New Zealand Rafting Safety

How Does Rapid Grading Work?

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Class rapids system, how are rapids graded internationally 2018-05-23T03:11:35+00:00

How Does Rapid Grading Work?

Classification of Rapids

The following classification is based on the international white water rafting rapid grading system. River rapid grades are approximate rather than definitive measures of a rapid’s seriousness or difficulty.

The difficulty and seriousness of any section of river can alter dramatically within a short space of time through factors such as increased or decreased flow, new obstacles and changes in river bed topography.

Something further to take into account is that higher grade rapids sometimes have consequences associated with not getting “it” right.

This may include a very short recovery time to right a flip, or an unpleasant swim scenario.

A further point to note is that extreme kayakers have over the last few years pushed the boundaries of what was once considered runnable. This has lead to a redefinition of some rapids with the addition of plus or minus symbols being attached to the main grading.

This further split of the classifications is really subjective, and should not detract from the overall classifications set out below.

Grade 1

Rapids are small regular waves. The passage is clear and easy to recognise and negotiate. Care may be needed with obstacles like fallen trees and bridge piers.

Grade 2

Rapids have regular medium sized waves (less than 1 metre), low ledges or drops, easy eddies and gradual bends. The passage is easy to recognise and is generally unobstructed although there may be rocks in the main current, overhanging branches or log jams.

The following River Valley Rafting trips are primarily in this grade;

Scenic Fun
Lodge to Lodge Rafting Trip
Fantail Canyon Overnight Rafting Trip
Mokai Canyon Three day Rafting Trip
Rangitikei River Explorer

Grade 3

Rapids with fairly high waves (1-2 metres), broken water, stoppers and strong eddies, exposed rocks and small falls. The passage may be difficult to recognise from the river and manoeuvring to negotiate the rapid is required.

The following River Valley Rafting trips are primarily in this grade;

Rangitikei River Headwaters Expedition
Mountains to Vineyard – Overnight on the Ngaruroro River

Grade 4

Difficult rapids with high, powerful, irregular waves, broken water, often boiling eddies, strong stoppers, ledges, drops and dangerous exposed rocks. The passage is often difficult to recognise and precise and sequential manoeuvering is required.

Grade 5

Very powerful rapids with very confused and broken water, large drops, violent and fast currents, abrupt turns, difficult powerful stoppers and fast boiling eddies; with numerous obstacles in the main current. Complex, precise and powerful sequential manoeuvring is required. A definite risk to personal safety exists.

The following River Valley Rafting trip has rapids that fit within this grade;

Grade 5 White Water Rafting

Grade 6

All previous difficulties increased to the limit of practicability. Very confused and violent water so difficult that controlled navigation by raft is virtually impossible. Significantly life threatening if swimming and unrunnable by all but a few experts.

What Boats Do River Valley Use?

Mohaka White Water Inflatable Kayak

Surprisingly strong and very stable, the Mohaka will handle big waves and survive impacts which would break rigid hulled kayaks. It is self bailing which makes it practical as an open boat in big rapids, and it has good carry-through in holes and stoppers. The long waterline and the smooth underside profile contribute to the Mohaka’s snappy performance with its low drag, its high speed, its ease of turn, and its ability to ferry glide in marginal conditions.

A raft that works equally well as an oar rig or paddle boat and is used commercially in many parts of the world. The W38 rewards us with snappy performance and easy paddling or rowing – it is fast, easy turning and stable in extreme conditions. River Valley use it extensively on a number of trips, including, Grade 5 at summer flows, Rangitikei Headwaters Expeditions, various Grade 2 sections.

3.8m (12'6") W38 Motu Self Bailing Raft
4.6m (15') W46SX Rangitikei Self Bailing Raft

A good looking and very popular raft, with its square-back design and self-bailing floor which are features developed for New Zealand outfitters running day trips on Class V rocky technical rivers. River Valley run this raft with both paddle and oar configurations depending on the section being rafted, and the clientele.

River Valley operate a number of cataraft models. These versatile, and high performance boats are used primarily as safety boats, or photgrapher craft.