[Blaze]

How You Loose Body Heat
The water environment of the paddler greatly increases the potential the potential for heat losses through evaporation and convection. Layering your clothes combines the best properties of each garment to reduce heat loss. A sweater reduces convectional losses by creating dead air spaces in the fabric. A paddling jacket reduces air flow and reflects radiated heat losses from the body back toward the body. The summer paddler also needs to protect himself by wearing a hat to reflect the sun's radiation. Also, a cotton shirt and shorts help cool the body by evaporation.
Conduction (e.g. hand on aluminum shaft of paddle)
Convection (e.g. wind)
Radiation (e.g. unprotected head)
Evaporation (e.g. wet lifejacket and wet clothing)
Common River Hazards

Foot entrapment - Catching a foot in rocks on the bottom of the river. May be caused by trying to stand up while getting swept downstream in water mid-thigh to mid-torso deep.
Strainers - Trees or single branches in the current, with river water flowing through, can cause a severe pinning hazard. Strainers many be caused by erosion. Trees can also fall because of old age, floods, and storms. Look for them on wooded riverbanks, along small creeks after high water, often found on the outside of bend, and on less utilized rivers. Always look downstream to spot bobbing twigs or irregular flow patterns.
Man Made Entrapments - Manmade objects in the river are inherently more dangerous than most things natural. Keep an eye out for bridge pilings, low head dams, junked cars, any man made object found commonly in urban riverways, highway crossings, and abandonned dam sites. Make it a habit to visually scan downstream.
Broaches - Getting pinned on a rock, either amidship or at the ends. Avoid sharp rocks that can potentially crease a boat or serve as point to be wrapped by your kayak! Develop the instinct to lean into the rock with your boat and body leaning together.
Undercut Rocks - Undercuts are water features where a slab of rock, or rock shape, forces the current flow to go under the surface. Learn to spot them by the dark shadow on the upstream side of the rock, the lack of pillowing action by oncoming water, and by the lack of a predictable eddy on the downstream side. Most dangerous undercuts are well known by locals, and listed in guidebooks.
Entanglement - Getting tangled exiting your boat is most likely to be caused by ropes, and loose lines, in your boat. Practice wet exits and critically evaluate your outfitting for entanglement potential. Treat throw ropes as potential hazards. Keep them neatly bagged, and carry a knife for rescue.
Vertical Pins - When the bow buries and gets pinned on the bottom after a steep drop. This is not a concern until you are paddling drops of over 3 or 4 feet. Advanced paddlers prevent them by checking the water depth first, and leaning back and performing a 'boof' move to keep the bow up. Paddling boats with a large volume bow reduces this risk substantially.
Hydraulics - have evenly formed backwash, water moving back upstream for four or more feet. Holes with more of a wave shape are intimidating, but typically less hazardous than water flowing smoothly upstream. Dams, and hydraulics that are very regular, and perpendicular to the current are far more dangerous than hydraulics angled with one end downstream.
Long Swims - Wearing a tight PFD, matching your ability to an appropriate river, and being dressed for a swim can be excellent defense against a long swim. Another great precaution is a competent group of friends with either a shore or boat based rescue plan.
Recognizing and Avoiding Hazardous River Conditions

Conditions on rivers can change rapidly in Texas. Before setting out, a paddler should know the flow condition of the reach they are about to paddle. During high flows, the whole river reach may act like one long set of rapids. During high flows, the fast current may draw the unsuspecting paddler into other hazards. These include entrapment in floating debris such as logs, sweepers and strainers.
A sweeper is an overhanging branch or tree whose branches extend into moving water from above. Running into a sweeper will push a canoe over or could push and hold the paddler below the surface of the water. A strainer is a submerged tree or branches under the surface of moving water. A paddler could become pinned against a strainer.
Submerged hazards, such as rocks, logs and other debris, are not easily seen in turbulent water. A collision can cause the boat to upset; the hull may be punctured, or the paddler may be injured in the collision.
Once out of the canoe, the canoeist may be overcome by the current or pinned by the canoe. A swamped canoe can weigh as much as two tons and a paddler can be crushed between a canoe and a rock.
Cold water (less that 15° C) can be lethal. During spring conditions or in late fall, the river water is cold, and if you spill you can very quickly be overcome with hypothermia. Even if the paddler reaches shore, wind chill and cold air temperatures can accelerate the dangerous drop in body temperature. Shivering is an indication of the onset of hypothermia, and victims usually become too disoriented to be responsible for their own safety.
A riverbank is often well removed from emergency services and homes where help can be obtained. The tough reality is that you may be on your own to deal with a life-threatening situation. The tough reality too is that a paddler in danger may also be putting a rescuer's life in jeopardy.
Whenever you are on the river, it is important that you are prepared to deal with an emergency. Know where access points are along the reach of river that you are canoeing. Have a map of the reach that you are canoeing. Have a first aid kit and know basic first aid. Finally, a cellular phone in a waterproof bag may be invaluable in contacting help or emergency services.
Low head dams pose a special hazard to paddlers. In the fast waters, an upstream paddler may get too close to the crest of the dam and be swept over. A paddler may also get caught in the backwash current at the downstream side of the dam. Once in the backwash current, the paddler becomes trapped. Paddlers should use portages around these structures, and stay well clear of low head dams at any time of the year.
Boating safety awareness is not limited to the cold-water seasons. There are good solid rules that must be observed by prudent and safety conscious paddlers everywhere. Boating courses are an enjoyable way to prepare for any kind of boating.
Like the Boy Scouts advocate-be prepared. Being prepared before your trip can help avoid potential hazards or result in a positive outcome if an accident does occur. One of the most important considerations is a trip or float plan. Let someone know where you are canoeing, what your boat looks like and when you expect to return.