Simpson River - This is a great day trip in the spring. There's about 8km of river that is paddleable on the Simpson before it meets the Vermillion (which runs into the much better known Kootenay). There's a hiking trail that goes up the river valley. The trail will get to a point where there's an obvious canyon that has a few bends and is choked with wood.
We started just below this canyon but I have seen other blogs starting higher up for multiday trips. It doesn't seem worth it and this is likely the best stretch with the least wood.
There are no big rapids but it is continuous, shallow, and woody. You'll need good reactions and be prepared to avoid woody surprises.
I would not recommend for non-grade 3 paddlers due to the wood potential.
If you're in the area for a while, combine with some of the Vermillion of Kootenay. It won't be possible to run this until Kootenay allows watersports again.
Park at the Simpson River Trailhead. You can take out at the confluence of the Simpson/Vermillion and walk a short ways back on the highway shoulder to your car.