I don’t get how houses/buildings can go under water?
In: 8
Imagine a bath or sink/basin.
If you turn the tap on, and the water is flowing in faster than the drain allows it to drain out, it will fill up. If you leave it like that for a while, eventually it will overflow. That’s a flood.
When the incoming water is sustained for a while and overwhelms the ability to drain (into the soil, downstream, etc.) then it will start to build up. If that continues for hours or days, eventually the river, etc. will overflow.
Rivers tend to occur on rocks etc. that *don’t* absorb water (are not porous) because otherwise they wouldn’t form a river in the first place, the water would just drain away. Natural rivers tend to form on non-porous rock, which means that the water can’t drain into the landscape and can only go “downstream”. But there’s a limit at which the surrounding soil/rock can contain it, and places that get flooded tend to have non-porous underpinnings and/or are lower than the river (so when it “spills over” from the non-porous rock that normally contains it, it goes downhill to the areas that get flooded instead of going downstream).
Plus, if you have a serious storm, the sheer volume of water means the river can be handling something like 5-10 times the normal amount of water in it… so it wants to “become” wider and deeper anyway and floods floodplains – those places near a river which are naturally where the water will flow if the river overflows.
If you multiply the size of water in the river, it’s not going to flow downstream in the same way at all… it’s going to find every little nook, cranny, come over the top of the riverbanks, and find a new way down to the sea… through the town if that’s the way gravity takes it.
It’s like having a gutter drain that the water normally streams down, then putting ten times the amount of water down it. It’s not going to flow down the gutter, it’s going to spill out over the sides and go anywhere it likes.
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