Assuming a constant 1 metre head of water, feeding a 7 metre long 35mm internal diameter pipe, what would the litres per minute flow be?
What would be a reasonable assumption for a maximum rainfall over 1 metre square in the UK.
Just curious because the above temporary pipe seemed to cope admirably with an extremely heavy down pour onto a flat roofed area of 10m x 4m.
Its rare to experience more than an inch or so..2-3inches is 'torrential'.
I believe the record for a single period or rain is the Indian Monsoon, where as much as 25" in a single shower has been recorded.
40 sq meters by 25mm would be 1 cubic meter or 1000 litres.You can empty a 1000 liter tank through 35mm pipe in a few minutes..
In that case I might leave it as a more permanent installation. The
35mm pipe was put in as a temporary solution lots of years ago. The roof drained to a water butt acting as a buffer, with an overspill going into the 35mm pipe.
Depends where you are in the UK, the SE doesn't appear to get much at all... 9" in a single month is par for the course for us. But looking at the rest of the post you really want to know the maximum rate not how much an area gets.
That band of rain that swept up the country today came through here just before 2100, max rate of 29mm/hr, but didn't last long just a few minutes, that is common. 50mm/hr is pretty heavy is happens a couple of times a year. A normal prolonged period of rain will tick along at 6mm/hr or less.
When I worked in Cumbria I remember one thunderstorm that was off the rainguage for 20 minutes, which had an FSD of 200mm per hour. We were /not/ in Seathwaite, but not too far from there.
Aye, and there's the rub. Floods in e.g. Lymmouth etc are due to intense storms that can drop several INCHES in a couple of hours, These are very rare, but...now and again, thats what happens..rain tends to be very unpredictable.
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