Tag Archives: floods

Here we go again . . .

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I don’t know about you, but I didn’t expect to be seeing scenes like these just a couple of years after January 2011. (See the new Gallery page for more pictures of today’s flooding.)

Gregory Park, 28 January 2013. The tide was still rising, and water was gushing into the park through this drain.

Gregory Park, 28 January 2013. The tide was still rising, and water was gushing into the park through this drain.

Milton Drain, from the mystery building on Milton Park, 28 January 2013.

Milton Drain, from the mystery building on Milton Park, 28 January 2013.

Then again, we shouldn’t be surprised: there’s no reason why floods should be spaced out evenly over time. Indeed, the historical record of Brisbane’s floods suggests that they often come in twos or threes.

Flood events greater than 1.7m in the Brisbane River since 1841. Also shown are the estimated mitigating impacts of river works and the two dams. All data sourced from the Brisbane River Flood Study except the effect of the two dams, which is indicative only and has been inferred from an analysis on page 523 of the final report of the Flood Commission of Inquiry.

Flood events greater than 1.7m in the Brisbane River since 1841. Also shown are the estimated mitigating impacts of river works and the two dams. All data sourced from the Brisbane River Flood Study except the effect of the two dams, which is indicative only and has been inferred from an analysis on page 523 of the final report of the Flood Commission of Inquiry.

Meanwhile, just downstream . . .

A duckbill valve on the riverbank at Milton

A duckbill valve on the riverbank at Milton

I’m also guessing that the Brisbane City Council wasn’t expecting their new backflow prevention devices to be put to use so soon. As explained in my essay Backflow to the Future, the Council has recently installed duckbill valves and flap-gates to prevent flooding in several locations, including the Cribb Street drainage system in Milton. This area spans between Cribb Street and Park Road.

After my little adventure this morning I took a walk around this area and could see no evidence of flooding. Unless this whole area is higher up than the Western Creek area (which I do not believe to be the case), this means that the duckbills and flap-gates are doing their job.

If this is the case then the Council can give itself a pat on the back. And if it has any sense, the Council will look for ways to tell everyone how many properties these devices saved from being flooded. Then again, the Council may not want to create too much work for itself. Before long, every suburb in Brisbane will be wanting one of these duckbill thingies . . .

When waters collide

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Just over a week ago I posted about the ‘tidal limits’ of Milton Drain, noting that at a very high tide, the drain is pretty much full to the brim.

Today, I braved weather that ranged between miserable and awful in order to see how the drain held up when it had more than just a high tide to contend with. With the remnants of Cyclone Oswald looming over South East Queensland, Seqwater began releasing water from Wivenhoe Dam on Friday evening, and according to the Seqwater website, the releases are expected to continue for several days. So we have the tides coming in from downstream, the dam releases coming from upstream, and the stormwater from the Western Creek catchment racing through the drains towards the river. What happens when the waters collide?
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Floods aniversary special

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Two years ago today, Rosalie and many other parts of Brisbane were underwater. Any misconceptions we had about the power of Wivenhoe Dam to save us from ever being flooded again were swept away, and before long, attention turned to what, if anything, we could do to stop this from happening again.

In a post in The Forum (actually the first!), a visitor named Barry noted that the Council plans to install a floodgate at the mouth of Western Creek (Milton Drain) to mitigate future flooding in Milton and Auchenflower. As in many other parts of Brisbane in January 2011, the floodwaters that inundated the Western Creek catchment did not spill over the riverbanks, but entered instead via the stormwater drains that discharge to the river. The diagram below, taken from the Council’s fact sheet on backflow flooding, illustrates how this kind of flooding occurs.

Concept diagram of backflow flooding, taken from the Brisbane City Council's <a href="http://www.brisbane.qld.gov.au/downloads/environment_waste/water/Backflow%20Fact%20Sheet%20June%202012.pdf">factsheet</a>.

Concept diagram of backflow flooding, taken from the Brisbane City Council’s factsheet.

The Council has indeed stepped up to the plate and has already started building backflow prevention devices in Milton and elsewhere. And among the areas that have been flagged for future attention is the mouth of Western Creek.

This is a laudable idea, but the Council can hardly claim credit for it. The idea of using floodgates to protect Milton and Rosalie has been doing the rounds for over a century. In a new page entitled Backflow to the Future, or: How we learned to stop worrying and love the floods, I present a retrospective of these past proposals, courtesy of newspaper clippings from The Brisbane Courier and The Courier Mail that I have found while trawling through Trove.

The title of the essay is strictly tongue-in-cheek, and I’ll admit, downright cheeky. I’m not suggesting for a minute that we really enjoy the floods, and I don’t want to offend anyone who has suffered from them. But I do hope to put into stark focus the question of why, after all these years, we have not adopted such simple measures as floodgates to ease the pain. And I confess, the temptation to structure an essay around Dr Strangelove was just too much for me to resist.

I hope you enjoy the new page. It has been a fascinating journey to write.

-Angus

Fun with maps

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Western Creek as depicted on a map from 1859 (Queensland State Archives Item ID620656) overlaid on an aerial photograph of the January 2011 flood (Department of Natural Resouces & Mines)

Western Creek as depicted on a map from 1859 overlaid on an aerial photograph of the January 2011 flood

The banner at the top of this page features a depiction of Western Creek from A.R. McKellar’s 1895 map of Brisbane overlaid onto the modern suburban landscape. For me this captured the essence of what the site is about: gaining a deeper understanding the modern landscape though an exploration of its past. This graphic served its purpose, but I always knew that it was just a prototype for what could be achieved on a grander scale.

Now that I’ve collected a few more old maps, and discovered the free aerial photos taken during the 2011 flood (available from the Queensland Government Information Service), I have started to put the two together, and you can see the results on this hastily assembled new page: The lost creeks rise again. That page looks at how the floodzones from January 2011 in Milton and Auchenflower coincided with the location of old creeks, swamps and lagoons that have long been drained and buried. The image to the right (click to enlarge), which shows Western Creek between the river and Gregory Park, is one example.

What you won’t find on that page is the image below, which shows the CBD area overlaid with a plan of Brisbane from 1843. There wasn’t much to Brisbane at that stage (it had only just ceased being a penal colony), but in addition to the few buildings and roads marked, there are some fascinating natural features on this map. For example, notice the creek that begins up in Spring Hill and flows down towards a small dam which is right on top of where the new law courts are today. This was Brisbane’s first water supply. The stream continues through a small pool at King George Square and flows to the river near Creek Street. Click here to see this part of the map in a bit more detail.

A plan of the town limits from 1843 overlaiad on an aerial photo from January 2011.

A plan of the town limits from 1843 overlaid on an aerial photo (Dept of Natural Resources and Mines) from January 2011.

Across the river, nothing is marked in South Brisbane except for a creek that winds through the Convention Centre and Southbank Parklands (where there are now artificial streams). This enlargement shows the area in more detail.

I plan to use images like this wherever I can in future pages on this site, so stay tuned for more in the near future. What I’d really love to see is this done for as many old maps as possible, and the results made publicly available as files that can be imported into GIS software, or even via platforms like Google Maps or NearMap. Combined with historical aerial photographs as well, it would be an absolute treasure trove for professional and armchair researchers alike. So, anyone got some funds?