Water rescue: How to employ the tensioned diagonal system
The system is versatile, easy and fast to develop, and safe for swiftwater rescue of multiple victims
Scenario: You are dispatched to a stretch of river in your district that swells rapidly with rainfall.
The call states that multiple victims are trapped on a small island in the river. You know that the riverbed has multiple high points with trees and brush that become isolated “islands” when the water is up.
You arrive on scene and see four middle-aged men who decided today was the day to brave the rapids in their shiny new kayaks – but got in over their head. One of the men is still in his kayak against a strainer on the up-river point of the island. The other three are desperately trying to free him. The water is fast, turbulent and cold – and hypothermia will set in quickly if you don’t ask fast.
Ready, set, go!
When initial plans don’t cut it …
Too many times, these swiftwater rescue operations turn out less than desirably for local responders. Well-intentioned emergency services personnel rush into motorcraft or throwing operations without weighing all the options. For example, in many bodies of water, the current can quickly exceed the output of a motorized watercraft, resulting in boats that are not easy to control, not to mention additional victims in need of rescue. [Learn more about rescue equipment]
Throws should always be our initial focus, but throw bags cannot always reach the victims. Plus, if proper coaching techniques aren’t used, victims often let go of the throw bags before they can be secured.
So what else do we have to work with?
Learn the tensioned diagonal system
We are going to lay out a simple system that allows many variables to be applied to it, resulting in the rescue of multiple victims in a safe and quick manner. The system is referred to as a tensioned diagonal.
To paint a picture of the system, imagine a rope stretched tightly across a river. The rope is set at an angle to the current, meaning there is an up-river end and down-river end coming across the river at about a 45-degree angle to the current. Rescuers and victims can then “ride” the rope like a zip line, either in a boat attached to the rope or by holding onto “handles” connected to the rope while the rest of their body is in the water, allowing the current to push them down the line. The down-river end of the rope is a point of safety where additional rescuers are awaiting the victims and pull them out of the water onto land.
Deploying a tensioned diagonal
Let’s review a step-by-step approaching for deploying a tensioned diagonal:
- Step 1 – Get the rope across the river: This can be accomplished by throwing a messenger line across the river to awaiting crews. Once they receive this small cord, the near-side crews can tie a midline knot into the messenger line, and the far-side crews can pull the rope across the river. Other options include ferrying the line across with a boat. This can be done with paddling or with motorized operations. There are many details connected to doing this effectively, all covered in the accompanying video. In either case, the launch point for watercrafts will typically be up river from the objective in this scenario because the implication is that the current is very swift and potentially more than the watercraft can handle if needing to push up river.
- Step 2 – Anchor the rope: Once the rope is across the river, the far-side crew should anchor the rope to a tree or other suitable bomb-proof anchor. The strongest connection that can be made here would be a high-strength tie-off, also referred to as a tensionless wrap. This connection allows the full capacity of the rope to be available. This is important because the rope will be pre-tensioned at a critical angle, much like a high line. However, the water environment can be very challenging to operate in, and many times the available anchors are in the current. In these situations, faster connections, such as anchor slings or straps with carabiners and a figure 8 on a bight in the end of the rope, may be more appropriate.
- Step 3 – Tension the system: Once the rope is anchored on the far side, the near-side crew should have an anchor established with a multipurpose device and the elements for a 3:1 mechanical advantage, also referred to as a Z-drag. This would require a rope grab, either mechanical or a Prusik, a carabiner and a pulley. There are also more minimalist ways to rig a tensioning system onto this rope using simply knots and carabiners, but they require a more advanced knowledge base of ropes and knots. These would look very similar to a “trucker’s hitch,” which many firefighters are familiar with. When tensioning the system, one rescuer – and one rescuer only! – should pull on the 3:1. Additional tension can be applied by more advanced practitioners who are experienced in evaluating the forces applied to the rope. As a general rule of thumb, though, the one rescuer pulling will not allow the system to be over-tensioned.
- Step 4 – Evacuate the victims: Dealer’s choice! There are a wide range of options when it comes to evacuating the victims across the line and returning all crews and gear to the near side. Many of the options are decided upon based on victim presentation. For example, if the victims are physically fit, lucid, no medical challenges, and have donned proper PPE, they may be capable of holding onto their own connection and riding the line across independent of a rescuer. This is a high-risk choice and should only be made if many victims need to be evacuated quickly and there are limited rescuers. Additionally, down-river safety options should be in position before committing to this choice. This could mean additional throwers, down-river safety boats, and no monumental hazards directly down river. A safer option would be to have a rescuer hold onto a victim while the rescuer holds onto the handle and rides the line across. However, this option again requires the victim to be relatively capable in the water. If the victims are injured, incapacitated or simply not in the physical condition and PPE to make this style of journey, then the boat can be attached to the line and the victims can be loaded into the boat.
Key technical points
Let’s now cover some key technical points associated with the tensioned diagonal system.
First, establish the line so its height is approximately 3 to 4 feet above the water. The height is based on two things: 1) allowance for boat crews to pass under it if necessary and 2) handles that stay just above the water surface. Handles are constructed by simply placing a looped piece of software, such as webbing or a Prusik, into a carabiner and then clipping the carabiner onto the tensioned line. So, if you only have very short pieces of material, the line would have to be lowered slightly so that the handles would be within reach from the surface.
Second, when riding the line as rescuers or victims, assume a defensive swimming position – on your back with feet down river and toes up and out of the water. As you are looking down river, if you want to travel to the right side, you would create a ferry angle by pointing the back of your head toward the right and vice versa for river left.
When you are riding the line, you also want to create a ferry angle with your body to help your movement down the line. If the up-river anchor of the line is on river right, then you will be traveling down river to river left. To do this easily, make sure you grab your handle with your right hand and extend your arm. This will allow your body to travel perpendicular to the tensioned line and propel you to river left. The opposite is true if the line set were reversed. In this case, you would grab the handle with your left hand and extend that arm to travel to river right. This also allows your free hand to hold onto the victim’s PFD shoulder assembly or wrap around their armpit and chest.
The victim should be riding in a defensive swim posture as well between your legs. This allows you to drive your hips up to elevate them and wrap your legs around their waist for additional securing. More advanced techniques for rescue swimmers may include connecting leashes or tethers between the breakway attachments on the victim and rescuer PFDs.
Wrapping it up, safely
When the victims have been moved to safety, don’t shortcut your own safety by haphazardly blowing out the tensioned line and expecting the isolated rescuer(s) on the far side to make it back across on their own. The tensioned line can be slackened, and then relocated to the bow of the watercraft that took the rescuers across initially. Leave the tensioned line rigged into your multi-purpose device, and as the rescuers launch into the current to come back across the river, they can be rapidly pulled across by the rope.
A great resource
The tensioned diagonal system is great because of its versatility, ease and speed to develop, and safety. It can also be practiced on the bay floor at any time to develop rigging efficiency. There also many other uses for this line that we didn’t discuss in this article.
A little bit of gear, a little bit of knowledge, and a lot of practice and this can be a great resource for any fire department. If you haven’t built this or tried it before, give it a shot and let me know how it turns out.
Stay safe and train hard!
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