42 



SEWER DESIGN 



one exception, been exceeded in any marked degree. It is 

 further probable that in each of these cities storms giving rates of 

 rainfall for any length of storm up to forty minutes will reach the 



values given by the curve y 



105 



at least as frequently as 



two or three times in ten years." 



In St. Louis Prof. Nipher has used the same method to 



STORM INTENSITIES 



AT 



ROCHESTER, N. Y. 



234 

 DURATION OF STORM IN HOURS. 



FIG. 6. 



determine the probable intensity for a given duration, and has 

 plotted the storms of that city in the manner indicated above. 

 He also assumed an equilateral hyperbola as the enveloping 

 curve, and determined its equation to be 30; = 360. This was 

 made up from the rainfall records of St.- Louis extending over 

 a period of forty-seven years. 



Kuichling plotted (see Fig. 6) the local data of Rochester 

 combined with that of two neighboring stations, and used two 

 straight lines as the envelope of the points instead of the hyper- 



