Helmets - River kayaking

I am thinking about floating the Kasilof River here in Alaska.  It's a fairly tame asy by almost any standard float.  But there are a few rocky sections and I can see that if I am going to get in trouble it'd be through these boulder fields.

So do I need a helmet?  If I have to ask, i think the answer is yes.  I obviously have done some ocean fishing but this flowing water thing is totally new to me.

Thoughts?

I don't think it would hurt. If there really are rock gardens you'll be floating through, you might spare yourself some pain.

If it is low gradient with gravel riffles, there's probably not much of a threat for the helmet to protect you from. (Bankies casting big lures at your head?  )

Some of the guys launching through surf are wearing helmets. I think it makes good sense. I can't remember who it was, but I recall someone reporting a concussion a year or two ago, after wiping out on a landing.

As someone who has broken their nose more times that I can count, has had their fair share of concussions (once so bad that I was bleeding from the ears, but the snot color was wild) and had most of my early teeth knocked out...  If you are concerned get a full face downhill biking helmet.  Much lighter (buoyancy) and they might make a vented version now (have not searched but the days of "helicopters" off cliffs on two planks are behind me, it hurts now).  Regardless of your choice, if you do pursue the full face 'vented'  helmet, test it out behind a PB with a bowling ball to see if it dives or not. The embarrassment you may feel sure beats the weeks of recovery if it does happen.