it sounds to me like what they need is a dam up the ottawa to slow the tributaries down. i guess that at the time they built the seaway, ottawa was mostly just sending logs down the river, and nobody was really worried about climate change.

if you need a dam, it's worth a turbine.

this is actually a good example of what i was hoping the infrastructure bank would be used for.

https://www.theweathernetwork.com/news/articles/flooding-along-st-lawrence-could-worsen-if-ny-politics-wins/82113/