A catchment is an area of land drained by a system of streams. The health and condition of the river reflects the health of the catchment. Maintaining or enhancing the health of catchment resources such as soil, water and native vegetation will directly and indirectly maintain the water quality of a waterway.
A riparian corridor is the land directly adjacent to (or surrounding) a natural or artificial waterway, including:
Riparian land extends from the edge of the waterway onto adjacent terrestrial land. The width of a riparian zone may range from very narrow through to a wide, densely vegetated corridor. The width is dependent on location within the catchment (gorge, valley or floodplain) and the adjacent landuse (agriculture, forestry, National Park or urban development).
Riparian corridors provide a crucial link between terrestrial and stream ecosystems and form a unique and distinct unit within the surrounding landscape. However, since European settlement of Australia, riparian areas have often been highly modified.
The riparian zone generally consists of three zones, the top, middle and toe of the bank. Each zone supports a diverse mix of vegetation. A healthy riparian zone usually has a diverse range of plant species and well-structured vegetation community that consists of canopy, understorey and groundcover plant species. Some plants can be found in all zones, whilst others are confined to a single zone. The riparian zone performs a range of valuable functions, which is described below.
The importance of riparian corridors
1 Habitat for terrestrial wildlife.
Native vegetation provides food, and shelter. It can also provide a corridor for the movement of wildlife and refuge during drought and bushfires.
2 Food, shade, and shelter for aquatic organisms.
Riparian vegetation provides detritus or vegetable matter, which breaks down and provides food for aquatic invertebrates. Shade from riparian vegetation helps maintain cool water temperatures in pools. In addition, fallen branches, large woody debris and aquatic plants provide habitat for instream fauna such as native fish and crustaceans.
3 Bank and bed stability
Native riparian vegetation is important in the prevention of streambank erosion. Vegetation binds soil and provides "roughness" that reduces flow rates, particularly during flood events. Vegetation at the "toe" of riverbanks is especially important to riverbank stability, particularly on outside bends of meanders and on other banks where flow is deflected.
4 Buffer to nutrients and sediment.
Vegetated riparian zones maintain water quality by filtering sediment and nutrients, and reducing the amounts entering a watercourse. Any vegetation that provides a dense cover at ground level will be an effective buffer.
5 Aesthetic benefit and intrinsic value.
Riparian vegetation has an inherent aesthetic and intrinsic worth that is difficult to value in monetary terms. Different people value the aesthetic or intrinsic features of riparian areas differently. This often depends on their association with and understanding of these areas. For many landowners the aesthetic appeal of trees on farms is a primary motivation for wanting to manage river and creek systems.
Economic benefits of managing riparian corridors
There are many economic, as well as environmental, recreational and social benefits assoicated with sound management of riparian areas. The following are just a few of the ways in which landholders can gain economic benefits from managing their riparian corridors as a different, but integral part of their while farm system.
C Easier stock management
Rivers and streams can be difficult areas for stock management for the following reasons:
Appropriately located fences and watering points can save time and reduce stock losses.
C More even grazing and better utilisation of pastures on river paddocks
Generally the highest grazing pressure on pastures is near water. By spreading watering points, it is possible to get a more even spread of grazing and better utilisation of pastures.
Options for providing alternative water supplies include:
Many landholders that have installed alternative water supplies find that stock prefer these as a watering point to rivers and creeks.
C Reduced levels of water borne stock diseases
Overseas studies have shown that in some areas water borne diseases can have a significant impact on herd productivity. They are often spread by stock defecating in water bodies when they are drinking. Overseas studies have indicated that milk production of dairy cattle will increase as a result of improved water quality.
C Reduction in losses of land and infrastructure to riverbank erosion
Riverbank erosion is a natural process. The rate of erosion can be accelerated by activities such as gravel extraction, clearing of riverbanks, and any activity that results in soil erosion and sedimentation of watercourses. On some properties large areas of land have been lost to riverbank erosion. Riverbank erosion commonly causes loss or damage to infrastructure such as bridges, pumps, buildings and fences.
C Reduction in losses from rats in sugar cane
Studies in North Queensland have shown that rats can cause significant losses of production in sugar cane. Healthy riparian vegetation can shade out grasses along creeks which is a natural habitat for rats, and reduce rat numbers.
C Improved capital value of land
Indications from real estate agents are that properties that are well laid out, and have well-managed riverine corridors, will sell for considerably more than average market value.
