lake and leach their chemicals and metals causing more ecological harm and threatening aquatic life. The large trees will take a long time to break down and can actually be beneficial for fish and amphibians as they provide habitat in which young fish can hide. However, long after floodwaters recede those same trees can provide hazards to boaters and swimmers as they lurk below the surface and are difficult to see, especially in murky water. Recreationalists need to be cautious, particularly near river deltas.

While this visible debris is a major challenge, an even greater concern in terms of water quality and safety is that which is invisible to the naked eye. With excess water overwhelming wastewater treatment facilities in many Vermont communities, combined with a sewer main break under the Winooski River that alone dumped an estimated three million gallons before it could be diverted, untreated sewage and the associated fecal coliform bacteria flowed into Lake Champlain. Farms throughout the basin were flooded as well—a tragedy for farmers and local food systems, as well as water quality due to the huge quantities of sediment, manure, and nutrients that entered waterways. This, combined with the wastewater, resulted in beach closures and will have an impact long after the flood waters recede.

When entering the lake, the turbid floodwater blocks sunlight cutting off photosynthetic cyanobacteria from the source necessary to make food, resulting in a short-term decrease in blooms. The storms also created wind and wave action that can further disperse and dilute cyanobacteria. However, in the weeks following while water settles, cyanobacteria blooms will likely increase because of the additional phosphorus—one of the nutrients that drives blooms—were bound in the sediment that muddied the floodwater. Early estimations are that Lake Champlain received a year’s worth of phosphorus loading from the event and that some rivers delivered more phosphorus to Lake Champlain during the July 2023 flood than during all of 2022.

We are seeing the direct effects of the climate crisis in our region. Warmer air temperatures increase the atmosphere’s capacity to hold greater quantities of water vapor and with more water vapor comes more rain. This has already been happening in the Lake Champlain Basin: in the past 30 years, the frequency of storms with over an inch of rainfall has increased by 75% in Vermont, and New York cites increased heavy precipitation events as a major impact from climate change. The July 2023 flood came 12 years after Tropical Storm Irene (the State of Vermont completed its last recovery project from that disaster just a few months ago) and less than four years after the 2019 Halloween storm. The Winooski and the Lamoille Rivers crested higher during this recent event than during Tropical Storm Irene. It is no longer accurate to call these events “100-year floods”. This will not be the last big storm or flood in the Lake Champlain watershed. 

The Intergovernmental Panel on Climate Change (IPCC) defines “climate resilience” as the capacity of social systems, economies, and ecosystems to cope with a hazardous event or trend or disturbance from climate change. For ecosystem and economy alike, wide undeveloped floodplains are critical in this endeavor. Flooded rivers will fill these floodplains no matter what is in them. When those areas are comprised of vegetation adapted to periodic flooding, the waters are retained and have the chance to soak into the ground. When floodplains are developed, water cannot soak into the ground and structures are at risk of damage. The Lake Champlain Committee (LCC) is a partner in a new program called Stream Wise. Organized by the Lake Champlain Basin Program, Stream Wise helps people who live near streams and rivers maintain a healthy stream buffer (which are essentially mini floodplains). Wide and healthy stream buffers create climate resiliency by giving floodwater space to spread out and soak into the ground. LCC will conduct landowner assessments of stream buffers focusing on the Chittenden County metro area—learn more and sign up here.

In the wake of the July 2023 flood destruction volunteers and donated goods are flowing into affected communities with a force and momentum equal to the storm surge. It is heartening to see so many people reaching out and stepping up. That community spirit is critical now and it will be in the months and years ahead as we work to recover.

The sewer main that broke under the Winooski River was built in the 1950s—at a time when the July 2023 flooding was not conceivable. That is no longer the reality we face. While we have made important headway in advancing regulations, policies, and protections since Tropical Storm Irene, there is much more to do. That work will take an active, engaged community. Let’s keep the momentum of caring that’s showing up with such force in the wake of the July 2023 floods going.