From about the middle of December 2010 until the end of January 2011, large parts of South Africa experienced more rain then it's infrastructure could handle and severe flooding ensued.
During the week of 6 January 2011, the Vaal, Bloemhof, Gariep and Vanderkloof dams rose to 105.5%, 101%, 109.8% and 105.8% of their respective capacities . Now percentages aren't a good measure of volume, so take a look at each Wikipedia page I've linked to for each to get an idea of just how much water this is. This is a lot of water.
As can be expected, the powers that be took full advantage of the sluice gates on the dams to prevent them becoming damaged but at the same time to control the flow of the river itself to minimize the damage.
At it's peak, the Bloemhof Dam's outflow was 2800m³/s. This is a lot of water and flowing at one heck of a pace. How how fast? Well, let me allow Danie van der Spuy, a specialist engineer in flood studies, put it in a manner you can picture...
Van der Spuy said that to get an understanding of the amount of water going through the dam's sluice gates one should think in terms of elephants passing in front of your eyes at any given second.
The average African elephant weighs in at 4.6 tons.
With 2 800m³/s flowing through the gates at the Bloemhof at the flood peak, one would have seen 609 elephants every second.
— News 24
Yes folks, elephants per second. A brand new unit of flow. Picturing a cubic metre is quite hard, especially if you've never seen one, but an elephant... that's a whole different story. And remember, these are African elephants; not those weeny Indian elephants ;-)
I quite like this explanation, though I doubt it'll become an SI unit anytime soon :-) .