There are many good reasons why land owners should care for their watercourse. These include:
Decreased erosion
Over-clearing and intensive development of a catchment results in more water moving quickly off the land surface in times of heavy rain. Often, river channels cannot carry this extra flow. If riparian land is not well-vegetated with deep-rooted plants, this can lead to flood-outs, stripping of topsoil from the floodplain, and accelerated bank erosion — all of these lead to the loss of valuable agricultural land. Replanting of deep-rooted species on riparian land can help to stabilise riverbanks, and protect them in times of flood. Well-vegetated stream banks are more resistant to under-cutting and slumping. Replanting riparian vegetation, in combination with in-stream structures such as rock riffle bars, can help to reduce head-cutting and other forms of streambed erosion.
Improved water quality
Good management of riparian land can decrease the amount of soil and nutrients moving from cultivated fields upslope of the riparian land into the stream. By trapping soil and nutrients, water quality is improved and the loss of in-stream habitat through siltation is prevented.
Healthy ecosystems
Good management of riparian land can prevent or minimise damage to both land-based and river ecosystems. Such damage can upset important biological balances and lead to the deterioration or even destruction of interdependent environmental systems. Riparian lands serve as corridors between tablelands and lowlands, and enable essential seasonal movement of species between the two.
Maintaining river courses
Increased flow from cleared land and unprotected riverbanks can cause rivers to change their courses and form new meanders or flood channels. This happens when the existing channel cannot carry peak flows, which overtop the banks and find a new flow channel. There are many examples where head cutting and meanders threaten roads, bridges and buildings. Healthy riparian vegetation protects banks and channels, reducing the risk of excessive erosion of meander bends or the establishment of new river channels.
Stock management
Stock that are allowed free and uncontrolled access to riparian land can directly foul the water with their wastes. They also increase soil erosion by over-grazing and through formation of bare walking tracks and pads. Both of these reduce water quality for downstream users. It is not uncommon for stock to fall down steep riverbanks or become bogged in riparian zones, resulting in injury or death to valuable animals. This is not only expensive for the stockowner, but can also lead to pollution of water supplies for downstream users. There is also evidence that animals drinking water polluted from upstream grow less quickly than those with clean water supplies. Stock may also contract bacterial infections when drinking polluted water. When water is contaminated with silt, manure or algae, animals are less inclined to drink, resulting in a drop in production.
Decrease in insect pest
Healthy, vegetated riparian land provides habitat for insect-eating birds and insect parasites that can help to protect pastures and crops from damage. It has been shown that losing even a small number of birds can allow significantly more belowground pasture grubs to survive and become adults.
Increase in capital values
Anecdotal evidence from real estate agents suggests that well managed riparian frontage can add up to 10% to the market value of a rural property. This is valuable whether the landholder wishes to sell the property, pass it on in good condition within the family, or use it as security for a financial loan.
Shelter effects
The shelter and microclimate which riparian vegetation creates can help to reduce death in newborn or newly shorn sheep, and lead to improved growth and productivity through reduction of heat or cold stress in animals. Vegetated riparian areas reduce wind speeds and this can assist growth and production of crops, as well as reduce wind damage to valuable horticultural produce.
Opportunities for diversification
Some landholders have combined riparian management with agroforestry production. Others have used riparian land for producing hay or other stored forage, or for growing firewood or specialist crops. These farmers have increased the diversity and sustainability of their property while, at the same time, protecting its most valuable land.
Retention of nutrient
In addition to preventing erosion and improving water quality, riparian vegetation can absorb and use natural or added nutrients that might otherwise be washed into streams, resulting in the growth of nuisance plants and algae within rivers. Sediment and nutrient can be trapped from overland flows and, in some circumstances, riparian vegetation can also utilise sub-surface flows of groundwater and the nutrients it contains.
Lowered water tables
Deep-rooted riparian vegetation may, in some circumstances, act to lower water tables along riverbanks, reducing the movement of salt and nutrients into streams from sub-surface flows.
Increased fish stocks
Healthy riparian vegetation helps maintain good habitat for aquatic animals, including insects and the fish that feed on them. Riparian vegetation provides important food sources including leaves, fruit and stems that fall into the stream. The roots of vegetation provide essential habitat by protecting overhanging banks, while large branches or trunks that fall into the water also provide shelter from predators and a diversity of flow speeds. Streams are an important recreational fishing resource and, in this way, can be a source of income for landholders and regional communities.
Landscape refuge
In drier environments, riparian lands act as vital refuges for plants and animals during drought or fire, and become reservoirs from which species can move out and recolonise adjacent areas when better times return. Riparian lands also act as corridors of natural vegetation, preventing species becoming isolated and dying out.
Decreased algal growth
Riparian vegetation helps to reduce light and temperature levels of stream ecosystems. It has been shown that this controls the growth of nuisance plants and algae, even when nutrient levels in the stream water have increased.
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Acknowledgement
Some of the information used in compiling this page was sourced from the following Land & Water Australia document:
Special thanks to Land and Water Australia for their assistance. Visit their website www.rivers.gov.au