C Increased fish stocks
Riparian and aquatic vegetation provide food and habitat for aquatic ecosystems. The fishing industry relies on this basic natural resource. Particularly important vegetation to the fishing industry are areas of mangroves, melaleucas (paper barks), and wetlands.
Some practical ideas to consider
Riverine areas are a distinct "land type" that should be managed differently from the rest
of a property. Consider the special attributes of these areas when planning
a property.
Consider establishing "river paddocks", with the fence located above flood level. River
alluvial soils are often very fertile and productive, with a higher land
capability than other parts of the property. They are useful areas to grow
crops and improved pastures. Many landholders use these paddocks for periodic
crash grazing, or for drought fodder. Spelling of these paddocks from grazing
will assist in the natural regeneration of riverbank vegetation.
Temporary electric fencing
can be used to regenerate
native vegetation. In many areas
exclusion of stock for 4-7 years will allow native vegetation to regenerate,
and to become mature enough to resist grazing pressure.
Fence out areas where mustering
is difficult or where stock often get bogged. This is generally cost effective in the longer term if fencing costs are not too
high.
If stock are watering from
a creek or river, use fencing to guide them to stable access points.
Also if stock are regularly crossing a creek, use fences to guide them
to a stable crossing
point.
As the saying goes, "prevention is better than
a cure". It is often better
and more cost effective to protect a riverbank that is in reasonable condition,
than to restore it once it is degraded. Generally the riverbanks that are
most prone to erosion are those that deflect river flows. Examples include
outside bends of meanders, and banks adjacent to in-stream bars or islands.
These areas should have the highest priority for protection.
Look for multiple benefits from any revegetation that you do. For example,
strips of vegetation could not only stabilise an eroding gully, but protect
pasture and livestock from winds and be used as an area to supplement feed
for young livestock.
If you are planning to
establish buffer
strips for sediment or nutrients,
they should be placed as near as possible to where soil starts to become
mobile during storm events. Ideally buffer strips should be placed on small
drainage lines where water begins to accumulate in the paddock. Provided
there is sufficient ground
cover, a grass and reed buffer
strip can be as effective as native vegetation buffer strips.
Most nutrients and
other pollutants
attach strongly to soil particles. By
trapping the sediment in run off, it is possible to greatly reduce nutrients
and other pollutants entering waterways.
Many rivers and creeks
have natural levee
banks. Nutrient and sediment buffer
strips don’t work very well if located on these. Run off water from
adjacent paddocks will usually flow into small riverside channels, and
not flow over the levee bank.
Wetlands are important, as they trap sediment and nutrients
and act as a "sink". The ability of wetlands to trap sediment
and nutrients can be enhanced by reducing grazing pressure. This allows
sedges and other wetland plants to come back.
Q. Will the natural vegetation on the river or stream bank regenerate if it is fenced off?
A. This is very much dependant on the conditions at the site. Factors that will influence the amount and type of regeneration include:
Seed sources – It is essential to have a viable source of native seed nearby or in the soil. If there is no seed source them replanting may be necessary in order to re-establish native vegetation.
Competition – Weeds often proliferate when stock are removed from an area. This can include woody weeds, exotic broad leaf species, or introduced grasses. Some form of weed management is often needed to assist natural regeneration. However in many instances weeds will naturally disappear as shade is reestablished and soil disturbance by stock is eliminated.
Disturbance - Fire or soil disturbance can promote the regeneration of many native species. Fire can also promote weeds, and kill fire sensitive native species. Therefore it is important to manage fire in areas of natural regeneration. Fire should be excluded from areas where rainforest species and most riparian species such as Lilly Pilly (Syzygium sp.) are regenerating, or where it is likely to promote vigorous weed growth. In other areas, frequent fires should be avoided as this will kill seedling regrowth of native trees and shrubs. Fire frequency should be matched to the sensitivity and seeding cycles of the vegetation type.
Climatic conditions – Climatic conditions will influence the survival of regenerating native vegetation. Long dry periods, severe winds or frosts can kill or retard regenerating seedlings.
Q. Are river oaks good or bad?
A. River oaks (Casuarina cunninghamiana) are a native species that colonise river bars, and riverbanks. They are a useful species for stabilising the toe of eroding riverbanks because they are fast growing, and can resist flood flows when growing on sand and gravel bars. Avoid planting them on eroding mid or upper banks as they have an extensive shallow root system. Large trees can destabilise substantial sections of bank when they fall into the river during flood events. They can be managed by selective lopping to ensure a range of native species can establish before they become too large.
