Rivers

More people drown in rivers than in any other New Zealand water environment. 

Rivers can be dangerous depending on the weather, terraine, forces, hazards and behaviour of those recreating in and near rivers. Rivers generally are not patrolled and the absence of warning signage and ignorance of the dangers a likely contributor to injury or death by drowning.

Rivers present a completely different range of potential dangers compared to the ocean and swimming pools. The pressure of moving water is constant and can be powerful even if the river looks slow moving and calm.

Safety and Hydrology

Water in rivers exerts a very powerful force against any fixed object. This force remains constant unlike the ocean where the force is released with each tidal surge.

The downstream flow of water is called laminar flow. Water flows in a straight line, changing direction at points of high resistance. The line of greatest depth and strongest laminar flow will be on the outside of the corners. The water on the inside of the bend is slower moving. 

Within New Zealand there is a recognised grading system for rivers. This classification is based upon difficulty, loss of height, amount and speed of water, and the number of hazards. Grade 1 is the easiest, Grade 6 is the hardest.

River crossings

Most river crossings are conducted safely and successfully, however unfortunately not all crossings go so well. 

When attempting a river crossing, these three crucial decisions will help you to reduce the risk:

1. Should you cross?

Crossing alone is hazardous and it is not recommended that you get yourself into a river crossing situation if you are alone.

2. Where should you cross?

  • Never cross a river in flood – 80% of river crossing drownings have occurred when the river has been in flood.
  • Check the speed of the river, look downstream for run out hazards and see if there are good entry and exit points
  • Avoid crossing on a bend, above a place where another stream joins the river and where the water is dirty and cloudy.

3. How should you cross?

  • Check your clothing and equipment.
  • Avoid loose bulky clothes.
  • Wear your boots or shoes.
  • Try to keep the gear you are carrying in your pack/day pack dry. Make sure that it is all in plastic bags.

When crossing always:

  • keep your body side on to the current;
  • take small shuffling steps;
  • move diagonally downstream with the current to conserve your energy;
  • have a leader to control the crossing make sure that everyone can hear instructions before you get into the river;
  • have the strongest people at the upstream end to break the flow for the others;
  • have the upstream person just slightly ahead of the person next downstream and so on down the line. 

If the crossing does not go as planned:

Stay linked up and back up slowly out of the river. Do not break the link until everyone is into very shallow water.

Swimming

Swimming spots in rivers can be great places in summer. If you pick your spot carefully and check it out each time you swim there you can keep yourself and your friends safe.

Swimming in a river is different from swimming in a pool or in the sea. Swimmers often underestimate the power of the river or overestimate their own abilities.

The river bottom is irregular and can change from day to day. It is often difficult to tell how deep a certain part of the river is. Many people are seriously injured each year jumping into water that is too shallow.

Stay safe when swimming in rivers by:

  • Learn swimming and swimming survival skills.
  • Always swim as part of a group.
  • Check for hazards both where you are swimming and downstream.
  • Do not mix swimming with alcohol or drugs.

Check out any jumping spot thoroughly before jumping. Do this by getting in the water and physically checking the depth and the whole landing area. Do this every time you visit a jumping spot to check that nothing has drifted into the landing zone since you were last there.

Floods

A significant danger occurs when our rivers, creeks and streams flood. Debris and fast flowing currents can cause banks to become unstable and even a small rise in the water level can dramatically change the way a river flows.

When inland waterways are in flood it is important to keep out of the water wherever possible and keep well away from river and creek banks, they can become weak and subject to collapsing.