Flood zone/prone areas in Canberra

miz said :

The land where Hindmarsh want to build at Woden (and where the police station is, too) was awash in the 1971 flood. They are stark raving bonkers to be wanting to build on that land.

I have been told that the big cement drain didn’t exist in 1971, the drain was installed due to what happened just down the road.

On a side note, I learnt at school that Kambah has been designed with floods in mind. Most parklands in Kambah have some sort of a dry creek bed in them. When the street storm water drains can no longer cope with the intake, the water flows to these creek beds. Those creek beds lead to huge drain openings, which are around 1.5 cubic meter in size & lead to huge 2 metre high drains. When those drains can no longer cope, the water then flows through the series of sports fields via the underpasses & over Drakeford Drive (near Kambah School). This is why Kambah’s underpasses have rocky beds in the middle (to slow the water down). The worst case was for water to pool on the former oval of Kambah High School, which is now covered in buildings for Kambah School, the water then flows past Jenke Circuit to Lake Tuggeranong & then (if the dam wall survive) over Lake Tuggeranong spillway & down Tuggeranong Creek to the Murrumbidgee River, to flow through Kambah Pool (to say one more goodbye to Kambah.

I am open to corrections on this plan.

The land where Hindmarsh want to build at Woden (and where the police station is, too) was awash in the 1971 flood. They are stark raving bonkers to be wanting to build on that land.

I don’t think that’s true about LBG and the John Gorton Building, tommy. It may be flooded from else ware but I don’t think the lake will get that high. Anything up to and including a 20yr flood there will be no perceptible difference to the water height on the lake, thanks to the gates on Scrivener Dam. During a 100yr flood, the water level will rise by about 1.5m from where it normally sits. Basically Water’s Edge may get a little wet but not much else will.

Sunshine, Duffy is a bit of a basket case. Like I said, it’s largely to do with the original design of the place. The fact that the same houses are getting flooded after remedial works have been carried out could be to do with the staging. Maybe for those improvements to work properly they need the downstream system to be upgraded as well and that just hasn’t been done yet. On the other hand, they could have just stuffed up and got the design wrong. Either way, I’d let ACTPLA know if I were you. By the way, the oval in Duffy is supposed to be a lake in times of heavy rain. It’s called a “detention basin” and helps reduce the severity of the flood downstream. It sounds like it was doing what it was designed to do.

mt ainslie, with a load of gopher wood..?

A few years back there were several hail storms which caused flash flooding as hail blocked normal drainage – the Tuggers one and then the massive Civic one. ACT Govt (very appropriately) listened to resident issues and sent out engineers to investigate.

They divided up the severity to Extreme, High, Medium and Low.

They have not yet completed the Extreme issues – I’ve got an issue rated High (I got an update last month).

Of course, there’s the basic Lake BG issue – when I used to be an APS, we built a data centre in the basement of the John Gorton Building where we were told that it’d only be affected in a 1/100 year flood.

I don’t think it’s a care factor issue for insurance companies in Canberra – they just get you with NC discounts and excess hikes. They didn’t bat an eyelid for our two “flood” claims.

@10… when Ginninderra Creek broke its banks around Macgregor last month it looked like another half metre or so would have led to some of the house along the creek getting some water lapping at them… but those houses were off streets like Berne Pl or Skirving Pl, not Kirkland, which is a fair bit higher up.

MacGregor – some Places off Kirkland Crt from memory. Very early 80s – some houses along the creek got a little wet or at least the water got very close.

Probably been seen to long ago and was, I think, pre Lake Ginninderra.

There is a topo map, somewhere, with the 100 year flood level for Canberra, showing how high it would get. It’s based around a normal waterways flood, not isolated flash flooding.

I sometimes get a little bit nervous because we’re close-ish to the Sullivans Creek storm water system, but after the heavy rain in early December and seeing how high the water got then, I figure we’d need a lot more water to put our house under threat.

Fingers crossed. I think being flooded would be horrible! 🙁

unfortunately they didn’t fix Duffy too well as exactly the same problems/flooding occurred a couple of weeks ago with the major storms we had. The same houses were flooded, the oval was a lake, roads buckled and cracked etc….wasn’t a pleasant experience for any of us

Geetee, you’re right about Duffy.

I think you’ll find that the government has undertaken quite a bit of civil works in Duffy to try to fix the problems there. As it turns out, many of the problems experienced are the result of poor detail design rather than poor planning and controls. Which is why it is able to be fixed without too much fuss.

Very interesting BB – thanks for that

I recommend looking at the last few months of Canberra’s 4th wettest year on record. Anything that went underwater is prone to flooding, don’t build there, and avoid it if it is raining heavily.

Duffy had some minor flooding a few years back. Nothing like Qld of course.

The 1971 flood was almost what we call a PMF (Probable Maximum Flood), think of it as a 1 in 100,000 yr flood. Also, it was very geographically isolated. Basically it was a freak event, a sad and tragic freak event.

All new dwellings must be out of the 100yr flood levels. That’s everything from flash floods where the drainage system can’t cope (built for a 5yr storm in residential areas) and the roads act like waterways, to major regional flooding of the creeks and rivers where it buckets down for days.

This has been the case for many years. You can safely say that pretty much all buildings in Canberra are free of the level of flooding you would expect to see on average once every 100 years. If anyone believes that this is not the case for their area, such as seeing minor flooding when no one else in the area does, contact ACTPLA and they will assess it. They spend millions every year fixing, upgrading and maintaining the stormwater infrastructure and flood controls.

Of course, that doesn’t include very local flooding, such as your backyard trying to drain through your house. This is not the government’s problem, it’s yours.

While the modelling and planning controls include a factor of safety, you can never make anywhere 100% flood proof. Somewhere along the line, someone has decided that to protect against anything more than a 100yr flood would be too costly, and so rare an event, that it is cheaper for society as a whole just to let the flood happen and pay for the cleanup later, even if that means a loss of life. People say you can’t put a price on life, engineers do it every day.

Canberra from the very start did not build in flood prone areas, as opposed to some of our neighbours who will not be named. The main reason that Lake Burly Griffin exists is because it is on a flood plain, it was always going to be left undeveloped, so why not make the area into a lake?

Most of our green space is actually floodway and many of our playing fields are flood detention basins, holding the water back and reducing the amount of flooding downstream. Don’t underestimate how much land and money has gone into reducing the likelihood of flooding in Canberra.

In answer to your question, I think insurance companies also rely on the 100yr flood principal. So I would imagine that it is very unlikely that anyone in Canberra wouldn’t be covered for flood. I would be very interested if someone could prove me wrong however.

Axeman – 1971 saw Woden hit by a flash flood which killed seven people.
http://en.wikipedia.org/wiki/1971_Canberra_flood.

I would think any low lying areas of Canberra have the potential to flash flood. Those big open flood channels around the place are not there for nothing. The large catchment areas and hills which make up Canberra can channel a lot of water. On the other hand its unlikely that Canberra would see large inundation from rising rivers like currently in Queensland.