The document provides instructions to use the Alternating Block Method and Steel and McGhee formulation to determine the design storm hyetograph for a 6-hour storm with a 10-year return period located in Carbondale. Given values like the storm duration, return period, and location-specific coefficients, the solution calculates an rainfall intensity of 7.17 inches per hour over 15-minute increments.

1. Using the Alternating Block Method, determine in 15 minutes' increments, the design storm
hyetograph for a 6-hr storm in Carbondale with a 10-year return period. Use the Steel and
McGhee formulation.
Solution
given storm duration = 6 hr
return period = 10 yrs
for carbondale : C = 96.6 , e = 0.97 , f = 13.06 , Td = 15 min = 0.4 hrs ( these values vary from
place to place )
i = C / ( Ted + f)
on substituting ,
i = 96.6 / ( 0.4 0.97 + 13.06 )
i = 7.17 in / hr