not just the Columbia, have you ever seen the Siuslaw on a weekend day in September?
most fishing kayaks are self draining SOT (sit on top), so spray skirt doesn't apply, but very important is a tall orange ATV flag and since I go out in early low light/foggy conditions, I also have a white LED boat light on the back of mine...and a handheld floating VHF radio is nice to have.
the boat wakes are not a danger on coastal rivers (no barges like the Columbia has) but I have an issue with other boaters that do not know the rules: within 100 feet of an anchored or manually powered boat you are limited to 5mph.
so think about the 10 yard markers on a football field, 3 of those get you to almost 100 feet, if you are going to pass within that distance of a kayak/canoe/driftboat using oars, you must slow to 5mph. last I checked the ticket was just over $400 dollars, so worth taking note of. (FYI- the 5mph limit is 200 feet from a swimmer, surfer, wading angler, dock, floating home or boathouse.)...
cheers, roger