Engineering and Contracting . Most of the run-off formula arc based onconditions existing in the particular city orlocality for which they were derived and itis, therefore, evident that these should not he time permits of a varying rate of rainfallinmiediately dependent upon the area, shapeand slo])e of the territory to be \lso, on account of the unusual topographic of time should he accurately determined. In view of these facts, it was concluded toadopt the rational method in determiningthe amount of storiu drainage for wdiich pro- TABLE or INTENSITIES. FOR l-M- a Storm of May ^O
Engineering and Contracting . Most of the run-off formula arc based onconditions existing in the particular city orlocality for which they were derived and itis, therefore, evident that these should not he time permits of a varying rate of rainfallinmiediately dependent upon the area, shapeand slo])e of the territory to be \lso, on account of the unusual topographic of time should he accurately determined. In view of these facts, it was concluded toadopt the rational method in determiningthe amount of storiu drainage for wdiich pro- TABLE or INTENSITIES. FOR l-M- a Storm of May ^O. 1902 Q . - July 17. 1912 i . . ZZ. 1906 , . ,. 5 . 1837 o . Aug. 3. 1900 • . ,. May 27. 1899 — Adopted Curve for Cioti O (I ^) T,me inm,nu+es Int^nsit^ Time inminutes Intensity b 7 17 80 1 79 10 507 85 1 74 15 4 14 90 169 20 3 58 95 1 64 25 320 100 160, 30 2 92 105 1 56 35 271 no 1 52 40 2 53 115 149 45 2 39 120 146 50 2 26 l?5 1 43 55 2 16 130 1 40 60 2 07 135 1 38 65 1 99 140 1 35 70 1 91 1+5 1 33 75 1 95 150 1 31. ^60 65 TO 75 So 55 90 5^ DURATION OF DOWISPOUR IN MINUTES Fig. 1. Diacrrm Showing the Relation C^twcen :ty ard Curation of Rainfall at Cincinnati from 1871 to 1912. used excepting under similar , some formulre are made dependent uponan adopted maximum rate of rainfall whicliis kept constant. On the other hand, the useof the so-called rational method of analysisthrough the introduction of the element of features prevailing in Cincinnati, producingnumerous small drainage areas with com-paratively steep surface slopes in the outlyingdistricts and IJat slopes in the older portionsof the city, it is important that the properrainfall intensity and run-off for short period? TABLE U.—ULN-DFF FROM IMPP (VED AREAS IN TYPICAL COMMERCIAL DISTRICT.— ; (WALNUT STREET).Area— acres. * Area co\ered ort1< Character of District—Commerc^lnc»» houses. No undeveloped and gravel. Character of Improvement. Roofs Public and com
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