Experiment on vehicles crossing flooded waterways

[spot01]

An interesting study on the effect moving water and depth has on vehicles crossing waterways:

http://www.weatherzone.com.au/news/car-experiment-shows-extent-of-flood-danger/524452

[Dicko1]

As the adds keep saying in Qld....If its flooded, forget it. Yet we still get people swept away in cars during floods. Darwins way of keeping the nup-nups in check.

[Wazzap]

As the adds keep saying in Qld....If its flooded, forget it. Yet we still get people swept away in cars during floods. Darwins way of keeping the nup-nups in check.

We had some pretty bad weather in NSW last week, and so many people still tried to cross flooded roads. Had 3 people die when they/their cars were washed away, and so many people getting cars stuck in the flood waters because they thought they could get through (despite there being other cars stuck in the flood waters they were about to go through!).

[dhula]

Saw it on one of the morning shows this morning.
I thought it was pretty speccy to see the pootrol sitting in the tank with the water level at just below bonnet height and because the back end was floating, the two people in the tank with the car could push it around with little effort.

You'd think that most people would be well aware of the drama's flood waters can cause and that it's frikin' dangerous to try and drive through them, there having been heaps of rain on the east coast over the last couple of years or so, but alas it seams those that try to get through have the same mentality as those muppets on the road that just have to get there first come hell or high water.

[Lost1]

Just another Darwinian moment. No amount warnings can save some people from themselves.

[KiwiNTPajero]

people dont seem to be aware that a (relativley) enclosed vessel will float even if it will keep running.the big 4wd in some ways will be worse of cos they have a big volume to offset the big ger mass

[spot01]

Buoyancy

It is also worth noting that once the water is even just a bit above floor level, even though the vehicle may not be floating, it is gaining buoyancy & becoming lighter. As a result, there is less weight on the wheels & less traction - I suspect this is one reason why vehicles tend to get bogged in river beds more easily. Combine this with flowing water and .

[scribble88]

Thanks for sharing Spot01.

That was amazing to read.

I am a city slicker from WA, we don't get flooding like you eastern state-ers do. I wasn't aware of how little water it takes to move the car.

[Jasonmc73]

It is also worth noting that once the water is even just a bit above floor level, even though the vehicle may not be floating, it is gaining buoyancy & becoming lighter. As a result, there is less weight on the wheels & less traction - I suspect this is one reason why vehicles tend to get bogged in river beds more easily. Combine this with flowing water and .

Your theory makes total sense & also makes sense why tray back utes i've driven quite deep were fine, less buoyant back half of vehicle.

So that also makes sense why you see 4wd's in Cape York once the water is waist deep inside vehicle they tow out easier, they've become one with the elements

[old Jack]

Your theory makes total sense & also makes sense why tray back utes i've driven quite deep were fine, less buoyant back half of vehicle.

So that also makes sense why you see 4wd's in Cape York once the water is waist deep inside vehicle they tow out easier, they've become one with the elements

Not quite, Jaso.

Once there is water inside the vehicle buoyancy is lost and the vehicle can be move difficult to recover.
If the water level inside the vehicle is higher than the outside, and this can happen as you tow the vehicle out, the water trapped inside adds to the weight of the vehicle so it is a good idea to crack the doors open as the vehicle is recovered so the water can drain out.

A traytop also has the advantage of less side area down low so there is less side pressure on the vehicle if the water is flowing.

A cubic metre of water is 1000litres and 1000kg in weight.

Remember a snorkel does not turn your 4wd into a submarine, most modern cars will have their electrics/electronics drown before the engine ingest water. Often a snorkel can give you a false sense of security so you tackle deeper water crossings with less preparation. Once the water is deeper than 400mm or 500mm then it is best to fit blind to the front of the vehicle so water is not forced through the grille and radiators and into the engine bay. If the water is dirty then any water that is force through the radiators will leave a deposit of silt. This silt quick builds up and blocks the air channels of the radiator and will lead to overheating!

Those spectacular fast drives through dirty water for the classic "I am tough" photo can easily lead to overheating problems later.

OJ.

[Kingbrown]

Well said OJ.

On a Cape York trip last year I was surprised at how few people fitted a blind/bra for deep water crossings.

