Guide To Classification Of Rapids


A boat racer careening around a rapid is nothing short of breathtaking! It is a high definitive moment like that of a gladiator facing a challenger, which is not only energy bubbling but gruesomely mysterious. From white water kayaking, team-racing, and canoe cruises, to yoga on the paddle, the magic of finding the unknown truly did not end with Vasco da Gama!

Precisely, because rapids are energy-filled mysteries, as they may contain dangerous hazards ahead, behind, or around them. These hazards reduce speed and change course and therefore need proper moves to negotiate through them.

What is a Rapid?

A rapid is a section on a water body where the water surface becomes shallower and therefore exposes the rocks or obstacles beneath, causing the flowing water to splash over the obstacles. As such, water flowing through a rapid appears white and has an unstable current. And being less buoyant it is often avoided by boaters because the nature of the obstacles is uncertain.

Still, the energetic waves created by these natural wonders of the water world instill an imbalance in any water machine. Hence, their guides have to develop the necessary momentum to steer them ahead.

Rapids develop spontaneously during floods and high rainfall seasons due to the movement of obstacles from one point to another. They are, therefore, impossible to eradicate unless blasting is done. While blasting may not be needed in some cases, if you are planning for a recreational trip, scouting before touring could be important, as it could help you know the nature and number of rapids before travel.

How Are Rapids Classified?


Rapids change over time depending on the steepness of the river surface, the width of the water surface, the number and size of obstacles of the river, and the speed of the water flow. An attempt at rapids classification in fixed grades, therefore, is not possible because they will vary with water depth and speed of flow.

Rapids, therefore, are classified according to:

  • The height of the drop
  • Maneuvering or negotiating skills required by the paddler or boater
  • Presence, absence, or volume of whitewater
  • Presence or absence of waves and
  • Nature of hazards

If you are expecting to spend a week or a few on a recreation tour, a guide to rapid classification may come in handy and keep you safe on the go. Whether you are going on a rescue mission, for underwater photography, a racing championship, or just fishing down the white water, this rapids classification guide will help you know what to expect.

Major classifications of Rapids

According to the International Scale of River Difficulty, rapids can be divided into the following six categories:

1. Class I rapids

These are rapids with a small rough area of white water or slow-moving water and are fit for gentler recreation like yoga. The boater may require little maneuvering skills or none because there are few or no water hazards. However, maneuvering skills can help a beginner to navigate the white waters like a pro.

2. Class II rapids

Class II rapids are rapids with some rough water, few rocks, and a few waves. Here, the water moves faster than in class I rapids and therefore, a boater may require some maneuvering skills during the navigation. However, paddling through the hazards and obstacles is relatively easy and can even be done on a canoe.

3. Class III rapids

This category includes rapids with small waves, which are generated by obstacles. Waves are noted by a random and rough pattern on the surface of the water. Since these ripples are rarely perpendicular to the flow of the river, they can capsize or flip over the boat quite easily especially if they are flowing sideways. But with the proper gear, boarding can still be fun.

Class III rapids are also known for small drops about 1-2 meters in height. Again, the selection of the right gear and proper techniques will ensure you have a smooth flow to significantly maneuver through these rapids.

4. Class IV rapids

Class IV rapids have medium waves, some rocks, and sizeable drops, which require severe maneuvering. These rapids are characterized by plenty of white water, and therefore boats sink easily because white water has less buoyancy than normal water.

5. Class V rapids

These fall under the classification of a rapid that has plenty of rocks, large waves, and huge volumes of white water. A class V rapid is likely to have large rocks and hazards such as fallen trees, broken concrete, or even wire fence, and therefore large drops are expected. This means that a boater requires precise moves at specific points to avoid danger. Only experts or people with good mastery of paddling can be able to cruise over these rapids.

6. Class VI rapids

Class VI rapids have huge waves, rocks, and hazards with drops that can destroy boats and equipment. Although full mastery of skills is required to navigate, paddling through such rapids is extremely dangerous and often leads to injuries and sometimes death. Before attempting these rapids, it is imperative to run a thorough check on the water conditions and levels to ascertain safe boating.

