Tag: floods

Too many 1-in-100-year floods

A conversation

In the wake of our 2025 floods (Jan 28 – Feb 12), North Queensland Conservation Council posted a call to action on facebook. I agreed with it and then tried to say why the “1-in-100-year event” label has become so obviously misleading.

NQCC: Floods and heatwaves are the new normal.
North Queensland has been hit hard again, and these so-called “1-in-100-year events” are happening way too often. Climate change is making extreme weather more frequent and intense, yet our leaders still aren’t taking the urgent action we need. …

Malcolm Tattersall: “1-in-100-years” is a (sort of) average and what it really means is that there is one chance in one hundred of such a flood occurring in any given year. But that measure is purely statistical and historical. As such, it relies on the future being like the past, and climate change has completely undermined its validity.
The calculation is really very simple – too simple, in fact, to include any of the changes (e.g. urbanisation, dam construction, climate change) which might make nonsense of the prediction.

That was enough for facebook but pursuing the science further seems worthwhile.
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Townsville floodways

Townsville is built on a floodplain. From a distance the whole city looks flat, with a few very obvious bumps: Mt Stuart and its foothills, Castle Hill and Mt Louisa. But the flat area is not quite flat.

Early settlers built on the (slightly) higher areas, avoiding the mudflats and mangroves, and formed their roads on the (low) ridges, leaving the (shallow) gullies and creeks alone. Over the 150 years since, low spots have been built up, and watercourses deepened and straightened, as urbanisation encroached on the lower ground. But the natural drainage network persists, as we realise (often unhappily) whenever we get a lot of rain.

An overview
Map of Townsville watercourses
Townsville watercourses, Castle Hill to Mundingburra

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Townsville’s 1925 floods

Someone shared a Townsville flood photo on social media a few days ago and I saved it for potential recycling. Then the rain started and everyone shared a flood photo on social media.

This is now more topical than it was when I saved it.

historic photo of flooded city
Ross Creek, looking upstream

I have just spent a few minutes on gooooglemaps to produce a 3D rendering from approximately the same location, somewhere up on Melton Terrace or Willmett St.

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Off-grid but not by choice

Power blackouts can happen any time. When they do, we have to do the best we can with what we’ve got, and this post is mainly about using a camping fridge, power station and PV blanket, as described in my previous post, to keep ourselves safer and more comfortable off-grid.

If we have PV solar and a home battery that we can use off-grid, we’re fine. (They are not common, though.) Or if we have an EV with V2L (vehicle to load) capability (not common either), all we need is an extension lead. If we haven’t, here’s a plan.

But first, some useful basic emergency information

Power outages that are long enough to be problematic are usually due to cyclones and floods, so these key sources of safety information are worth noting. For the Townsville area:

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The last of the Wet

I have noticed before that our Wet seasons can end with a farewell deluge. If what we’re getting now – 200 mm and more in a day or two – is this year’s example, it’s a bit late.

John Anderson, veteran rural reporter for our local paper, reckons that if we haven’t had rain before Anzac Day, we’re not getting any. My own rule of thumb was that Easter marked the end of the Wet season, and I suspected that it might be tied somehow to the lunar and solar calendars. Easter, after all, falls just after the first full moon after the Equinox (more detail here).

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