Flooding is the most common natural disaster experienced in the Lake Champlain basin. The basin’s wet climate, steep mountains and narrow river valleys make it highly susceptible to both minor and major flooding events. Flooding is a natural function of water moving through our mountainous watershed – but changing precipitation patterns, development in flood prone areas, and historic mismanagement of our rivers have made floods more dangerous and destructive to our communities.
As heavy precipitation events become more frequent in the Lake Champlain basin, our rivers are not able to absorb and slow this excess water because many of the basin’s rivers have been straightened and disconnected from their natural floodplains to accommodate development. Without access to floodplains, our rivers flow fast with destructive force. This poses a serious risk for communities through which streams and rivers flow, and it accelerates the flow of contaminated flood water into Lake Champlain.
The Lake Champlain basin experiences frequent localized floods caused by rain events all year round, but springtime can predictably be a time to look out for flooding. In the winter, much of the precipitation the basin receives is stored as snow and ice in higher elevations of the basin. As winter turns to spring, much of this snow and ice stored up high in the mountains will melt and drain into Lake Champlain. Lake Champlain usually reaches its peak water level in May when it absorbs the last of winter’s snow melt and spring rains. Flooding events in rivers and streams are intensified by springtime temperatures that fluctuate well above and below freezing. This can speed up or stop flow as ice, snow and water interact. Snow covered ground acts like a speedy runway for rainwater entering rivers and streams, giving them added power. Chunks of ice can pile up in rivers, forming ice jams that divert, slow or stop water flow.
In addition to these seasonal and localized floods, there have been several large-scale flooding disasters in the last century that have had substantial impacts on basin communities, the Lake, and its tributaries. These have influenced people’s mindsets around flood resilience. Heavy rainfall over three days in early November of 1927 brought one of the greatest disasters in Vermont’s history. This is now known as the Great Flood of 1927. Floodwater covered towns, destroyed infrastructure and claimed 84 lives. The basin experienced flooding of comparable magnitude in 2011. Lake Champlain reached a record level of 103.2 feet in the spring, inundating lakeside communities. Then in August, Tropical Storm Irene brought torrential rain and destructive flash flooding to the basin. Thousands of homes and businesses experienced long term power outages, substantial damage and destruction from the massive flooding. Just twelve years later in July of 2023, continuing rounds of heavy rain fell on saturated soils and overwhelmed the basin’s waterways. This produced historic flooding reminiscent of Tropical Storm Irene.
