Riparian Zones

What is the Riparian Zone?

The riparian zone is that special place where "the land meets the waters" and in doing so creates an environment that carries out vital functions for life and landscape. The riparian zone is all land that directly surrounds any landlocked waters including floodplains and wetlands, stream gullies and river valleys. All rainfall runoff must pass through the riparian zone before reaching the waterways.

What is so special about the Riparian Zone?

In a continent as old and dry as Australia our inland waterways are literally the life blood of the land. In the wet season they function to drain away excess waters from inland areas. In the dry they function as vital refuges for both wildlife and primary industries. Australian fauna have adapted to our extreme climate becoming dependent on specific places for drought refuge. Riparian areas are critical survival zones for the 1:100 and 1:1000 year droughts.

In Australia 80% of all birds are dependent on riparian areas for at least part of their life history. Forty-three species of birds of the eastern Australian highlands have been identified as having their life cycles intimately linked with water courses.

There are many vertebrate groups other than birds, which have close associations or even dependencies upon riparian areas. Reptiles such as the water dragon live and hunt within the zone. Up to nineteen species of bat frequent or inhabit riparian habitat. Many other non-flying mammals also frequent the zone. Obvious inhabitants of the riparian zone are frogs whose life cycles are inextricably linked with riparian habitat. Most species of frog live close to water, aquatic frogs in particular. Nearly all frogs migrate, seasonally to ponds and streams.

The platypus (Ornithorhynchus anatinus occurs in Tweed Shire) is Australia's most aquatically adapted mammal, or more specifically, a Monotreme. The platypus can only exist in areas where the riparian zone is intact . This also applies to the Water Rat (Hydromys chrysogaster   which also occurs in Tweed Shire) and the False Water Rat (Xeromys myoides) whose southern range is just outside the Tweed.

The Raindrop’s Story

When it rains water strikes the earth as raindrops and quickly moves over the land following the slope of the ground. As rain hits the ground it begins to pick up the soil and debris in it’s path. The water will carry this material until it is slowed down allowing the water borne particles to drop out of the water column. This is where riparian vegetation comes in. The binding roots of the plants in the riparian zone act to slow down the rate of soil removal from stream banks. They also act in conjunction with fallen leaves and branches to slow down the rate of overland flow of waters which allows much of the water borne soil and debris to deposit before reaching the stream. This makes Riparian lands very fertile, with an abundance of topsoil and water.

Other important functions of riparian vegetation include its ability to reduce the amounts of nutrient and other pollutant inflows to streams. Roots and organic materials help to bind and uptake a broad range of pollutants that would otherwise enter our waterways.

Although these lands are fertile and resilient, they are also fragile. Remove or change the protective vegetation from a waterway and all of the qualities that make the Riparian zone such a special place may well collapse into the waterway with the topsoil, turning it into a drain.

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A Legacy of the Past.

Before white settlement in coastal Northern NSW there were vast networks of forests and wetlands. The Big Scrub Rainforest which encompassed a massive 75000 Ha dominated our region. It represented the largest of the subtropical rainforests in Australia.

If you took a Sydney phone book and ripped out two pages, those two pages represent all that now remains of that once vast primeval forest. What is left to us of these once great forests can largely be found in the riparian zones of our rivers and streams.

Stotts Island on the Tweed River represents one third of all that remains of Lowland subtropical riparian forest in Australia. Needless to say, Stotts Island is a special place. It is where we can go to learn about how those once vast forests functioned and how we can begin to address the problems that have been caused by their removal.

The vegetation that now fringes the Tweed and other rivers and streams in our region is largely made up of exotic species. We have introduced many and varied plants from all over the world for the purposes of agriculture and because Australians as a nation have a passion for gardening.

The Challenge for the Future.

The forest systems that existed along our waterways took thousands perhaps millions of years to establish and in under a century we have destroyed all but 2%.

Exotics are by far the biggest threat that now faces our remaining native ecosystems. Because foreign plants have few predators and diseases they easily out compete our stressed native remnants. For riparian lands, exotic weeds spell disaster. Rivers act as major highways for the spread of exotics. Exotic vines can become so thick that they can collapse not just individual trees but entire forest canopies. With such destructive powers it is vital that we begin to address this problem as a community.

As a community the best place to start to fix the many problems that face our waterways is in our own back yards. Particularly those who live near waterways can help by growing local native plants in their gardens. A guide to the appropriate plants for gardens adjoining waterways in the Tweed region is currently being compiled and will be available at your local nursery or Council Offices by the end of December 1999.

Much more can be achieved if you decide to join a Local Landcare or Rivercare group. For more information on these groups please call Department of Land and Water Conservation and speak with

• Kate McKenzie (Landcare Coordinator)  on (02) 66 725 488.

Further information is available through

• Tom Alletson (Waterways and Coast Coordinator)
  Tweed Shire Council   02 66702400