Henry C. Adams

Capitolo 48

rain-water in the sewers in Birmingham was brought out among
1900 and 1904 of the Mr. D. E. Lloyd-Davies, M.Inst.C. E., the
results of what you/he/she is published in Vol. CLXIV., Min Proc.
Inst.C.E. He showed that the quantity that reaches the sewer to some
point was proportional to the time of the concentration to that
point and the percentage of impermeable area in the district.
The time of the concentration had arrived to calculating the
time that rain-water would employ to flow through the
longer line of sewers from the extreme confinements of the
district to the point of observation, supposing the sewers to be
flowing half full;  and adding to the time so it got the
period forced for the rain to get in the sewers that
it had been varying for one minute where the roofs were directly connected
with the sewers to three minutes where the first rain had
flows along the street gutters. With a middle speed of 3 fts
per second the time of the concentration will be thirty minutes for
every mile of sewer. The total volume of rain-water that passes in
the sewers were found to bear the same relationship to the total one
volume of precipitation as the flow of maximum in the hole of sewers
to the intensity of maximum pluvius during one equal period to
the time of the concentration. He subsequently affirmed that while the
flows in the sewers it was proportional to the global rain
during the time of the concentration, it was directly also,
proportional to the impermeable area. Putting this in
figures, we see that in a district where the whole area is
impermeable, if a point is taken on the principal sewers that are this way
put that precipitation to the head of the sewer of branch
removed furthest employs ten minutes to arrive him/it, then the
flow of maximum of past of water of storm that stings it will be
you equalize above approximately to the total quantity of precipitation
the whole area of drainage during one period of ten minutes, and
further, that the pluvius total quantity that arrives the
sewers will approximately equalize the quantity fall total. If,