Here we go again . . .

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

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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John Oxley Centre Fail

A plaque in the old courtyard of the John Oxley Centre, comemmorating Oxley's landing at Western Creek.

A plaque in the old courtyard of the John Oxley Centre, comemmorating Oxley’s landing at Western Creek.

Back in April 2012 I posted about the renovations of the big courtyard in between the two office towers of the John Oxley Centre on Coronation Drive. This courtyard sits more or less on top of the old stream of Western Creek (now Milton Drain) just before it met the river. It is quite likely where John Oxley came ashore in 1824 to look for fresh water, which he found in abundance somewhere along Western Creek.

In the gardens of the old courtyard there were plaques engraved with excerpts of John Oxley’s diary describing his landing here in 1824. I wondered if these might somehow survive the renovations, or if some other homage to Oxley’s landing might replace them.

The two 'signposts' at the entrance to the newly renovated John Oxley Centre.

The two ‘signposts’ at the entrance to the newly renovated John Oxley Centre.

Last weekend I finally got around to seeing how it has all turned out. The whole space has been given a facelift to give it a more ‘modern’ look and feel. (To my mind it was hardly worth it, but hey, that’s not my call to make.) The plaques are gone, but Oxley’s landing has not been forgotten. Unfortunately though, the effort to commemorate it could hardly be described as successful.

As you approach the courtyard from Coronation Drive, you might notice these two oddly shaped steel plates affixed to two intricately marked square poles. Or more accurately, there are four plates, each fixed to opposite sides of the poles to give the impression of two distinct shapes. What are they meant to be? Flags? Signposts? There is black trimming running around the outline of the plates, and also diagonally across them. On one of the plates, half of the diagonal line already appears to have fallen off, leaving a smear of glue. Is this supposed to be the outline of the river? The creek, perhaps?

Now, if you stand beneath the plates (they are about two and a half metres above the ground) and look closely, and if the light strikes them at just the right angle, you might just be able to see that there are letters embossed on them:

The two ... erm, 'pages' on the posts outside the John Oxley Centre.

The two … erm, ‘pages’ on the posts outside the John Oxley Centre.

Aha! This must be it! Sure enough, at the top of the two ‘skinny’ plates are the words “TUESDAY SEPTEMBER 28TH 1824” (all written in uppercase). The words continue, but reading them is a challenge because they are interrupted by the post and the black trimming running right through the middle of the ‘page’ (ahhh… so perhaps the shape is meant suggest a scrappy page out of Oxley’s diary!?). They run something like this:

A CALM … NIGHT
LANDING A…T THREE
QUARTERS…MILE FROM
OUR SLEE… PLACE.
TO LOOK…WATER,
WHICH WE…UND IN
NDANC…ND OF
…ALITY.
BEIN…S SEASON
A CHAIN…ONDS
WATERING…VALLEY

Eventually it culminates at the famous reference to a “FIRST SETTLEME…P THE RIVER”.

I knew what I was looking for. I visited the place with the specific aim of seeing how Oxley’s diary had been reflected in the new courtyard. I only noticed these posts because I was looking for something, and I only noticed that there was writing on them because I was looking for that too. And had I not already been familiar with this particular diary entry, I wouldn’t have had the foggiest idea what the words were trying to say, or where they came from.

So much for the skinny post. What about the fat one with the river running across it? I don’t even know. Even by zooming in on my photo I can only read half of it. Maybe it’s another page from Oxley’s diary. Or maybe it’s from another document describing the area. As far as I could tell, there was nothing to provide an explanation (perhaps I just didn’t look hard enough).

I honestly can’t view this installation as anything other than a dismal failure. It accomplishes virtually nothing, except to cause confusion to anyone who happens to notice it in the first place. If someone unfamiliar with the story of Oxley’s landing can look at it and deduce something about the history of this site, and the reason for the building’s name, then I take my hat off to them.

Or have I missed something?

Milton Drain’s tidal limits

Last Saturday (the 12th of January) we had a particularly high tide. According to willyweather.com, high tide at the Port Office was 2.7m at 10:51am. The Bureau of Meteorology’s tide tables suggest that we won’t get another tide this big (give or take a few centimetres) until the 26th of May.

Tides at the Brisbane Port Office for the week of 8 January 2013, according to willyweather.com.

Tides at the Brisbane Port Office for the week of 8 January 2013, according to willyweather.com.

I was aware of this only because a couple of weeks earlier I had passed by the Milton Drain and noticed that it was unusually full. When I looked up the tide tables to see how that tide rated, I found that an even higher one was coming. So I made a point of visiting the drain at high tide on the 12th of January. I even put a reminder in my phone. Yes, this is the sort of thing that I do.

Here is what I saw:

Milton Drain at high tide on 12 January 2013.

Milton Drain at high tide on 12 January 2013.

The water level must have been barely half a metre below Milton Road. At the other end of Milton Park, the water was just a few centimetres from the top of the concrete:

Milton Drain at high tide on 12 January 2013.

Milton Drain at high tide on 12 January 2013.

Milton Drain at high tide on 12 January 2013.

Milton Drain at high tide on 12 January 2013.

Not much room to move, is there?

I’m not sure how much higher the tides get than this; I’ve never studied them before. Next January, BoM’s tide tables predict a tide about 10cm higher than this one, and the maximum last year was just as high. So it looks like Milton Drain is built more or less exactly to the height of the highest high tide that typically occurs. This is all well and good, unless of course there happens to be stormwater flowing through the drain as well. If a tide like this coincided with heavy local rain, the drain would spill over into Milton Park (as I’m sure it has on many an occasion). And if the river is already swollen from rain further upstream — well, we know what happens then.

What I didn’t think to do was to see if the water was visible through any of the drains in Gregory Park or even Rosalie, as a tide like this would have surely reached that far. I did, however, get down to the river later that afternoon, and saw clear signs that the water had spilled over onto the bike track just downstream of the old floating restaurant. But I didn’t have my camera with me. Perhaps in May . . .

Floods aniversary special

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