River life cover
Publication summary and introduction
Braided rivers
Gravel-based braided river systems are found in only a few places around the world; Alaska, Canada, the Himalayan region and New Zealand's South Island have excellent examples. They all flow from geologically young, rapidly eroding mountain systems and are characterised by wide gravel or alluvial beds, many winding channels, and highly variable water flows.
In the South Island, the largest braided rivers are found on the eastern side of the Southern Alps/Kä Tiritiri o te Moana, especially in Canterbury. By the end of the last glaciation, 10,000 years ago, rivers carrying alluvium down the valleys of the east coast had spread it amongst glacial deposits to form flat basins between the mountains and the coastal plains.
The floor of the Mackenzie Basin has been formed from sediments deposited by the Tekapo, Tasman/Te Awa Whakamau, Ohau, Hopkins/Te Awa äruhe, Dobson/Otao, Cass, Pukaki, Macaulay and Ahuriri rivers. The process of geological uplift, erosion, and alluvial transport continues to maintain the braided rivers today.
Braided river species
New Zealand's braided rivers are distinctive, dynamic environments with specialised plant and animal communities. During spring and summer, at least 26 species of water birds feed or nest on braided rivers. Some of these birds are now threatened or critically endangered. In addition to birds, braided rivers provide important habitats for numerous plants and other native animals.
Some of these species such as the kakï/black stilt, wrybill/ngutu pare, McCann's skink/mokomoko, native fish and insects will be profiled in this resource, and are each interesting to study in themselves.
Habitat under threat
Unfortunately, the braided river habitat and surrounding wetlands of the Mackenzie Basin are under threat - from introduced species, habitat loss and the development of hydro-power schemes, as well as agriculture. These issues are discussed throughout this resource.
Project River Recovery
A programme called Project River Recovery (PPR) was created in 1990 in recognition of the importance of braided river and wetland ecosystems in the Mackenzie Basin. Its focus is to enhance braided river and wetland ecosystems in this area, and to maintain populations of native plants and animals. This project will also be profiled in this resource.
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