Rocks that fall down mountainsides end up in rivers. The rocks are carried downstream by floods. When the slope of the river flattens out on the plains, the rocks are set down. In big floods the rocks and sediments are carried out across the plains toward the coastline.
Braided rivers are made when these rocks and sediment build up on the riverbed. In time the build-up becomes so high that the water begins to flow down a new channel. These changes happen all the time and are a key part of braided river systems. This is also part of the reason these rivers are such productive ecosystems.
Flora and fauna
About 26 bird species feed and breed on our braided rivers. These include:
- Ngutu pare/wrybills
- Tōrea tuawhenua/South Island pied oystercatchers
- Kakī/black stilts
- Tuturiwhatu/banded dotterels.
A few seabird species breed along braided rivers too:
- Tarapiroe/black-fronted tern
- Tara-nui/Caspian tern
- Tara/white-fronted tern
- Kawau/black shag
- Tarāpunga/black-billed gull.
Invertebrates and lizards
Braided rivers and wetlands are home to many aquatic invertebrates such as:
- red coat damselflies
These invertebrates are a food source for fish and birds.
Lizards are also found around braided rivers, such as:
- McCann’s skink/mokomoko
- long-toed skink
- scree skink
- spotted skink
- jewelled gecko.
Some fish live in braided rivers and their connected wetlands. Some of these fish are:
- lowland longjaw galaxias and upland longjaw galaxias
- longfin eel/tuna
- Canterbury galaxias
- alpine galaxias
- upland bully
- common bully.
Braided rivers are also home to popular sport fish such as trout and salmon.
Braided river plants
In braided rivers there is a range of low growing plants. These plants are able to grow amongst shifting gravels, hot and cold temperatures and few nutrients. Some special plants are the forget-me-not and the rare tiny woodrush. Others include mat daisy and the native daphne/pinatoro.
Important for people
People use braided rivers for recreation such as jet boating, fishing, walking, bird spotting and swimming. They are also an important tourist attraction.
Braided river-mouths are culturally significant for Ngāi Tahu. The Waitaki River is the ancestral river of Ngāi Tahu. The Waitaki River was a key provider of mahinga kai resources and a way of travelling by reed raft (mōkihi).
Where are braided rivers?
This map below shows the braided reaches of the 163 braided rivers in New Zealand. The larger rivers from each region have been labelled.
Braided rivers are under threat from:
- weeds that stabilise the naturally changing water channels
- predators that prey on native birds, lizards and insects
- introduced fish that compete with native fish species
- the use of water from rivers for electricity generation and irrigation
- people who may crush bird nests and chicks with vehicles or scare birds from their nests. This leaves eggs and chicks open to predation and weather extremes.
How can you help?
- Riverbed birds nest between July and February. They need special consideration during this time.
- Keep pets away from riverbeds and keep dogs on a leash at all times.
- Keep clear of nesting colonies and watch out for eggs and chicks. They are hard to see and very fragile.
- If you disturb birds accidentally, move on quickly so that the birds can return to their nests.
- Try not to drive vehicles on riverbeds. Park on the bank and walk to where you want to go.
- The speed limit for boats is 5 knots within 200 metres of the bank. Jet boats disturb birds and wash away nests.
- Above all, respect braided rivers and the plants and animals that live in and around them.