Rainfall data for the design of sewer detention basins

2
i Hi cal
In t catchment the ins were igned for the 100 la
est his ca 1 storms for each outflow 1 eve 1 found through
screeni
1 rainfall es described in ion 2.2
Since many storms were the same for the different outflow
s total number of storms were reduced to 176 These 176
were rst run through the CTH-Model and the inflows to
sins for all storms were stored on a computer le That
fi 1 e was u for the design of the basins for different
outflow s Thus, the runoff for the different storms for
ba in needed to be calculated only once.
When doing the
ign it was controled that the basin was empti
ing rainfall.
rough i gn the necessary vo 1 ume of the basin for each
storm was determined to prevent the basin from flooding. A series
of basin volumes for each outflow level was obtained corresponding
to the 176 ra i nfa 11 s. These basin vo 1 umes were ranked in
cending order and the largest (corresponding to a return
period of six months) were plotted on a statistical probability
paper using the plotting formula
y.
1
=1,2 ... ,N (2.17)
yi plotting position for the basin volumes in increasing
(yi = lnF; where F is return period)
N = number of ted basin volumes (in this case 36)
The resul are shown in Appendix I.