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Leaky Weirs

Posted: Wed Jan 26, 2011 7:37 pm
by ColinJEly
Firstly, congratulations to Peter on receiving his OAM. In his books Peter talks about things like 'leaky weirs'. It has recently been announced by those that survived the floods that in some cases they were worse than they had to be because some councils had been slack in cleaning up watercourses. Anyone got any comments? When things subside, it would be interesting to hear from those in the area who practise NSF.

Re: Leaky Weirs

Posted: Thu Jan 27, 2011 9:45 pm
by duane

You have been a long term follower of NSF and a long time contributor to this Forum.

i simply cannot believe you would pose or ask that question.

Have you not learnt anything about how this landscape once managed its water to rejuveante the landscape, restore its groundwaters and fill its floodpalin systems by preventing the minimum erosion from happening and allowing for the maximum flood to run across the landscape sustainably for thousands if not millions of years???

Don't you see a totally different landscape today?? One that is severly eroding, losing all its matter mostly out to sea. A highly incised and altered landscape that has turned all of out rivers, streams and creeks into deeply incised drains ripping the guts out of the land by waters destructive force.

I know you are aware that water, uncontrolled, is one of the most destructive forces on Earth but managed carefully it is also one of the most productive forces.

What you have stated
It has recently been announced by those that survived the floods that in some cases they were worse than they had to be because some councils had been slack in cleaning up watercourses
above is a comment that sees this destructive force as the NORM. It is now, for exactly the reason you have stated. The removal of instream vegetation and chokes was the very method used by our inique landscape to de-energise the destructive forces of water in this flat, fragile landscape.

We have removed all the plants from our wetland system and incised our waterways. These present day systems send water raging out of control like we saw in Qld recently which, horrorfied the whole country.

If you wish to see the same catastrophe repeated again, then do as you have hinted at.

May I humbly suggest, that you re-read Peter's books to get a clearer picture of the true way water once moved gently across our land building systems, NOT destroying them.

I know that you would NEVER advocate the latter Col. What you have quoted is sheer BS!!!!

Re: Leaky Weirs

Posted: Fri Jan 28, 2011 12:06 am
by Ian James
Duane, I am sure you must have misinterpreted Colin's question.

Colin can speak for himself but I read that he was commenting on the general ignorance among the population about water management. Not suggesting that water courses should be cleaned up.

Can you clear this up Colin

Re: Leaky Weirs

Posted: Fri Jan 28, 2011 7:00 am
by duane
More than happy to apologise to Col....if I misinterpreted his enquiry.

Re: Leaky Weirs

Posted: Fri Jan 28, 2011 8:22 pm
by ColinJEly
Friends One and All
In his books Peter talks about water flowing along on the 'high ground' because of the effect of the build up of silt from repeated floodings. Now presumably this only occurs on fairly level floodplains? During the 1998 bushfires I was at the camp at Licola, where we were pumping water up out of the creek some 20 metres below the surrounding ground level. On its journey down to the sea (or not in the case of the Hattah Lakes) even though we have a reasonably flat land, water will still flow downhill and there are some places, particularly in the 'mountains', where the stream level is quite some way below the surrounding countryside. Indeed there is a small creek (Mullum Mullum Creek) only a few streets behind my house in a council linear park where it changes from being a slow moving billabong to a fast flowing rock filled creek

We can contrast the current situation in Northern Victoria, where the floods are a slow moving blanket of water across vast areas of the landscape, with Towoomba and the Lockyer Valley, where the force of water was so great that it bent railway lines and floated entire houses down the creeks.

I am particularly interested in members who actually live in the flood affected areas, wherever in this great land that might be. What was the reality? How did things pan out in your own paddocks with your own swales?
Does Peter have any comment to make? I am sure it makes a difference between water slowly flowing over someones farm, to a fast moving flow inundating our little patch of suburbia?

Re: Leaky Weirs

Posted: Fri Jan 28, 2011 10:06 pm
by duane

The vast majoity of the Australian Continent is flat.

It has few mountain ranges that qualify as mountain ranges with the tallest peak being Mt Kosiosko at a little over 2200m. Hardly the Himalayas.

