Many boaters start when they are young and fearless. In the old days, we paddled in fiberglass boats that put a premium on running rivers clean (not hitting rocks). We had an extra incentive to be cautious. Today's boats are somewhat indestructible. Hitting rocks doesn't crack the hull anymore. We even use rocks for certain moves. The learning curve has also been significantly reduced. Many boaters are paddling class III whitewater in their first year of boating, some are even paddling class V runs. The above changes in our sport leave little time to develop sound river judgment and experience to recognize dangerous situations. Training, practice, and patience when "Stepping Up" are the best way to avoid becoming a statistic. Fortunately we have learned a great deal over the years and have access to much better information sources and excellent formal training. You may find this article on judgment interesting as well as the contained links for further study: Judgment.
Floods are a special concern for river running. Besides the extreme power of water associated with flooding, there are many other hazards that might not be as obvious. Floods often topple trees along their river banks. These trees form death traps called strainers or sweepers. In large floods, large trees and boulders float downstream with the rest of the river. Trash like old refrigerators, cars, and barrels often get swept into the river - all of which can form nasty entrapment obstacles. Storm runoff in metropolitan areas include sediment, oil, fertilizer, and herbicides. Overtaxed sewage treatment facilities often overflow in floods as well. Why bother paddling streams in severe flood stage when you can finally catch smaller streams that seldom run.