10.18. You are designing a drainage system for a residential site in Atlanta using a 10-yr return period. The site has an area of 1 ha, a characteristic flow length of 100 m, an average slope of 1%, a characteristic Manning's n of 0.25, and Type B soil. Drainage regulations require that the kinematic-wave equation be used to calculate the time of concentration, and you are allowed to use either therational method or the TR-55 method to calculate the peak runoff rate. it is suggested that you usethe rational method with a runotf coefficient of 0.4, which is typical of residential sites. What curvenumber would be required for both the rational method and the TR-55 method to give the same peakrunoff rate?Droduce.

Fig: 1

Fig: 2