I would imagine the side arches are pretty clogged too, I have to admit I can't remember what the bridge looks like now as I never go up that way anymore (I'm never going to get 8'8" under at anytime, ever), most bridges in a flowing river have a bit of height difference if they restrict the flow in anyway.
Haven is pretty impressive for it's level change in a good flow, often with a standing wave underneath which is pretty nerve wracking when you are bit close on clearance.