Bush block near Ballarat - serious erosion problem

[lulu_slouch]

Hi everyone, I'm new to this forum and have just finished reading Back From The Brink. What a great book, I learnt so much!
A year ago, my partner and I bought a 20 acre bush block in Clunes (35kms north of Ballarat, VIC) and there is a badly eroded gully running through the middle of it. We’d be very grateful for any ideas on how we might successfully apply some of Peter’s ideas to our particular block of land.

Ideally, we’d like to try and prevent any further erosion in the gully and surrounding area, and gradually (hopefully) return the land to a more stable and fertile state. Eventually (in 5 or 10 years) we plan to build a small house and grow our own fruit and vegies, but have no plans for stock to graze on the land. So until we do that, I figure we have 5 or 10 years to do as much as we can to help it back to a healthy state.

Problem Areas (click on links to see some photos)
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1. Eroded gully – this gully is bone dry for most of the year, however in winter after heavy rainfall there is a small flow and puddles remain here and there for a day or two. The bed/bottom of the gully seems to have a mixture of clay in some places, and a sandy/rocky/shale in other places. The sides of the gully range in height from 1 – 4 metres and there are large trees growing right on the sides of the gully (some have fallen in or across the gully, due to the soil just falling away).
2. Land immediately either side of the gully is also eroding. There are huge holes in the ground where soil has just sunk away and disappeared, and it is easy to see that some of these holes are linking up and will just get bigger and bigger.

A couple of other points:
1. The plants/trees/shrubs on our block are mainly native, including Swamp Wallaby Grass, Small Grass Trees, Hedge Wattles, other Wattles (with yellow fluffy flowers), Yellow Box, Grey Box etc. Instead of a grass covering, we have a lot of moss and lichen, amongst all the leaf litter. The only weed on our block that I have found is a small thistle, which I will happily let grow, however it is only present on a small patch of soil that I think was previously brought in from another area to form a bridge over the gully.
2. Our neighbours land meets ours at the top end of our gully and they have built a huge dam there. So I think if the dam wasn’t built, we would’ve received a more regular flow of water into our gully, but now it’s all collected in their dam.
3. The block has a gentle slope up from each side of the gully for approximately 200 metres on either side to our fence lines. So when it rains, water runs down over the land and into the gully.

So some questions I have after reading Back From The Brink:
1. There are trees growing right on the edge of the eroded gully, so I won’t be able to flatten out the edges and create a shallower surface area without damaging or killing those trees. What should I do in this case?
2. Is there any point in planting willows in/near the gully? Most of the year the gully is bone dry, so I don’t think they’d survive. Are there any alternative trees that would perform a similar function but survive the harsh hot weather in summer and the cold temperatures in winter?
3. Same question goes for reeds, if I planted them in the gully, would they survive?
4. For the big gaping holes that are appearing in land near the gully, is there anything I can do to prevent them from getting worse and linking up to form bigger holes?

I am open to trying anything so any response will be greatly appreciated.

Cheers,
Louise

[duane]

Welcome Lulu,

What a great post.

Firstly, it was great to see your photos because they told an amazing story....in part.

All the erosion you see is caused by the effect of water, damaging what would have been in the past a very stable gully. The erosion you see in the gully now would have started its genesis as a head wall cut in a very sensitive area right at the bottom of that gully. This could have been caused by cattle eating out the the plants that keep this area stable. And the water did the rest, causing over time, the erosion to run all the way up the gulley.

In its current state, whenever, a rain event occurs now your gully is acting as an incised drain....rushing water and sediment out at an ever increasing erosive rate.

Your yellow soil (podsol) contains a lot of clay but because your soil fertility is LOW the soil looks to be suffering from possible tunnel erosion caused by this low fertility and this in turn causes a loss of microbes in the soil which leads to the erosion.

This is potentially a catastrophic and ever declining situation you are dealing with.

There are, however, a number of things you can do.

With regard to the gully:

You need to HOLT the ongoing incision.
If you have access to a machine I would suggest ,what you spoke about in your post--- that you push the banks in to fill the gully and flatten the whole thing out, ending up with gentle banks. Let the trees go in.

Then try and get a grass coverage by seeding at the beginning of spring after the winter rains and stabilise your banks with a native called Pittosporum undulatum and any other fast growing native tree....maybe White Cedar???. Try and choke the gully with Lomandra's and other native sedges and reeds.

With regards to thee tunnel erosion you will need to run some contours across the high part of your land which you can fill with mulch and have a mix biodiversity of plants both above and below the contour....see the Permaculture site for how to build these. There is a link in one of the blogs here.

What will happen over time is that gravity will carry water and fertility down your block and start to feed the soil microbes. You need to be very careful!!! because there may be HUGE eroded gaps under the soil which you cannot see from above and machinery and operator has been to disappear down these eroding tunnels.

Eco- organics had a similar problem with their farm in Victoria....Peter fixed it. You can goggle their website and email Greg Donahue.

[lulu_slouch]

Thanks Duane, lots of good info, much appreciated!
I've looked at Eco-organics website and their situation looks very similar to ours.
Thanks again,
Lulu.

[jeandb]

The globale water managment can also fight erosion and not only refill the water table.

How to?

The canals start on the side of a tream and send by a deep infiltration the water along the same level curve.

When there is a big storm with you get water and erosion in the stream ( durty ) . Make a dérivation of the stream along the same level curve like a large canal to have a low speed and get the decantation effect in this "decantation tank canal". At the end of this tank the water will be clean and can continue in the smaller level canal to be infiltrate along the way. But in the first part of the canal ( where the speed is slow ) you will get the deposite of erosion that you can push easily ( or catch to be put where you want ) on the down slop of the soil or enlarge the decantation tank.

see our website...
http://perso.wanadoo.fr/biefs.dupilat/