The Lake Champlain-Richelieu River basin straddles the United States and Canada between Vermont, New York and Quebec. There have been numerous floods in the basin, but work is ongoing to develop an operational real-time flood forecasting and flood inundation mapping system.
The outflow from Lake Champlain is controlled by a long natural barrier, the rock shoals at Saint-Jean-sur-Richelieu. This barrier reduces the flow of the river so that the water level rises during the spring melt-off. These high water levels are responsible for floods in low-lying regions around the lake and adjacent to the river. This can be exacerbated in the spring by sudden high temperatures, prolonged precipitation and high winds.
In the basin, record floods were set as early as 1869. In the spring of 2011, the lake level rose to 103.2 feet, which had an extreme impact on the people and resources of the basin’s ecosystem, with about $88.5 million (U.S.) in reported damages.
A total of 79 percent of damages were recorded in Quebec, with the remaining 10 percent in Vermont and 11 percent in New York. Waters exceeded flood stage on April 13, 2011, and remained there until June 19, 2011 --- a total of 67 days.
Options for Flood Mitigation
Considerable damage to agriculture lands and residential and commercial properties has engendered a number of citizen complaints and assistance requests from governments over the years. On several occasions, governments have requested the International Joint Commission (IJC) to more fully study the basin and investigate possible options for flood mitigation.
Debate and discussion still prevails around whether the levels of Lake Champlain should be artificially regulated. One point of agreement seems to be that there’s still much to learn about the science governing the system before we make decisions about potential mitigation measures.
In 2012, the governments of Canada and the U.S. requested that the IJC review and make recommendations regarding a comprehensive study of measures to mitigate flooding and the impacts of flooding in the Lake Champlain-Richelieu River watershed.
In response, the IJC provided a Plan of Study report in 2013. Based on the Plan, governments have since requested that the IJC address data gaps in our knowledge of the hydrology of the basin and produce inundation maps.
This work and a report were produced by a Technical Working Group (TWG) of bi-national experts established by the Commission in the fall of 2014. The work performed under this request has generated, compiled and analyzed new and available data toward an operational real-time flood forecasting and flood inundation mapping system.
Further work is needed to complete the system, but it’s central to the exploration of potential flood plain management solutions and a range of structural and non-structural flood prevention and mitigation measures.
New data and innovative products have been produced from this binational effort.
With available data, a new 2-D hydrodynamic model of the basin was generated capturing all of the hydrological features not taken into account in the past. These features include: causeways on Lake Champlain, which cause pinch points (a narrowing where water flow is restricted), and the old Fryers dam downstream from the town of St-Jean, which restricts flow because of the 30 concrete pillars that span the width of the Richelieu River.
Improvements were made in the assessment of meteorological parameters which enhanced prediction of short- and long-term precipitation, wind and temperature for the basin. This is important for risk management and mitigation as it increases the predictability and reliability of forecasts for flood modeling purposes. The difference between the vertical datum (surface elevation of an object relative to sea level) was solved. The difference stems from jurisdictions using different standards and data interpretations resulting in physical objects being geospatially misaligned at the border. Again, this work has served to decrease the uncertainty in flood forecasting predictions in the basin.
In coordination with the Technical Working Group, the IJC developed a Web-based application that displays each of the inundation scenarios outlined in a draft report.
The online product portrays inundation in the basin based on 11 water elevations of Lake Champlain and includes the 2011 lake level of 102.8 feet (31.3 meters). It depicts the areas flooded, the depth of the flood and the aerial uncertainty in prediction.
A month-long public comment period ended in December 2015, following targeted user group information sessions in Burlington, Vermont, and Saint-Jean-sur-Richelieu, Quebec. The products are targeted at those who would use the products in their work such as emergency responders, community planners, municipalities, and public security organizations. Meeting participants expressed support for the products and provided helpful comments.
Building on the need stated by users and the public to pursue the Plan of Study, two possible scenarios are envisioned by the IJC. The first is to facilitate the coordination and completion of a real-time forecasting system for the Lake Champlain-Richelieu River basin. The second is to work on parts of the Plan not covered in the original request, such as the evaluation of past impacts, management practices and adaptation strategies, and to assess easy to moderate flood mitigation measures and their impacts.
The results of this study are consistent with current efforts by governments to have the most current and credible scientific information in hand to mitigate flood risks and properly plan emergency responses. The IJC recommends that this real-time forecasting system be completed for the entire Lake Champlain-Richelieu River basin.