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Study Board Holds Meetings On Lake Champlain Flood Mitigation Options

Lake Champlain flooding May 2011
Vermont Governor's Office
Lake Champlain flooding May 2011

The International Joint Commission Lake Champlain-Richelieu River Study Board held a series of virtual hearings this week in English and French to update cross-border interests on a study investigating potential flooding mitigation options for Lake Champlain and the river it flows into.
In 2011, flooding throughout the Lake Champlain and Richelieu River basin had the highest lake levels and river flows recorded in the past hundred years. Lake Champlain remained above flood level for 68 days.  The International Joint Commission, or IJC, was formed in 1909 to regulate U.S. and Canadian boundary waters.  In the wake of the flooding the U.S. and Canada requested the IJC create a plan to improve flood forecasting, preparation and mitigation.

U.S. study chair Deborah Lee provided an overview of the status of the study. She first described the watershed and damage incurred in the 2011 flooding.  “The area of the LCRR watershed covers more than 9,000 square miles. Eighty-four percent of its watershed is in the United States in New York and Vermont and 16% is in Canada in southern Quebec. The Richelieu River in Quebec must carry the runoff from the large watershed area draining to Lake Champlain. As a result of the 2011 flood 4,000 homes were damaged. More than 30 municipalities were directly affected and approximately $82 million in damages were experienced with more than 80% in Quebec and less than 20% in New York and Vermont.”

Lee said to address flooding the study is exploring a range of physical mitigation options. She outlined the six preferred options that have been reviewed including dredging at the St. Jean Shoal to remove obsolete man-made structures; diverting water through the Chambly Canal during flooding; implementing both those options or setting up different types of weirs along the Richelieu River.  Lee said the board will focus on the first two and is particularly interested in the potential for diverting water into the canal. “The diversion would only be used during a flood. There would be no impact otherwise.  If flooding were like the spring of 2011 the diversion would reduce water levels about a foot at St. Jean-sur-Richelieu and about 6 inches or half a foot on Lake Champlain at Rouses Point. And based on preliminary estimates it’s expected this work would cost between $63 and 77 million.”

The potential to enhance wetlands as potential natural mitigation measures was a key topic during the meeting’s open discussion session.  “It’s Patrick Ragaz with the Mohawk Council of Kahnawake. The existing wetlands do have an important role to play in reducing the flood stage. I’m just wondering if those are protected at this point or if there’s a role to play for building some additional wetlands to just include some redundancy in the existing system?”

Alain Rousseau is a professor at the Eau Terre Environnement Research Centre in Québec City specializing in hydrological modeling and water management.  “We did look at simulating a scenario which was essentially adding 650 square kilometers (250.9 square miles) of wetlands in the Lake Champlain basin. And it could provide additional relief with respect to reducing the water level by about four centimeters (1.574 inches) with respect to the 2011 flood. Mind you that could be viewed as minor for the Lake Champlain but when you do add wetlands in the 18 major tributaries to the lake you could have important local effects that could alleviate local flooding in those areas.”

A report on the use of wetlands in upland areas as a potential option for flood mitigation in Lake Champlain and the Richelieu River is expected before the end of 2020.

Final recommendations are expected to be submitted to the International Joint Commission in the first quarter of 2022.


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