from George Sayour, Paddling Guide About.com

Kayaking During Flooding: Debris in the Water During Flooding
Flooding is nature’s way of cleaning out the environment. Everything that is on land near a river or other body of water gets washed into the water. Included in this list is branches, logs, full trees, and even old tires. This effect is usually the greatest in the first 24 hours after a major storm. The effect this has on the paddler in the most immediate sense is due to the collision that could happen between the kayaker and the debris. This is especially significant for those boaters who are taking advantage of surfing the waves and playing in holes that the flooding creates. It is best to have a spotter, someone watching up stream, while another boater is playing in the waves. So, the bottom line here is to be alert and watch out for 40 feet trees knocking you out of your newly discovered surf wave that is a result of the flooding.

Kayaking During Flooding: Changed Water Conditions During Flooding
This sounds like a no-brainer, as any different water level changes the characteristics of the river. But flooding can permanently change a river. The high volume of water often moves rocks, washes new boulders into the river, and causes obstructions where none previously existed. This of course will change where waves, holes, and eddies are. So, just because you’ve paddled a river at the current level before, the flooding could have actually changed the landscape of the river thereby creating obstacles you weren’t ready for. Treat your journey down the flood-stage river as your first, as in many ways it will be.

Kayaking During Flooding: Strainers and Blockages During Flooding
Strainers are one of the most significant dangers whitewater kayakers and canoeists will come across while paddling a flood stage river. As debris washes into the rivers it often collects along turns, against boulders, in holes, and against overhanging trees on the river banks. This not only causes an obstruction, it also causes the current to increase and even change direction as the river attempts to navigate through and around the obstructions. These strainers have caused many whitewater kayaking and canoeing mishaps and have even claimed lives. Once stuck in a strainer, the only way out is to climb up on top of it. Paddlers need to proactively avoid strainers as far away from them as possible since the current will often suck paddlers who were clear of these deathtraps right into them. Furthermore, in the case of debris caught in holes, the paddler may not even know they are in there. This means if a paddler can’t see what is past a horizon line, they need to get out and scout or approach with extreme caution.

Kayaking During Flooding: Rising Waters During Flooding
It is to be expected that the water will rise as a result of severe rains. What is under discussion here is when the water actually rises during a paddling trip. This noticeable difference generally occurs on small creeks and slot type canyons where water washes down the mountain and pours into the rivers. It can be an eerie feeling to enter the river at one water level and notice it changing and growing with time. This intensifies all of the other watch outs this article has been mentioning. Furthermore, it is quite possible to begin a flood stage kayak trip at a manageable level and the river growing to an un-doable level in no time at all. The whitewater paddler must therefore have an evacuation plan any time they are canoeing or kayaking during flooding.

Kayaking During Flooding: Stronger Currents
This is another one of those no-brainers, but as the saying goes common sense is the least common of all the senses. The higher volume of water, rapidly rising characteristic of the river, and increased obstructions that flooding brings causes the currents to become very strong. In practical terms, this means the whitewater paddler must be more deliberate in getting from place to place on the river. Whereas you usually wait to pass a certain landmark to get to the middle or left of the river, you’d better a lot more time to do so.

Kayaking While Flooding: Conclusion
The gist of all of this is that while whitewater paddling during flooding can be a blast, safety must come first. While shortcuts and lax safety should never happen on the river, it goes doubly so when there is flooding. Good scouting techniques should be employed and the group must watch out for each other. When approached safely, whitewater kayaking, canoeing, and rafting during flood-stage conditions is a true gem of an outdoor experience.