6 January 2011

Flood zone/prone areas in Canberra

| The Axe Man
Join the conversation
27

Hi All,

With the recent goings up north with the flood I got to thinking if Canberra had an flood prone areas. I had a quick search online and at the ACTPLA website but couldn’t garner much information.

It’s probably not too bad an idea to know if there are any flood prone areas so people can check their insurance if they are covered for it or not. I can’t remember if Canberra has had any serious flooding or not either so I may already know the answer to the question, just thought I’d check

So, does anyone know?

Join the conversation

27
All Comments
  • All Comments
  • Website Comments
LatestOldest

SammyLivesHere said :

Chip, liked your explanation… actually when the storm went over the inner south yesterday it was all in play…. the roads were clearing, but the stormwater running between all the houses in my block was not working. Basically as you say, the water was coming down into the pipes too fast and the pipes could not take it – so instead of getting down to the lake under Adelaide Ave it was back-filling into the back garden – with no where for the water from the roof or the ground (I’ve got garden), and it coming back up the drains in the block (about 30 houses) – I was grateful the rain eased – allowing the water downstream to clear… but I wish they would open those Flood Gates at the Dam today, the ground is very wet and the lake is rising making it harder for the storm water drains to empty into the lake. why does it happen that the heavy thunderstorms come on w/ends and after 3pm? mmm

It sounds like you live in that low lying area in Deakin, possibly even where those newer houses were built a few years ago adjoining Adelaide Avenue (off Newdegate St) I think. If so, I can sympathise. I was very surprised and puzzled when they were built as I had always thought that was a floodway there. I have often wondered as I drive or cycle past how the developers managed or redirected the stormwater.

I had assumed also that the recent roadworks to and either side of Adelaide Avenue in that area was to assist stormwater underneath Adelaide Avenue. From what you say it sounds like those works haven’t helped enough if at all.

A few years ago I was part of a group that was instrumental in bringing the Woden floods of 71 to the attention of Stanhope – with myself and a gentleman from the South Coast (Name intentionally suppressed) efforts being rewarded with a proper memorial….

More info here – here and here

My mother lost a childhood friend in the floods, and that was partially why I was so passionate about a memorial.

There exists a facebook group still, but I am the sole member :/

From what I understand, there was a lot of cement around on what used to be a flood plain, and the drainage was such that the 3ft RCP that went under the intersection of yarra glen and Melrose was inadequate for the flow that day and became blocked with derbis, resulting in vehicles being washed away…As I understand, where the Athlon/Melrose intersection now lies was where some of the victims were found.

SammyLivesHere8:21 pm 18 Feb 12

Chip said :

There has been a lot of planning go into making Canberra flood resistant but Murphy’s law can be very cunning. Flash flooding in well planned undulating landscapes such as Canberra’s is often due to a very rare coincidence of incidents.

For example, if a storm front moves down a catchment at the same pace as the water moves along then the ability of a long catchment to cope with drainage is greatly reduced. If there are also cars, trees and hail blocking water in large drains then it gets heaps worse. If dam gates remain closed due to malfunction or an emergency downstream then it gets even worse for houses in lower areas in a local catchment that feeds into a lake or dam.

It is not cost effective to be able to cater for incredibly rare bad luck so infrastructure maintenance and vigilance and commonsense by government and residents is essential.

Chip, liked your explanation… actually when the storm went over the inner south yesterday it was all in play…. the roads were clearing, but the stormwater running between all the houses in my block was not working. Basically as you say, the water was coming down into the pipes too fast and the pipes could not take it – so instead of getting down to the lake under Adelaide Ave it was back-filling into the back garden – with no where for the water from the roof or the ground (I’ve got garden), and it coming back up the drains in the block (about 30 houses) – I was grateful the rain eased – allowing the water downstream to clear… but I wish they would open those Flood Gates at the Dam today, the ground is very wet and the lake is rising making it harder for the storm water drains to empty into the lake. why does it happen that the heavy thunderstorms come on w/ends and after 3pm? mmm

My back yard has not resided in months fence has rotted. Grass is thigh high in a few days post mowing

There has been a lot of planning go into making Canberra flood resistant but Murphy’s law can be very cunning. Flash flooding in well planned undulating landscapes such as Canberra’s is often due to a very rare coincidence of incidents.

