Section 4: Study Recommendations and Advice

4.1 How will the Study's recommendations be implemented when the study is over? 

The Governments of Canada and the United States asked the International Joint Commission to develop and recommend various mitigation measures to reduce impacts of future flooding within the basin. 

The Study Board expects to deliver its final report to the International Joint Commission in March 2022, after which the Commission will recommend preferred measures and implementation approaches to the two federal governments. It will then be up to governments and stakeholders to take action on these recommendations. 

4.2 How long will it take to implement measures that are recommended by the Study Board and the IJC? 

The IJC will present recommendations to governments based on the final report of the study in 2022. Local, state, provincial and federal governments will decide what measures they may wish to take, based on the data and recommendations from the study.  Both structural and non-structural solutions may be recommended by the study, some with much longer timelines for implementation than others. 

4.3 What can property owners along the Lake Champlain and Richelieu River shorelines do to protect their lands and help mitigate flooding? 

Property owners can prepare themselves and their properties against flooding by staying informed about local floodplain management policy and being aware of emergency response measures in their localities. It is also important to rely on accurate and reputable sources of information. More information on this is available in the Study Board’s Spring Flooding Fact Sheet. 

Other considerations are to investigate options for flood-proofing homes and developing personal flood response plans. In some instances, considering the installation of a vegetative buffer between the shoreline and private structures is another option. Implementing green infrastructure such as vegetative buffers are often preferable solutions to building hard infrastructure such as sea walls.  

4.4 What types of structural solutions are the study board considering as part of its final recommendations?

The Board assessed a variety of moderate structural solutions that could reduce the impacts of flooding in the basin, using a rigorous evaluation criteria. Two options have emerged as front runners of possible implementable solutions.

The first is the selective excavation of a shoal near Saint-Jean-sur-Richelieu which could reduce maximum flood levels by 15 cm (6 inches) at Saint-Jean-sur-Richelieu and 11 cm (4 inches) on Lake Champlain. Simultaneously, construction of a submerged weir in the Richelieu River would sustain water levels in the lake during low water periods.

The submerged weir (Figure 1) would act like an artificial rapid. Using rocks excavated from the shoal, the weir would be constructed and extend halfway across the river. The rest of the river would be reshaped to approach the existing natural river bottom to 28.35 m (93.0 ft.). (93.0 ft.).This would constrict flow during low water periods, increasing water levels on Lake Champlain by as much as 30 cm (1 foot) from current low water levels. The weir’s trapezoidal shape would minimize sediment build up on its upstream side and would allow for passage of aquatic species. The locations downstream of the submerged weir will never go dry and even the lowest observed discharge will flow over the structure. The weir would have no doors or moving parts. During high water periods, more water would flow over the top of the weir, increasing the volume of water moved by the river and minimizing flooding.

The second is the above option combined with a moderate diversion (approximately 80 cms, 2,825 cfs) during a flood event through the Chambly Canal.  The flow is directed from the river into the canal via four box culverts and discharged back using five box culverts. The river flow is diverted into the canal and then exits the canal about a kilometre downstream where it discharges back into the river below the shoal ( Figure 2). This option provides additional water relief and reduce flood levels in an event like 2011 by 22.5 cm (8.8 in) at Saint-Jean-sur-Richelieu and 14 cm (5.6 inches) on Lake Champlain.

Both these alternatives help move the system closer to an earlier natural state before most of the human interventions in the river environment.