River oaks are a very valuable food source for terrestrial birdlife such as the Yellow-tailed Black Cockatoo and for aquatic organisms as the needles rapidly decay in water.
Q. What should I do about invasion of weeds when I fence off the river/stream bank?
A. There are a number of methods that can assist in controlling weeds and allowing native vegetation to regenerate. These include:
Removing stock at the
optimal time for regeneration of native plants –
Grazing temporarily reduces weed competition
to native species for a short period after the stock have been removed.
Ideally stock should be removed at a time when most native species are naturally
germinating. This is usually in the wetter months of the year.
Selective weed control
around natural regeneration –
Selective weed control around individual plants
or groups of plants can assist them to survive. There is a range of chemical
and physical control options that can be used, depending on the situation.
Often native vegetation will regenerate with minimal weed control, or with
no weed control at all.
Permits to remove vegetation from riparian areas may be required. Contact your nearest Department of Land and Water Conservation office to seek advice.
Q. What are the best species to plant on my river or stream bank?
A. The best species to plant are naturally growing local native species. These species are well adapted to the local conditions, and require minimal maintenance once planted. Many of these species are available through local nurseries or markets. Local landcare and bushcare coordinators may be able to direct you to local growers with suitable species. Alternatively, landholders can collect local seed and grow their own local native plants in their back yards.
Q. How do I stop my fences being damaged in floods?
A. Here are some options for minimising damage to fences from floods:
Ÿ Fence out "river paddocks" with fences above flood level.
Ÿ Use "drop" fences. "Drop" fences are designed so that they can be laid over prior to a flood, or so that they drop from their anchor points under the pressure of floodwater.
Ÿ Wherever possible run fence lines parallel to the direction of flood flows
Ÿ Fences running in the same direction as flows tend to be damaged less by floods. If you need to fence across the direction of flow consider having short sections of "sacrificial" fencing, or "drop" fences.
Ÿ Use portable electric fences in flood prone areas.
Ÿ Use "hanging" fences if you are fencing across creeks.
Ÿ Locate fences on natural river/creek levee banks. Many creeks and rivers have natural river levee banks. These areas are higher than surrounding areas and much less prone to flooding.
Q.
Are grass pastures
effective in protecting river/stream banks from erosion?
A. Grass pastures can be effective in stabilising banks where there is little or no flow pressure during flood events. This includes straight sections of rivers/creeks or inside bends of meanders. "Runner" type pastures such as kikuyu are more effective than grasses that form tussocks. Grass pastures are not as effective as native vegetation on actively eroding banks, outside bends or on banks which deflect flood flows.
Q. What funding or incentives are available for riverbank management?
A. The following incentives may be available for riparian management activities.
Taxation incentives
Ÿ 34 cents
in the dollar rebate (section 388-A of the ITA Act 1997) or deduction (Section
387 – A of the ITA Act 1997) for landcare operations, or for conserving
and conveying water.
Ÿ Deductions for normal business expenses repairs (Section 8-1 of the ITA Act1997).
Ÿ Deductions for the cost of repairs (Section 25-10 of the ITA Act 1997).
Ÿ Depreciation of plant and equipment (Section 42-15 of the ITA Act 1997).
Grants
Ÿ From time
to time State Government grants are made available to landholders for vegetation
management/conservation, water conservation, and other land management activities.
Ÿ The Natural Heritage Trust provides grants to landcare and other community organisations for activities related to river management, including river restoration, revegetation, and protection of native vegetation.
Ÿ There are a number of grants that are accessible for riparian corridor restoration projects. These are mainly available to landcare and other community groups.
Further information and assistance of riparian areas can be obtained from the following contacts:
R Your local office of the Department of Land & Water Conservation, landcare group, catchment management committee or Greening Australia Branch
R Land and Water Resources R & D Corporation (LWRRDC)
GPO Box 2182
Canberra ACT 2601
(02) 6257 3379
R Clarence Catchment web site: www.nor.com.au/environment/clarencecatchment
R Riparian Corridor Management Project for the Clarence Catchment.
This brochure was funded by LWRRDC and produced on behalf of the Clarence Catchment Management Committee.
Assistance in the development of this brochure was gratefully received from Simon Proust, Farming for the Future; Fiona Nagle, Rivercare Officer; Siwan Lovett, LWRRDC; and Terry Moody, Upper Clarence Farm Forestry Office.
Text: Matt Foley and Angela Ridgway
Design: Angela Ridgway.
Updated January 2000
