My little girl is 7 and just isn’t wrapping her head around this and I need to find a better way to explain this.
She is so so smart because she saw the coverage of Helene, and heard 17″ and hot confused.
I told her the water runs from the high places to the low places, but then she asked why the water doesn’t leave the low places and why is it still flooded.
I’m bad at dumbing things down.
In: Planetary Science
So it falls 17″ everywhere. All of this is going towards rivers (both above ground and underground. Usually a lot more water is transported underground through ground water, though these flows are a bit slower than water above ground. This is why rivers keep flowing when it hasn’t rained recently. There is still more water in underground reserves that haven’t been able to drain yet).
When these underground flows are being overloaded it starts to flow above ground. In hilly terrain this excess above ground water will quickly find its way to low ground, and this low ground gets water from ALL of the surrounding area uphill.
This water will try to find a river to flow to. But if the river is normally 3 meters deep and it’s now 1 meter taller than normal, that’s only 25% more flow than normal (ok, a little bit more since it’s usually flowing faster) but there is just so much water than rivers can handle and the groundwaters ability to soak up this water is overloaded.
It’s kind of like dropping a big ass bucket of water into your sink, it’s going to take a while to empty out even if the drain isn’t plugged.
A more accurate analogy would be if you put a lot of sponges to form an uneven covering a very slightly sloping half-pipe (simulating ground waters ability to absorb rainwater) and then dropped bucket after bucket of water in from the top. To some point the water is just going to soak up into the sponges, then get pushed downwards by gravity and it’s going to slowly drain from the bottom. That’s how a river normally works. Draining the water that’s slowly seeping out of the ground into a pipe at the lowest point. But pour down enough water and it will flow over the top, but it’s going to keep getting trapped in the “uneven parts”, which is where you get floodings and standing water.
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