Being prepared for rapid recovery PRIOR to entering the water is also a must.

There's also the risk of the radiator fan being pushed through the radiator. A vehicle we came across at Gunshot was a case in point. A week later he was still stuck at Bramwell waiting for parts.

[erad]

OJ wrote " This silt quick builds up and blocks the air channels of the radiator and will lead to overheating!"

As usual, you are correct, but also even if you don't get enough mud to block the airflow, even having a layer of silt on the fins acts to insulate the fins and therefore reduces the cooling ability of the radiator.

[Jasonmc73]

Not quite, Jaso.

Once there is water inside the vehicle buoyancy is lost and the vehicle can be move difficult to recover.
If the water level inside the vehicle is higher than the outside, and this can happen as you tow the vehicle out, the water trapped inside adds to the weight of the vehicle so it is a good idea to crack the doors open as the vehicle is recovered so the water can drain out.

A traytop also has the advantage of less side area down low so there is less side pressure on the vehicle if the water is flowing.

A cubic metre of water is 1000litres and 1000kg in weight.

Remember a snorkel does not turn your 4wd into a submarine, most modern cars will have their electrics/electronics drown before the engine ingest water. Often a snorkel can give you a false sense of security so you tackle deeper water crossings with less preparation. Once the water is deeper than 400mm or 500mm then it is best to fit blind to the front of the vehicle so water is not forced through the grille and radiators and into the engine bay. If the water is dirty then any water that is force through the radiators will leave a deposit of silt. This silt quick builds up and blocks the air channels of the radiator and will lead to overheating!

Those spectacular fast drives through dirty water for the classic "I am tough" photo can easily lead to overheating problems later.

OJ.

OJ
You've taught me a lot & i'm very greatful

Yeah nah as far as deep water goes, i've taken note of previous conversations on forum & when wiring Pajero, fitting Automate i have a clear picture of the Canbus wiring system & all it's fine little wire friends that make it up
Including the Tranny ECU in front of passengers feet, engine ECU think up in one kick panel.
Also read the Pajero manual, wading depth ain't the parking depth, its in the book!

Once upon a time Diesel ute's & alike had pull stop for injector pump, I had one, waist deep no worries, park & have a picnic if you please.
I recall getting stuck in Petrol 2wd Rodeo/ Isuzu column shift in a lucky stone creek down around NSW border, drove it many times, car was full wet inside & parked there for maybe 45 minutes whilst we went & got farmer with tractor to pull out.
Open doors, vinyl floor, vinyl bench seat no problems

The modern motor vehicle is not this beast, i get it the pressure against side of vehicle etc.

My opinion of the Pajero as a submarine, yeah nah

I drove through dirty creek crossing last week must have been 200mm deep i reckon & i had a good look, didn't want to wet my toes though to make sure i was rite 1st before i tackled her

I have not enough coins to be a hero or the reason as to why, less testosterone than i once had as well.

[alanymarce]

We were held up for two days in Northern Kenya by a fast-flowing flood down a "river" which is normally just sand. Had a snorkel etc., but didn't try crossing - about a metre deep (not a problem) but fast current...



The only vehicle which tried was an Army LC and they did it (successfully) by loading it up with a group of bystanders, they probably had a dozen people on board.



We waited until the current had subsided, which also resulted in less water depth (0.4 m or so with one deeper hollow) and passed with no problem.



The sad news - further south, at another "river" a 'bus tried to cross, was swept away, and 17 people were lost.

[Scrambler]

We were held up for two days in Northern Kenya by a fast-flowing flood down a "river" which is normally just sand. Had a snorkel etc., but didn't try crossing - about a metre deep (not a problem) but fast current...

The only vehicle which tried was an Army LC and they did it (successfully) by loading it up with a group of bystanders, they probably had a dozen people on board.

We waited until the current had subsided, which also resulted in less water depth (0.4 m or so with one deeper hollow) and passed with no problem.

The sad news - further south, at another "river" a 'bus tried to cross, was swept away, and 17 people were lost.

Sounds like you were the smart people. If the LC had lost traction the ballast would have jumped: and how many lost or injured then?

Slow down or arrive dead on time, as they say.