But there are high points it's true, usually in the upper catchments.

These by definition are highly erosive, coping with rainfalls, sometimes heavy that gets away quickly.

Many of these have had forceful rain events that have moved boulders and vegetation. They were never flat meandering systems like the vast area of the rest of the continent.

I can report that at Tarwyn Park in December 2010 they had reportedly a 1:100 year flood event. The oldest residents of the Bylong Valley had never seen such a flood.

Water covered parts of the floodplain that had never seen water since 1972.

TP is permanently covered in vegetation, the creek is not incised, it has densely planted wetlands and a whole series of contours which Peter had laid out 30 years ago.

It was a massive flood !!

During the peak of the flood the water thru TP was running out almost clear. Some parts of the floodplain were inundated for days, so that all of floodplain vegetation was under water.

When the flooding finally receded there was NO damage. The vegetation trapped 000's of tonnes of sediment, the ground water acquifers of the floodplains were full to within 300mm of the top of the soil and the vegetation survived intact.

The vast volume of water that passed over the property was de-energised by the wetland systems in the creek and the whole farm system has now been rebuilt and not destroyed. The contours in the high parts of the property captured water that leaked into the floodplain providing a positive hydraulic pressure which meant the plants did not drown.

Regarding the Lockyer Valley and Toowoomba, Peter and I were there 4 years ago to lookat a vegeatble farm that had almost run out of water. Water had been pumped dry from the groundwater with bores down over 100m deep. The creek was devoid of any instream vegetation and was only acting as an incised drain. Banks were unprotected with little or no vegetation. The land looked like a desert. Peter commented to the farmers gathered there that this valley was in severe decline and a flood could potentially do untold damage because the land had been strpped bare and mined beyond it's capacity. The fllod that came doen the Lockyer moved with such violent force that it picked up all sorts of flotsam and jetsam and this together with the velocity of water caused immense damage. It was always a disaster waiting to happen. But we never imagined it to be as bad as it was. All of the natural processes that once would have provided protection to the landscape in the Lockyer had been removed over decades. The practices of the past have unlocked the huge potential for the increible disasters we are seeing today. Sure Nature delivered the rain. But we have destoyed the fragile landscape that had evolved mechaisms for dealing with such high rainfall events. This is going to happen again.

However, on a more positive note, in Victoria, a farmer that has engaged NSF techniques, has reported that in his place in Barjarg is doing amazingly well. He has installed leaky weirs to his creek and contours to replicate the previous high water systems in the landscape. "NSF has held up and been good. The heavy pasture burden we have prevented any paddock erosion. We still have water running out of the ground in different places in most paddocks. Its fantastic."

Meanwhile in the Fitzroy Valley a number of farms there have implemented NSF. They have all reported in on the successful outcomes their properties have had following the massive flooding there.

Another farmer in SE Qld reported "we got away with minimal damage at the farm. I'm certain the nsf work had very beneficial effects, particularly strengthening the soil and pasture health and holding the soil together under the water pressure." His property is up near Toowoomba.

The aim of Peter's work and that of the Australian landscape is/was always to slow and de-energise water by moving water against water.

A landscape where vegetation is cleared from streams, where creeks have been allowed to become incised drains, is simply a recipe for potential disaster in times of heavy rainfall.

This landscape managed these 1:200 and 1:100 year flood events for thousands of years, building systems. Our intrusion onto the landscape has disassembled all the landscape components that managed floods and prevented water escaping quickly to the sea.

Once these floods would have moved even MORE slowly across and over the landscape, flowing gently, refilling dried and cracked clay soils and spreading mulch to the high ground. Sometimes it took 12 months to get floodwaters from the top to the bottom of the MDB. We have increased the speed by which water moves across and through our landscape and we not Nature are responsible for the devastation we are witnessing.

We must learn how the landscape once managed this flooding/drought prone landscape which allowed for the building of a fertile system that grew huge megafauna.

We need to accept that we have dismantled it but the good news is that in many areas we can biomimic the original functions of the Australian landscape to deal with all of the issues of flooding and droughts.

I will be doing a more indepth report on all these farms in our next national newsletter.