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Rivers

If you plan to cross a fallen log, take care to assess it's stability, slipperyness and the consequences if you fall off

Rivers are probably the greatest hazard you will encounter in the New Zealand outdoors. Drowning is so common here that it was once referred to as "The New Zealand Death".

"No one has ever starved to death by waiting in a hut for a flooded river to subside." Senior Constable Niall Shepherd, Arthur's Pass Search and Rescue.

River flow

New Zealand rivers tend to be steep and fast flowing, especially in mountain areas. Because the mountains do not store much of the high rainfall they receive, the river levels rise quickly after heavy rain. Because the rivers are steep and fast flowing though they also tend to go down again quickly after the rains stops. In extreme cases rivers can rise metres in a matter of minutes after heavy rain, but generally they rise over a period of an hour or two. Remember when crossing rivers that rain higher in the mountains can cause the river to flood even if it is not raining heavily in your area.

The two scenes below show the Crooked River rising after a few hours of heavy rain, and then back to normal flow again 24 hours later. In the photo on the left the main channel is only 3 metres wide, yet it is completely uncrossable.

Rivers rise fastest ...

When the rainfall is sudden and heavy
In steep, mountainous places
If there has already been rain recently (meaning that new rain runs straight into rivers rather than into the ground)
If the rain is falling on snow, causing the snow to melt

Deciding if it is safe to cross

This is the decision that is most likely to get you in trouble. The following rules of thumb are only guides. Don't cross if you have any doubt about the safety of a crossing, and always be prepared to retreat from a crossing attempt.

Don't cross a river ...

If the river is in flood
If the river is moving debris such as logs or boulders (the sound of a river rolling big rocks should be enough to scare anyone!)
If the water is so discoloured that you cannot see the bottom
If the water is flowing faster than you can walk. Throw in a stick and walk alongside it as it floats downstream to establish how fast the river is flowing
If the water is moving and more than mid thigh depth on the shortest member of your group. Throw in a large fist sized rock, if you don't hear it hit the rocks on the bottom with a clear "clack!', it is probably too deep (this is only an approximate method for estimating depth, take care!)
If there are hazard such as waterfalls, rapids, logs, large boulders, farm fences, weirs, trees, a larger river or a gorge (canyons) close downstream
If there is a bridge nearby, or other means of getting to the other side safely
If you feel uncomfortable about crossing

Choosing a place to cross

There are good places to cross rivers, and very bad places!

Choose a crossing ...

Where there is an easy entry point on your bank and an easy exit point on the far bank
Where the river is shallowest. Looks for wider parts of the river or where it splits into more than one channel. Rivers are usually deepest and fastest where they narrow, or on the outside of bends.
Where there is safe footing underwater. Avoid large boulders and logs and be wary of slippery algae.
That has a safe run-out. Look downstream, could you safely swim for at least 200 metres?

Crossing tips

For safe and happy river crossings...

Cross on a slight downstream angle. Do not try to fight the river
Take short steps, keep your feet a shoulder width apart
Take care, don't rush
Take off heavy clothing such as jackets (if prudent given the weather) and water proof or baggy trousers. They will drag in the current and also make it hard to swim should you fall
Water-proof your pack, line it with a plastic bag or some sort of dry liner, and twist off the top of the bag to seal it
Keep your boots ON! Wet feet won't kill you but loosing your footing and falling in could.
Keep your boots ON! Just in case you didn't get the idea. ON ON ON!
Ensure that you will be able to quickly undo your backpack if you fall in. Undo your chest/sternum strap but keep your waist belt snug to help with stability and to prevent your pack riding up over your head if you fall in. Practice quickly unclipping your waist belt (one handed) several times before crossing, and ensure it is not obstructed by your clothing. If you are not confident that you could quickly release your waist belt with one hand, or you have not practiced emergency swimming with a pack on, I strongly suggest leaving the waist belt undone.

Crossing techniques

The New Zealand Mountain Safety Council has developed a range of river crossing techniques that are widely used by kiwi trampers. These techniques have evolved over decades and are suited to our local conditions. Practice these techniques in safe places before you need to use them for real.

Alone

Use a pole on your up or downstream side as a support and face accross the current towards the other side. Hold the pole with both hands. If the current is strong lean harder on the pole. The ideal pole is stout and about your own height. If you have two trekking poles you can hold both of them together. Only move the pole or one foot at a time. If you need to retreat turn around (rotate downstream) and carefully move back to the shore. Crossing alone is substantially more dangerous than crossing in a group and should only be done with care in easier crossings (say below knee depth and flowing slower than walking pace, with a safe runout).

In a group

Link yourselves together by reaching through the gap between the back and backpack of your neighbours. Then grab a firm hold of their waist belt where it joins the bottom of their backpack on the side opposite you, as shown in the photograph. Position your strongest members at each end of the group. If a person loses their footing it is essential that everyone retains their hold on each other. Keep the group parallel with the river flow at all times. If you need to retreat, walk carefully backwards until you are in a safe depth then turn around. The use of ropes is inadvisable and has caused many drownings in the past.

1. Reach between the back and backpack of you neighbour and grab their waist belt on the opposite side...	3. Keep your line straight and parallel with the river flow
2. Pull you neighbours in close for support!	4. Take care and go slowly through deep or difficult water

Falling into a river

If you fall or are swept off your feet you need to react quickly and aggressively.

If you fall in...

If you are in a group hold on to each other and lean back onto your backpacks
If you are alone roll onto your back and face downstream
Keep your feet together and near the surface to avoid foot entrapment
Lean back to keep your pack down under you for floatation. If your pack pushes you underwater, undclip your waist belt and remove the pack
With your feet still facing downstream, point you shoulder towards the closest shore and 'ferry glide' towards it by backswimming with your arms (in a group only the people at the ends of your group can use their arms)
Don't try to stand up until you have bodily run aground in shallow, safe water. Take your upstream arm out of your pack straps and let the current swing the pack to your downstream side. In a group only one person should try to sand up at a time
Don't try to re-cross immediately. Work out what went wrong and consider again if it is safe to cross

Survival swimming
Swim with your feet downstream and close to the surface, leaning back hard against the bouyancy of your pack

Bridges, wires, cages and ropes

You are bound to come accross kiwi creativity at it's best (and sometimes worst) when you follow any popular or established track in a wet area... the diverse and delightful conbinations of cables and wire netting that constitute bridges in the back country.

State of the art technology...

Swing bridges (like wires and cages) are crossed 1 person at a time, walk steadily to avoid bouncing, and check that your pack straps are tucked away to avoid snags... don't drop your camera!
Wires come in 2 and 3 wire varieties. 3 wires have one cable for your feet and one for each hand, shuffle your feet sideways along the bottom cable, keeping the cable under the arch of each foot, while your body faces accross towards the far side of the river. 2 wires have one cable for your feet and one cable shared by both hands, and require you to face up or down stream. Lean forwards (if you lean backwards your pack will feel like it is trying to drag you down into the abyss) and shuffle you hands and feet along the cable.
Cages are a cage or enclosed frame that hangs below a cable suspended above the river. You climb into the cage with your pack, and use a winding wheel to move yourself to the other side. These can be very strenuous to operate, especially if you are alone (some have extra winders at each end so that others can help you). NEVER reach upward or grab onto the main cable or winding gears, as the wheels that the cage moves on can easily amputate your fingers or trap loose clothing or hair!
Ropes are generally frowned apon as an aid to river crossing. There have been several noteable drowings where trampers were using a rope to assist their crossing. With a rope there is a significant risk of entanglement, potentially trapping the victim in the river.