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TABLE 3 <br />• PROBABLE MAXIMUM THUNDERSTORM CALCULATIONS <br />Thunderstorm CN 68 <br />Direct Runoff Increments <br />Time Incremental Cumulative Direct Runoff Incremental <br />Hours Design Rainfall Design Rainfall Cumulative Incremental Loss <br /> <br />0 0 0 0 0 0 <br />0.25 1.18 1.18 0.05 0.05 1.13 <br />0.50 1.59 2.77 .56 .51 1.08 <br />0.75 3.33 6.10 2.85 2.34 0.99 <br />1.00 0.83 6.93 3.50 0.65 0.18 <br />Compute Tp, Tb, qp for 1.00 in 0.25 hour triangular hydrograph <br />Tc = 1.19 hours, D = 0.25 hours <br />Tp = D/2 + 0.6 Tc <br />P = 0.25/2 + 0.6 (1.19) = 0.84 hour <br />Tb = 2.67 Tp = 2.24 hour <br />qp = 484 AQ = 484 (5.5) 1.0 <br />= 3169 sec <br />ft <br />Tp 0.84 . . <br />Hydrograph Plotting Table <br />• Incremental <br /> Hydrograph <br />Time ending Incremental qp for 1.0 in. qp for Begin Peak End <br />Hour Runoff Sec. ft. Incremental Time Time Time <br /> <br />0.25 0.05 3169 158 0 0.84 2.24 <br />0.50 0.51 3169 1616 0.25 1.09 2.49 <br />0.75 2.34 3169 7415 0.50 1.34 2.74 <br />1.00 0.65 3169 2060 0.75 1.59 2.99 <br />See Table 6 Hydrograph, Maximum Probable Flood, Thunderstorm <br />• <br />VI-19 <br />