River Tracing Safety

Hypothermia

Hypothermia usually occurs due to prolonged exposure to cold water, especially when combined with lack of movement, and high caloric expenditure. Rivers with long gorges, deep pools without sun exposure, or located at altitude increase overall risk for hypothermia. 

Tips for keeping warm

In addition to bringing adequate clothing protection with you, a full rain suit can help mitigate the effects of evaporative cooling. Follow this link to the river tracing gear guide for more information on river tracing clothing.

Flash Floods

Flash floods occur when there is enough rainfall above a point in the river to quickly increase the volume of water flowing through that point. A large watershed and saturated ground due to previous rainfall are both factors that can increase the risk of a flash flood occurring.

During a flash flood there is a sudden increase in water volume (flow), and speed. Flash floods manifest as a wave of water traveling downstream. This wave can quickly increase the river height by 1 to 2 meters or more! In Taiwan, flash floods result in multiple rescues each year.

Tips for surviving flash floods

Flash floods are the most dangerous when you are unprepared for them. If it’s raining while you are river tracing, or if you suspect there may be inclement weather upstream of where you are, have a contingency plan in mind.

Make sure you are always aware of where you are in the river in respect to potential exits from the watercourse. As you move, keep an easy-to-reach escape route in mind. During heavy rain, avoid traveling through gorges and long pools.

In the case of a flash flood, you may have less than 10 seconds before the wave reaches you once you see it. Quickly move towards one side of the creek and climb up at least 1 to 2 meters above the current water level and higher if possible.

As long as you manage to climb up out of the water flow before it becomes unbearable, you can safety wait for the water levels to recede or for rescuers to arrive.

Falling Rocks

Features like canyons, gorges, and eroded sidewalls are extremely common in Taiwan’s rivers and creeks. The sides of creeks are often lined with debris and talus deposited from previous floods or landslides. It doesn’t take much for one of these rocks to start to slide down or fall outside. Rain, animals, earthquakes and teammates can all cause falling rocks.

Tips for avoiding falling debris

Always wear a helmet. If you see fallen rocks in an area, avoid it if possible. If travel through an area prone to rock fall is a must, move through it in a way that minimizes the chance of getting hit by a falling rock. One way would be to hug the wall below a cliff so that rocks have a greater chance of bouncing of the wall and away from you as they fall down.

Minor Injuries

Cuts and light bruises are relatively common. Wearing gloves, high-top river tracing boots and long sleeve river tracing clothing helps.

Always carry a first aid kit in a waterproof bag. Proactively sign up for training in wilderness first aid.

Taiwan’s Giant Hornets

It’s best to always back away from any nest encountered, and take the longest path around it that is possible.

In Taiwan, hornets build their nests in river valleys and on mountainsides between 0 and 2500 meters above sea level. They prefer to build their nests on boulders, on the sides of cliffs, on trees and in gorges. As a result, every river in Taiwan is likely to have a hornet nest in the vicinity or directly above the waterway.

The aggressiveness of hornets varies with species. The most territorial and most dangerous species is the smaller black-bellied hornet or Vespa basalis, which can fly at speeds over 8 meters per second (faster than you can run) and will chase trespassers for up to 100 meters. The black-bellied hornet becomes aggressive once trespassers pass within 5 meters of their nest.

Sources: https://tfc-taiwan.org.tw/articles/9688; https://news.pts.org.tw/article/555855

Rope Entanglement

There is always an entanglement risk when attached to a rope and in water. This risk increases with water flow and complex currents. If a person becomes entangled in a rope, their movement will be restricted and swimming will become more difficult. Even in a relatively shallow area, there is a danger of rope entanglement resulting in a drowning.

Read about an accident where rope entanglement was a crucial factor: Canyoning Accident Report: 2021/11/14 Qizhongtian Waterfall Group

Tip: If working with rope in water, always have an easily accessible water rescue knife and be trained in self-rescue. 

Low-head Dams & Recirculating Current

Low-head dams are among the most dangerous structures in rivers and have earned the ominous nickname “drowning machines”. The primary hazard of low-head dams is the powerful recirculating current they create at their base. The geometry of some waterfalls can also naturally create this same hazard.

Mechanism of Entrapment (The Boil Zone): In a recirculating current, there is an area known as the “boil zone” where highly aerated water results in reduced buoyancy. This area of water pulls objects back towards the dam or waterfall. Objects (or people) are forced down with the flow of the water, brought back to the surface inside the boil zone, and pulled back again. Without an external rescuer, this cycle repeats, creating a nearly inescapable trap.

Visibility: Visible; Massive structures that take up the entire watercourse

Escape difficulty: Even strong swimmers with life jackets struggle to break free. The aerated water reduces the effectiveness of swimming motions. The uniform nature of the dam often eliminates escape routes to the sides.

Strainers

A strainer is an obstacle in a river that allows water to pass through but traps larger objects, including people. They are often formed when fallen trees, branches, or man-made debris are brought into the flow due to erosion or floods.

Mechanism of Entrapment: Strainers can pin a person against the obstacle, holding them underwater with the force of the current. The combination of the force of the current and the physical barrier makes escape extremely difficult.

Visibility: Potentially visible; Located in or above the waterline

Escape Difficulty: Self-rescue is nearly impossible. The force of water pushing against the trapped person or object makes extraction challenging for rescuers as well. Rescuers must be careful not to become victims themselves when attempting a rescue.

Siphons

A siphon occurs when a part of the water in the river flows through a hole under rocks, boulders, or other obstacles in the river. These areas, which may be very difficult to identify, occur often in Taiwan’s rivers. Siphons are considered particularly dangerous due to their often hidden nature, high entrapment risk, and the extreme difficulty of escape or rescue.

Mechanism of Entrapment: A strong suction force pulls objects or people underwater and towards the opening of the siphon. These openings may be too narrow for people to pass through but powerful enough to trap a limb or an entire body at their entrance.

Visibility: Not easily identified!; Siphons can be particularly dangerous because they may not be obvious to river tracers. Unlike more visible hazards like waterfalls or large boulders, siphons can be hidden and appear in seemingly calm areas.

Escape Difficulty: Escaping from a siphon can be extremely challenging, often more so than from other hazards like hydraulics or eddies. The suction effect and confined space make any kind of rescue, even assisted, very difficult.

Undercuts

Undercuts are dangerous river features where water flows beneath a boulder, gorge wall, or other obstacle into a hidden underwater cavity. Often created where water is most forceful, such as the outside of bends, waterfalls, and high ledges.

Mechanism of Entrapment: Water flowing into the cavity will push objects into the undercut area, often at or below the water’s surface.

Visibility: Potentially visible; Can be spotted with careful observation

Escape Difficulty: Rescuing someone trapped in an undercut is extremely difficult and dangerous. If it’s an open undercut where water is pushed out and escapes in a linear direction, entrapment is less likely.

Further Reading

This article from Canyonmag on river hydrology and river hazards covers water flow in greater detail and delves into how to overcome the obstacles mentioned above while canyoning.