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David Wilson Says

If it’s Flooded. Forget it!

There’s some serious drama unfolding as we speak in northern NSW and much of QLD at the moment as the elements unleashed by Cyclone Debbie play out their devastation. The ridiculous winds reported by the news services as the cyclone hit the coast were spectacular, but the rainfall is mind-boggling!

All that water has to go somewhere and so creeks and rivers run a banker, or in this case burst their banks and spill over into farmlands and ultimately towns, urban areas and cities. I feel for all those business owners watching their livelihoods disappear, the homeowners who’ll soon be sweeping mud from their homes and calling their insurance companies and worse, the families grieving for loved ones swept away in the turbulence. You see each time there’s a major deluge 4WD owners start taking chances crossing streams where it’s patently obvious there’s going to be trouble. Sadly a lot of them don’t come home.

So let’s get some facts about the dangers of 4WD use in water.

Firstly I hate crossing streams. I know 4WDs aren’t submarines and the risks in water too deep are great. I live in a State where big wet-weather events like this are rare, never happen, so my skillset for dealing with this type of activity is meagre. Even those who regularly cross streams will acknowledge that there are a lot of variables and that there’ll be days when it’s a gamble.

I learnt a lot from last year’s almost monthly downpours and especially the one that hit the east-coast on the 5th June. You’ll remember it, the one that swept that swimming pool away on the beach at Collaroy.

That event reached inland and the ACT got pummelled and sadly a Kambah local drowned after his DMAX was swept off a crossing on Paddy’s River Road under the Cotter Dam. There’s sad irony written all over this one. Within striking distance of the Stromlo SES depot and apparently whilst their daring rescue was being undertaken, the ute was flipped and he disappeared into the torrent. That would have been a gut-wrenching moment for the SES, so close and yet so far.

That’s one totalled D-MAX after wandering into a flooded creek. Sadly the driver didn’t survive.

Out of all this drama came so good, in the form of decent science courtesy of the University of NSW.

Engineers in the Water Research Laboratory tested the behaviours of passenger vehicles and 4WDs when they encounter flash floods and the results aren’t good news if you’re one to delve into a bit of water-borne adventure every now and again.

Flooding a giant tank in which a GU Patrol had been placed they discovered a couple of surprises, one that a 2.5 tonne full-size 4WD will float pretty easily.

Automotive engineers respond to we consumers demands for quiet vehicles with dust-free and climate-controlled interiors (although Editor Steane’s Defender tells me that he’s OK being able poke a finger through the gaps at the bottom of his doors), so they make a modern 4WD very air/watertight. All the nooks and crannies are sealed, all electrical cabling pass through grommets exiting doors and under-bonnet areas and ventilation flaps are sealed upon closure.

I think you can see where I’m going with this, as that bathtub filled up the Patrol became a tinny and the depths this started to occur were pretty insignificant.

Grantley Smith (Principal Engineer on the project) said “What was surprising was just how little water it took to make even a large vehicle unstable”. He went on to explain “they became vulnerable to slow moving floodwaters once the depth reached the floor of the vehicle. Even in low water depths and slow flood speeds, floodwaters had a powerful enough force to make them float away.”

Uni NSW tested vehicle flotation and bought an old GU Patrol to see what would happen. Well, at barely 450mm depth it was unstable and at 950mm it was a boat, totally afloat!

The Patrol became buoyant enough to become unstable at 450mm depth and that’s just above axle-height. At 950mm the vehicle was fully afloat, and like a tinny, able to be moved with the force of a hand. That height is around where the headlights sit, so if you’re used to seeing internet heroes ploughing through raging streams, I think you can see the disaster potential.

So now is NOT the time to take on that stream. If you’re late for work or an appointment going there the usual way probably won’t be possible, so yes you’ll be late for you’ll need to take the long way around if it exists? Perhaps better to cancel and find something more productive to do.

Think about what might happen if you pushed-on and like that poor soul from Kambah, you run out of steam mid-stream and there’s no fall-back position. The swift-water rescuers or the chopper folk are putting their lives on the line for you, so there’s more at stake than just yourself.

Remember – If it’s flooded. Forget it!

PS The QLD State Government has a great initiative advising of the dangers of crossing streams in flood and you’ll find that advice here

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