For example, if a storm front moves down a catchment at the same pace as the water moves along then the ability of a long catchment to cope with drainage is greatly reduced. If there are also cars, trees and hail blocking water in large drains then it gets heaps worse. If dam gates remain closed due to malfunction or an emergency downstream then it gets even worse for houses in lower areas in a local catchment that feeds into a lake or dam.

It is not cost effective to be able to cater for incredibly rare bad luck so infrastructure maintenance and vigilance and commonsense by government and residents is essential.

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.

Have a look at Callam offices *(the grey concrete spaceship looking building near the Helenic club) when you are down that way, it was built over the concrete drain and the floor level didn’t start till well above the 100 year flood level for exactly that reason.

the round-about in a more minor form I think was there in the 80’s if I remember correctly from when I rode that way to the lake on the bike paths.

Comic_and_Gamer_Nerd6:44 am 18 Feb 12

huh? i have been living in duffy for ten years but dont remeber any flooding?

SammyLivesHere10:57 pm 17 Feb 12

I think you have to be very careful how you say things. In Canberra it is unlikely residents would suffer a flood event… although some Yarralumla residents are within the 100-year flood line. Most damage in Canberra is caused by Stormwater drain ‘run-off’… ie. the amount of redevelopment in the suburbs is happening much faster than the replacement of old infrastructure – fence to fence housing; and no or little gardens (with more hard-stand) – is causing at least 50 residents in Canberra to don their wet-weather gear and have some form of ‘storm plan’ in place… it is not uncommon for these residents to suffer water in their homes from flash flooding from the road – not through the roof. I agree with the guy who said building units over the Woden Stormwater drain is terrible… why did they do that? This is what happens in suburbs in storms in Canberra… this is not a ‘film’ this is the actual event… this one is now fixed, as BB said – after much canvassing and video’g and enduring six home floods and replacing carpets, furniture and enduring 12-months of hell – YES ACT Government will ‘act’… but let me tell you – you have to keep at it 7-days a week for 3-years… to get it fixed.. so next time you drive down a low part of the suburb think of the people who bought their house not knowing the ACT Government’s infrastructure was failing… as the Surveyor only checks the ‘block’ not the ‘suburb’.. and do your neighbours a favour – if your garage or garden floods – report it – that creates a history and could help a neighbour who is suffering internal run-off to get help much quicker!!!!! http://youtu.be/FpIH8DEkDwY

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’ve been wondering about that too.

TP 3000 said :

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.

Just looked this up on Wikipedia and the EMA database (http://www.disasters.ema.gov.au/Browse%20Details/DisasterEventDetails.aspx?DisasterEventID=1370). The concrete drain (a.k.a. Yarralumla Creek) did exist in 1971. The flooding of Yarra Glen occurred because debris blocked the drain and caused the flood to engulf the road. What I’m unsure of is whether the roundabout at Yarra Glen/Yamba Drive/Melrose Drive (as we know it today) existed then or whether Yarralumla Creek was closer to the road surface. (Wikipedia refers to a low level crossing at this intersection and I wouldn’t describe it that way now.)

diddler said :

my AAMI policy states it does not cover for flood but storm inundation. So from what I gather if the creek next to me spills into my house No cover , but if my gutters or driveway flood into the house I am covered

Correct. Most insurance policies will cover you for storm damage but not for rising flood waters.
ie. The people in Queensland are F*cked.

If a flood is meant to be heading your way, it may be advantageous to remove a few tiles on your roof and let it collapse before the flood waters get there. Just an idea.

my AAMI policy states it does not cover for flood but storm inundation. So from what I gather if the creek next to me spills into my house No cover , but if my gutters or driveway flood into the house I am covered

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.

Holden Caulfield5:22 pm 06 Jan 11

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.

Daily Digest

Want the best Canberra news delivered daily? Every day we package the most popular Riotact stories and send them straight to your inbox. Sign-up now for trusted local news that will never be behind a paywall.

By submitting your email address you are agreeing to Region Group's terms and conditions and privacy policy.