In reply to UKC News: I'm sorry to hear about an accident leading to a death, it is understandable as whitewater can look safe even when it is very dangerous, and dangerous when it is safe. In this respect a four foot drop can be more dangerous than a hundred foot waterfall, dependant on the water features.
The danger is caused by the water recirculating at the base of a waterfall or weir, and the most innocuous looking drops can contain potentially lethal towbacks, this is because the water flows upstream immediately below the drop so you get stuck inbetween water flowing downstream and water flowing upstream.
People may be aware of this, however unless you are a kayaker you have very little reason to study the exact nature of these formations and they can be easily misjudged. I do not know if this caused either of these incidents however it is worth noting.