Considerations in Swift Water Rescue
A swift water rescue is a form of rescue centered on fast-moving conditions that involve water more than two feet high and with a flow rate of at least one knot (1.15 miles/hour). While often referred to as white water rescue, this rescue is not limited to rapid rivers. It applies to flooding events involving flood control channels and drainage environments not usually submerged. The buildup of outflowing water downhill in a relatively confined area creates a potentially catastrophic condition for property damage and loss of life (when water flows at a speed of less than a knot, the operation is known as surface water rescue).
Any swift water rescue activity, by definition, entails extreme risk. For this reason, risk/benefit analysis is an integral part of any such operation. In addition to victims' risks, such evaluations consider the hazards rescuers face. An objective assessment of equipment and capabilities, as well as likelihood of success, is imperative. For communities, this involves risk assessments long before incidents occur. Flood vulnerabilities should be checked annually, with responders pinpointing access points along natural drainages and manmade channels and spots where entrance and egress may be extremely limited or impossible.
When emergencies occur, technologies such as drones, satellites, and tablets enable aerial views that pinpoint the specific locations of victims and the hazards and threats they face. In addition, responders undertake on-scene visual size-ups that involve scanning the landscape and identifying current strength and direction relative to victims. Armed with a knowledge of hydrology and water conditions, responders make rapid decisions on whether and how to proceed.
The common elements assessed are waves or flow impacted by constrictions or obstacles. Humps are waves that often indicate an obstacle under the water's surface, while holes are waves that break back upstream as a result of such objects. Haystack, or standing waves, are stationary waves within a channel. A boulder sieve is a collection of boulders within a channel that functions as a filter, letting water, but not solid objects, pass through. A frowning hole indicates an area of strong reversal of water flow, running side to side. This may provide an opportunity for exit under the surface. The current vector is the strongest main flow within a channel and is often, though not always, parallel to the shoreline.
These and other factors help determine which approach responders take from available access points. In many cases, the speed of the swift water exceeds that of motorized watercraft, such as boats and rafts, making them hard to steer and control. In addition, narrow channels could obstruct or overturn the craft, creating more victims needing rescue.
An alternative approach involves using a throw bag or a bag containing a loosely stuffed rope (usually 35 to 50 feet long) that pays out through the top as it travels downstream in the victim’s direction. With these, the rescuer takes a position on the upstream side of the rope and dips the bag in water, making it heavier and increasing the throwing distance.
The throw is either side or underhand, with the latter involving a backward swing, a sharp forward swing, and release at eye level. At the same time, the rescuer shouts “rope,” with the victim wrapping the rope around their arm several times and then laying on their back and floating their feet up, kicking as pull tension is applied. In many cases, the rescuer's weight is the anchor, with their dug-in weight and pulling power bringing the victim to safety. In other cases, they anchor the rope to a tree or other stationary structure near the bank.
Another approach is deploying a tensioned rope across the waterway to crews on the other side. The rope is often thrown using a small corded messenger line, which is knotted to the heavier rope and used to pull it across the channel. Alternatively, the rope can be ferried across the waterway by vessel. The rope is typically anchored to a strong tree or other structure on both sides and tensioned appropriately. This allows victims to use the rope to guide and support safely crossing a flooded area.
