A 75-acre development will consist of 35% pavement, 35% lawn, and 30% woods. Using the rational method, calculate the 100-year peak rate of runoff if the time of concentration is 30 minutes. The entire site runoff is drained to a detention basin. Using the IDF curves of Figure 3.1b in Chapter 3, estimate the required detention storage to create a 20% reduction in the 100-year peak rate of runoff below that of the existing conditions.

The site is entirely wooded under the predeveloped conditions and has a time of concentration of 60 minutes.