La Nina

24 08 2022

When I arrived in Tasmania for good almost seven years ago, Tassie was in the grip of its worst drought ever according to reports I was accessing at the time. Not that it looked like a drought to me having just left parched Queensland. But all the same, it was so dry I reversed my 2WD ute right down to the edge of the dam to collect all the trash from a tree I felled into said dam. Today I wouldn’t reverse the 4WD down there, I doubt it would come back up the slope! That’s how wet it’s been, and now they’re forecasting another straight third La Nina for the coming year. I suppose that if I had to choose between bushfires caused by El Nino and flooding rain I might choose the latter.

I’ve been waiting years to finish behind the house. The pandemic hasn’t helped of course, I’ve been topping up the berm where it’s settled with anything I could get including twenty tons of what the council calls mulch all moved with the old trusted ute. It still wasn’t enough. I then got wind that a builder on the other side of the valley was getting rid of topsoil, but refused to deliver it this far until I doubled their asking price. With staff shortages caused by the pandemic, it took a month before the first of two ten ton loads arrived. If only they’d managed to come earlier before the wet……. yes the truck got bogged!

Terry the driver dumped as much as would come out the back, but it was stuck alright. So I then rang Matt my neighbour to see if he’d come here with his digger to pull the truck out, after several unsuccessful attempts by yours truly with the the 4WD. There’s only so much a ute can do….

With the truck back in action, the rest of the soil was tipped out and he went back for the second load while Matt spread the black stuff where I wanted it. I ordered the soil sight unseen, that’s how desperate I was! Luckily, it turned out to be way better than expected, the pH is even neutral and it came with worms included!

I then bought half a bag of green manure seeds and rotary hoed them in for good measure. Plus it broke up all the clods, the soil was very wet….. And about to get a whole lot wetter!

Heavy rain had been forecast for the following day, but nobody was expecting what happened next. It just poured. And poured. The rain event to break all records. The Kermandie River broke its banks and flooded the lower portion of Geeveston.

Residents were even evacuated, it was bedlam. Meanwhile, behind our house the newly laid soil was unable to absorb any moisture and the area was starting to resemble the dam at the front of the house! Said dam by the way rose half a metre in 24 hours and it’s still the fullest I’ve ever seen it, continuously overflowing….

In a panic, I got out in my wet gear and started cutting a drain with a shovel, something I was going to do anyway, just not in pouring rain. Flowing like a torrent, the new drain simply couldn’t keep up with the deluge coming down the hill behind the house. And you guessed it, water came in the house…….

It wasn’t a huge amount of water, but enough to be a real pain, disrupting anything else we had planned. In the end we set up a syphon with a garden hose and it more than kept up with the water ingress. The water behind the retaining wall came up a lot higher than any other previous time and managed to actually get into the electrics inside the concrete filled blocks, tripping the earth leakage safety switch, so that now half our power points aren’t usable. It will dry out but it’s anyone’s guess how long that will take. It will be a week to remember!

The sun’s come back out and I’ve finished digging the swale/drain behind the house to catch future deluges. Now I hope that the green manure seeds don’t rot before germinating.

A dozen fruit trees have been planted in the new soil and the green manure is hopefully doing its job. I’ve since slashed it into mulch and it’s growing back blocking out weeds. With any luck we’ll have a food forest next spring..


After waiting months for Jordan (who reroofed the old shed a couple of years ago) to come back with his digger, we now have further future proofing for the Fanny Farm. The terrain, like most of the land here, was shaped many decades ago for growing apples. Windrows going straight up and down the slopes mean that in heavy rain the water runs straight down the hill. The heavier the rain the faster it goes! And the deepest one went straight through the chicken pen and to the back of the house.

We now have a spoon drain to Intercept any downpour coming down the 25 acres above our back fence, and the soil cut out to do this was used to fill all the ditches between the windrows…….. So now I have a flat surface to drive on whenever I need to. I’m already planning to grow some trees there as a windbreak for the occasional strong southerly winds. The water will be diverted to another windrow much further to the west which will take the rain to the dam.



