Showing posts with label erosion. Show all posts
Showing posts with label erosion. Show all posts

Thursday, 12 March 2020

Topsoil loss during 2020 flooding in the Clarence Valley


The Daily Examiner, 9 March 2020:

Anyone travelling around the recent flood-affected areas of the Valley, including along the Clarence River itself, couldn’t fail to notice the chocolate brown colour of those floodwaters.

The Orara River was particularly bad, and after the floodwaters had receded, council needed to use a front end loader to scrape thick layers of deposited mud off some roadways and bridges. The paddocks alongside creeks were likewise buried beneath a thick layer of mud.

This was always to be expected if torrential rain occurred soon after the bushfires, especially with ash washing off the bare ground into waterways.

But these floods brought more than ash. This was topsoil, something that is in short supply across much of the Australian continent. We are told that globally, some 24 billion tonnes of topsoil are lost annually through erosion, and Australia’s contribution is shameful, given we are a supposedly developed country with sufficient resources to protect this precious commodity.

Wind and water are the two main forms of erosion.

Both can be significantly mitigated simply by maintaining a good vegetation ground cover. Without that cover there is nothing to hold the soil, and this past season has highlighted that fact.

Firstly there was drought, and overgrazing to the point where only bare soil remained, resulting in one huge dust storm after another for months on end.

Then the bushfires destroyed what vegetation the livestock had left. Then came the floods, ripping apart fragile unprotected stream banks, and washing them downstream to the ocean.

Even without bushfires we lose far too much soil to erosion, and again, poor livestock management is largely to blame.

Many Australian rivers and creeks have no adequate vegetation to buffer against erosion and fewer still are fenced to exclude cattle.

As a result, these animals congregate along waterways, trampling banks, and browsing any available vegetation, so their impact is even greater than fire.

Landowners have a responsibility to manage erosion on their properties and to consider what they are leaving for future generations. If we are to solve the erosion problem, livestock management must be a focus point.

JOHN EDWARDS, Clarence Valley Conservation Coalition