The issue is not sealing off the border entirely, but trying to reduce non-essential travel while keeping supply chains and essential commuter workers flowing. A person who's no longer able to make their weekly milk run to Bellingham, WA from Surrey, BC isn't going to try hiking across the border, but it'd be best if they could be persuaded to stop travel voluntarily without incurring the costs to essential traffic that come from closing border crossings.

+1

This isn't a police action to prevent dirty immigrants from getting across the border, it's a quarantine measure.

99% of those travelers aren't going to row across a lake to get into Canada; if they are chances are they're doing something sketchy and would have been rowing across lakes anyway regardless of the enforcement regime.

More importantly disease transmission is one of herds and numbers -- a tiny handful getting across isn't a huge deal, it's the influx coming through ports and via plane.

The precedent from European countries has been to exempt people who commute across the borders from the shutdown; I imagine that Canada is likely to go the same route here.

I stopped commuting across the border just a little while back. For years I'd crossed it every day.

I feel like I just slid under the door in Raiders of the Lost Ark.

There is also the tiny peak in Minnesota which is only accessible by boat or Canadian road.

There's one of those in Washington too.

The folks in Point Roberts are going to have a hard time if the Canadian border is closed to US citizens. If the US does the same, a good number of Vancouver residents will lose access to their US post office boxes. Guess someone will start a ferry between Point Roberts and the rest of Washington.