13 responses

24 08 2022

Gee, you built in a flood plain, of some type, or a real low lying area, by the look of it. Did you know that this could be an issue, at some point down the track? When i built, about 4 years ago, i only chose the site because it had a couple of degrees of fall from front to back.. I did a few courses in building, drainage and still wasnt 100% convinced, that i understood the likelyhood of a flooding situation, so i added a crushed rock drain and built the house on stumps, joists and bearers, with a minimum of 1 meter clearance underneath. I have birds that block the downpipes, with nests, but that’s the worst of it, so far. How much room, or freespace do you have in the subfloor?

24 08 2022

This is no flood plain, we’re at 95m above sea level but there are 25 acres of sloping pastures behind us. And the house is literally a dam. All the drainage is double what the engineer said to install but it was all overwhelmed. I have plans to intercept any future flooding higher up, but I have to wait for everything to dry before I do any further earthworks.

24 08 2022

BTW that photo of flooding is 2.5 km from us and all downhill from here….

24 08 2022

No subfloor, it’s a slab. You cannot build a ten star energy efficient house on stumps.

24 08 2022

Ouch. That is some weather. But congrats on getting a steal of great soli.

24 08 2022

Yeah, the local landscaping people sell a small ute load of maybe 800kg of “garden soil” for $90. This 20 ton delivery cost us $800 and involved no driving on my part.

24 08 2022

24 08 2022

This is what our floodplain looks like!

24 08 2022
Hamish McGregor

“And you guessed it, water came in the house……. ”

Was that through the rear concrete wall, or the front where the windows and doors are all located?

I am an immense fan of earth sheltered buildings. Tanking, French drains and slopes to encourage run-off are all critical.

“All the drainage is double what the engineer said to install but it was all overwhelmed”

Is your slab at the mercy of a rising water table? My fear would be damp induced mold.

25 08 2022

It came in between the slab and the very bottom course of concrete blocks. There must be a weakness of sort there. The block layer laid the first course, and I installed all the electric cables on top of it (in conduits of course). I core filled that first course by hand, and the blockie came back later to raise the walls to full height. I should have added waterproofing to the concrete I poured into those blocks, and maybe I should have filled those junction boxes with silicon, and maybe there are a thousand other things I could have done in retrospect…

No issues with mold BTW, the relative humidity inside rarely reaches 50%.

Finally…… out of the ground.

25 08 2022
Hamish McGregor

Mike, thanks for the reply. You are correct that in retrospect there are a lot of things that could have been done, etc.

It is likely that water found its way under the retaining wall’s foundation and then a path to the (inside) joint between the slab and the inside of the wall.

Even the largest of French drains might have been overwhelmed if the surrounding infill is too porous (mulch) or lacks an impervious top-surface layer (clay under top soil, or hardscape) or the lack of any kind of slope away from the wall – in your photos above the pooled water and grass suggests an area flat as a pancake.

Hopefully you get an opportunity to address it and it goes away permanently.

25 08 2022

You’re not wrong about overwhelmed French drains. There are two parallel ones running down the driveway between us and the neighbour with the digger. They’re HUGE because they drain over half of the 25 acres above us and a substantial amount of Matt’s property too. There’s a slight rise on this driveway and the drain does a 90° turn into our dam. All this was done fifty years ago or more when it was a giant apple farm….. That drain was overwhelmed and water ran down the driveway towards our main road where it turned in front of our shed like a river! It’s no wonder Geeveston was flooded with that much water with nowhere to go….

25 08 2022
Blue Peter

G’day Mike, any chance of another cup of coffee @ DS’s?

What we “Humans” have done is unleashed a monster, it is now free to roam in the atmosphere.
There is NO longer any normal in the weather.
Does La Nina, El Nino even apply any more?
With in the next 5years I expect 1,000,000 of the state to be burnt.
Watch out for a FLASH DROUGHT.

In the meantime brace for impact,

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