Go with the flow and make your swift water rescue operations safer
During any given year, floods kill more people than any other natural disaster in the United States. First responders often face the grim scenario of someone trapped on a stationary object amid the floodwaters, or worse, adrift in the rushing torrent. Few places exist where flooding is not an issue, and few situations are more challenging or more dangerous.
Flood-rescue incidents are, by nature, some of the fastest changing and most demanding rescue situations. As such, first responders and rescue team members always run the risk of plunging into the fast-moving water (either by accident or by design) and becoming engaged in a life or death struggle for survival with the force of the current and the many hazards that exist in the water. Swift water rescue and swift water rescue training are both dangerous and demanding and solid procedures are vital for your success.
There are three main characteristics of swift water. First, it’s powerful. Water weighs 62 lbs. per cubic foot (cf ), and when those cubic feet move, they exert tremendous force. For example, the water moving through just one turbine in Arizona’s Glen Canyon Dam produces more than 155,000 horsepower. Second, swift water is relentless. Waves in the ocean come and go, but if you get pinned against an obstacle or strainer in a river, the relentless crushing force of the water won’t dissipate. Even the strongest men are no match for the force of a rushing river. Third, swift water is predictable. This is the most important characteristic to the rescuer. With swift water rescue training and experience, you can predict with certainty where both safety points and danger points are located on a river. When it comes to hydrology, there’s little difference between the Snake River, the Colorado River and your local waterway. Water behaves the same way when it moves over and around objects, no matter where they are. This knowledge is the rescuer’s greatest asset.
Many people don’t realize just how many hazards exist in swift water. Even rivers that appear calm can hide serious, life-threatening dangers. If you’re a swimmer, boater or rescuer, you should become familiar with the hazards listed below. (For information on how many flood/river fatalities occur each year, visit www.nws.noaa.gov/om/hazstats.shtml.)
The hazard that kills the most people on rivers each year is known as a strainer. Any object in a river that allows water to pass through but traps a person is a strainer, the most common of which is a tree or log out in the current. Other objects, such as fences and even vehicles, can pose significant strainer hazards as well. Flooding causes rivers to swell far beyond their banks, often into trees and fences that line the channel, which creates strainers. Anyone in the water must recognize strainers and avoid them if possible— or climb over them in a sheer act of survival. If you become pinned on a strainer or even worse, go under one, you’ll most likely die.
Water conducts heat about 25 times faster than air of the same temperature.
Several hypothermia studies have concluded that a person without adequate thermal protection in cold water will quickly become incapacitated. In 40- degree water, an unprotected rescuer has about seven minutes to perform useful work. Mild hypothermia occurs when the body’s temperature drops to between 96 degrees and 90 degrees. Symptoms include marked shivering, decreased coordination and manual dexterity and mild confusion. Moderate hypothermia occurs when the body’s core temperature falls below 90 degrees. Symptoms include cessation of shivering, dilated pupils, bradycardia, a marked decrease in mental function and decreased respiration. Severe hypothermia occurs when the body’s core temperature drops below 82 degrees. Symptoms of severe hypothermia include coma, significant hypotension, respiratory arrest and cardiac dysrythmias. Thermal protection is a must for survival.
A hydraulic is a vertical reversal of water. Any time water flows over an object, such as a rock or a slab of concrete, it creates a reversal of flow much like an eddy. But unlike an eddy, hydraulics aren’t friendly places. A strong hydraulic creates a churning, recycling motion that pulls a swimmer under water. As the swimmer resurfaces, the hydraulic pulls them back down under water.
Hydraulics are also referred to as Maytag holes, suck holes and keepers.
A low head dam creates a dangerous river-wide hydraulic from which there is no standard escape route (other than the bottom swim). Low head dams are typically concrete structures placed across a waterway by agencies like the Army Corps of Engineers in order to slow stream flow and prevent channel erosion. However, anything that crosses the entire channel (like a roadbed or a concrete utility duct) can form a river-wide hydraulic like a low head dam. All but the most experienced and luckiest of swimmers will violently spin and drown in this common river feature; low head dams are often called drowning machines. Swimmers can spot a potential low head dam by a looking for a telltale horizon line on the river. That is, the river just seems to end, and you hear a rumble and a roar. The horizon line is your cue to swim for your life and get out, eddy or not.
Rescuer must be aware of these hazards and understand the swift water rescue training is vital for safe effective swift water rescue operations. The Essential Technical Rescue Field Operations Guide is the best resource you can get to assist you in your swift water rescue program.