The Guardian

The Guardian May 8, 2002


Culture and Life

by Rob Gowland

Of riffles and riparian vegetation

When the explorer Alan Cunningham came upon the upper Hunter River in 
1825, just above its junction with the Goulburn River, he found the Hunter 
to be less than 50 metres wide, but too deep for pack horses to cross.

Today, the Hunter at that point is a shallow, sediment-filled river some 
300 metres from bank to bank. Packhorses would no longer have a problem, 
but the alteration in the shape of the river channel is far from a cause 
for joy.

The dramatic change is traceable to the removal of timber in the river's 
catchment area and especially the clearing of vegetation from riverbanks 
(riparian vegetation). These acts lead to erosion of riverbanks and 
increased run-off from previously timbered areas with correspondingly 
increased silting of the stream-bed.

By a complex chain of inter-locked effects, it also leads to increases in 
the amount of sediment the stream can carry (and deposit downriver) and in 
the velocity of the stream. As a result, the natural system of pools and 
riffles that regulates and dissipates the energy of a river is lost, 
resulting in further  accelerated  erosion.

There is growing awareness nowadays of the importance of riparian 
vegetation, just as there is more awareness today of the value of trees and 
the long-term benefits of not clearing land. Hilltops bare of a single tree 
are no longer viewed as good sheep country won from the wilderness but as 
erosion waiting to happen.

This is not some discovery of our enlightened present, however. Exactly 100 
years ago, J H Maiden, Government Botanist of NSW, in discussing the causes 
of floods on our old friend the Hunter River, noted that "the innumerable 
sheep tracks are accentuated and the ground everywhere is pulverised by the 
feet of the sheep wandering after the scanty herbage.

Pulverised soil

"When the rain falls much of this pulverised soil, carrying with it grass 
plants and seeds of grasses and various forage plants must be washed into 
the creeks and again into the Hunter, which becomes discoloured.

"There is evidence everywhere of broadening streams, of banks breaking down 
and good soil washed away."

Almost half a century later, in 1948, the Hunter River Flood Mitigation 
Committee observed that "there is little doubt that the wholesale 
destruction of timber over the years has contributed largely to the erosion 
of the countryside and the breaking down of the riverbanks".

The following year there was a catastrophic flood on the Hunter, followed 
by an even worse one in 1955.

What is different today is that we now have the benefit of numerous 
scientific studies showing that streams with well-vegetated banks are 
narrower and deeper  and hence generally "healthier"  than those 
without.

There is a slowly dawning recognition of the necessity to actually keep the 
riparian zone on either side of a waterway free of stock. But the average 
Australian farmer has enough on his plate already without having to build 
fences along any rivers or creeks on his property.

However much a farmer might agree with the spirit of conserving the river 
channel, under the conditions of private, individual farming that prevails 
in Australia, few farmers would be able to give much of their time or 
energy to being concerned about the state of the river bed.

Privatisation

There is tremendous expertise and knowledge on specialist topics like water 
and catchment conservation already in the relevant government departments 
and agencies. This resource is in grave danger of being lost through 
privatisation.

Because government departments are not in it for the money but to serve the 
populace, they can freely and readily draw upon contributions from the 
scientific community, natural resource managers, local government, 
researchers, community groups, and interested individuals to prepare 
environmental reports that have no commercial axe to grind.

At the recent Small Farms Field Days at Tocal, in NSW, I picked up a copy 
of the NSW Department of Land and Water Conservation's State of the Rivers 
and Estuaries Report for the Hunter, Karuah and Manning Catchments.

A splendidly produced publication, it is intended to assist "the community, 
land owners, government and other interest groups" in ensuring that natural 
attributes  from rivers and wetlands to ground water and "aquatic biota" 
 are protected, rehabilitated or conserved.

The drive to corporatise and privatise government departments means not 
only the loss of jobs and services, but the destruction of an essential 
public intellectual and scientific resource.

Over time government departments almost by default develop a large and 
unique body of expertise that can never be duplicated by smaller competing 
private companies. To dissipate this human resource, to scatter that wealth 
of knowledge, is surely a crime against the common good.

Private companies can research the causes of riverbank erosion, of course. 
But they will do it in the interests of whoever has commissioned them, and 
they will go no further than necessary to earn their fee.

In researching and formulating policy on the environment, as in everything 
else, public is best.

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