Class VI rapids have many hazards that can be very dangerous and risky to navigate. Such hazards may include some of the following:


A hydraulic is a feature where, as water flows over a submerged obstacle it flows back upstream at a right angle, creating a whirling current more like a vertical eddy known as a hole. This poses a hazard to oncoming boaters. Though such holes create a splendid area for playboating display, the current might be strong enough to discourage paddling through. Such boaters may find themselves at the risk of being whirled around the hole by the current, leading to injury.


Eddies are currents that are formed by waves generated behind obstructions. Insignificant drops like those found in class VI rapids, eddies may develop into a strong whirlpool which may be impossible to pass through but normally are a calm and fine place for resting before proceeding.

Eddies and holes rescue missions are not uncommon. However, one needs to plan properly before packing for such trips. This could include deciding to a diver onboard or learning scuba diving.

Planning could also include shoving some basic gears like a wet suit, dry suit, nose clips, helmet, and buoyancy aids for a fun-filled and safe trip. You can have these accessories in pairs to ensure a better rescue-mission. Enough floatation materials might also come hardy in cases where one is caught in never-ending whirlpools and swirling water, or where one is trapped beneath undercut rocks by the current.

Eddy walls

Just as the name suggests, these are walls flanking an eddy on both or one side due to the height of the river being higher than the level of the water on the eddy side. Such walls prevent a boater from paddling back into the water.

Wide dams

These are low set obstacles that create a dam situation. For example, fallen trees and piled logs may form wide and uniform barriers, which could be hard to paddle around.


These are large outstanding obstacles, which cause water to flow backward hindering forward movement. Pillows are so named because they form a pillow-like hump above the obstacle as water flow through.

Huge waves

Huge waves can crash boats onto rocks, destroy equipment or injure the owner. It is, therefore, necessary to select a water machine that can dodge through large waves with ease.

Undercut rocks

A rock may be worn down below the surface of the water, thus trapping a boater underneath it. Eddies formed below such a rock can flip a boat leading to disastrous episodes.

Strainers and sieves

Strainers are large obstacles that let water pass through but block the passage of the channel. Sieves, on the other hand, are lesser obstacles that may pin (wedge between rocks) the boats and push them into a thin section, where they might be impossible to retrieve. Such obstacles may be piles of broken concrete, tree roots, or leaning tree branches. These can structurally damage the boat or equipment, or cause actual bodily harm.

Back to Class V

Once a class VI rapid has been navigated, it is classified under Class V if the navigation was successful. Excellent paddlers have gained skills to dodge most of these obstacles and might be able to beat the current and sail through.

But we mentioned earlier that rapids change with time. An increase or decrease in the flow can create a rapid, wash away a rapid, or make a safe passage through. Therefore, categorizing a Class VI under Class V requires specifying the point of navigation and season of the year when navigation was successful.

Globo Surf Overview

The above rapids classification can guide you when planning for a fun-filled cruise. Maybe you are planning to go down the white waters with a canoe, catamaran, kayak, or raft. Perhaps you are eyeing on a more adrenaline-rushing activity like squire boating, playboating, or slaloms on the freestyle. Knowing what awaits on the other side helps you prepare effectively and get the appropriate equipment for the activity.

Classes I, II, III, and IV rapids pose less threat for water borders but class V is only to be navigated by skillful navigators. Class VI rapids, on the other hand, should probably be avoided since they pose a threat to life.

When making such decisions as to which equipment to buy, the skill set needed, or best fjords and creeks to go fishing, a guide to rapids classification could be a good point, to begin with. Depending on the skills required, watersports gaming in risk-taking endeavors is a great way of developing teamwork, strength, endurance, and fitness.  However, one needs to prepare thoroughly and take the right precautions to minimize chances for accidents.

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My name is David Hamburg. I am an avid water sports fan who enjoys paddle boarding, surfing, scuba diving, and kite surfing. Anything with a board or chance I can get in the water I love! I am such a big fan I decided to start this website to review all my favorite products and some others. Hope you enjoy!