First Due: Slope Angles, Slope Profiles, and Evaluating the Need for Rope Systems

In this month's issue of First Due, we're taking the next step in rope rescue and talking about slope angles, slope profiles, and rope system decision making. Understanding slope profiles and angles and evaluating the need for rope systems is a critical knowledge base and skillset in rope rescue. This article should serve as either a valuable introduction or a refresher of knowledge you already have.

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Now, let's get on with the discussion!

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Whether responding to a vehicle accident, injured hiker, or structural collapse, first responders often encounter patients in sloped environments. Assessing the slope and determining how many rope systems are necessary is a key component of every rope rescue operation. Let's break down the main factors to consider when sizing up a sloped rescue scene.

Understanding Slope Angle

Slope angle impacts how much the ground itself can support rescuers and patients during movement. Slopes are often categorized into angle ranges:

• Flat: 0-15 degrees

• Low angle: 15-30 degrees

• Medium or steep angle: 30-45 degrees

• High angle: 45-60 degrees

• Vertical angle: Greater than 60 degrees to completely vertical

Focusing solely on degrees can be misleading though. A 30-degree slope may be easily walked if the surface is dry and solid. But that same slope could feel quite steep and precarious if it's covered in mud or loose gravel. Instead of measuring precise angles, focus on whether the slope allows rescuers to move freely under their own power without rope assist.

When the ground can no longer safely support rescuers and patients, either because of its angle or its surface conditions, it's time to break out the ropes. This often starts between 30-50 degrees but depends greatly on the surface terrain.

Evaluating Slope Surface and Runout

The composition of the slope surface and what lies below it are just as important as the angle. Loose, wet, or otherwise unstable surfaces like gravel, mud and snow require far more caution than solid, dry surfaces like concrete or dirt. Rescuers can easily lose their footing on unstable surfaces, increasing injury risk for both team members and patients.

Runout refers to what lies past the base of the slope. A hazardous cliff or water at the bottom raises the stakes of any fall or slip. In these types of conditions, ropes provide vital security even on a low angle slope. The right rope system acts as an anchor to prevent slides and falls. It also helps rescuers maintain control during patient movement.

Single Rope Systems

For low to medium-angle slopes with questionable surfaces, a single rope system may be sufficient to stabilize patient and rescuer movement. In this scenario, the rope acts as a safety or assist rather than bearing the full weight of rescuers and patients. Team members descend and ascend under their own power, relying on the rope for support in case they slip. A single rope helps stabilize movement on slopes where footing is treacherous but still possible. Additionally, a single rope mechanical advantage or descent control system may be useful in helping rescuers move a patient or victim up or down a slope, especially if personnel are limited or the victim is obese or of large stature.

Two Rope Systems

On high-angle slopes or those with treacherous footings and bad run-outs where a slip could result in a fatality or serious injury, rescuers and patients become completely dependent on ropes for security and/or mobility. Here, a two-rope technique is essential.

In the traditional model, one rope acts as the main line for lowering and raising litters while the second acts as a dedicated belay line, providing backup protection in case the main line fails. While this model may still be encountered, it's largely considered obsolete in the rescue world and "mirrored" or "twin-tension" systems are now the norm. In the mirrored or twin-tension model, both ropes have equivalent descent control or mechanical advantage systems in place and share the weight of the load as evenly as possible. This reduces the load for each system (including the anchors) and significantly reduces the potential for dangerous shock loading should one system fail.

In the vertical environment, on terrain too steep to ascend or descend without rope assistance, and in any environment where a rope failure could result in fatality or serious injury, the two-rope system becomes mandatory.

Decision Time

Looking for an easy-to-use tool to figure out one rope vs. two ropes? We like this simple algorithm from Rocco Rescue:

• Can rescuers move freely across the terrain without assistance and manage patient movement effectively and safely? Yes = no ropes

• Do rescuers need assistance to safely and/or more efficiently move themselves or the patient, but the ground is predominately supporting the load? Yes = 1 rope system

• Are rescuers and the patient fully supported by the system or a single rope failure would cause catastrophic results? Yes = 2 ropes.

Additional Considerations

Several other factors require evaluation when planning a sloped rescue:

• Litter teams: On low-angle slopes, up to 6 rescuers may directly carry a litter, but teams should reduce the number of attendants on steeper slopes for better rope control and maneuverability. In the vertical environment, attendants are generally limited to one to reduce the load on the system.

• Edge protection: Always pad sharp rock edges to avoid rope abrasion and damage.

• Communication: Coordinate verbally and visually during raise and lower operations.

• Equipment needs: Identify specialized gear you may need, like pickets, pulleys, and rope rescue hardware, before starting any rescue operations.

In rope rescue, the slope angle itself provides limited information. Carefully evaluating the overall slope profile, including surface stability and runout potential, yields a much clearer picture.

The Takeaway

So what's the key takeaway when sizing up a sloped rescue scene? Don't just measure the angle and reach for ropes. Take time to thoroughly assess the entire environment first. Determine how stable the surface is and whether the slope can be traversed without assistance. Identify any cliff or hazards at the base. Consider the patient's injuries and security needs. With a complete understanding of the slope profile, rescuers can decide if no rope, a single belay line, or a two rope system is the right choice to safely perform the rescue.

Want to learn more about angles, slope profiles, size-ups, and decision-making in the rope rescue environment? Join us for one of our 2024 courses, we'd love to see you there!