Extracted text: 6.12 The ordinates of a 6-h unit hydrograph are given. Time (h) 6-h UH ordi- nate (m/s) 3 9 12 18 24 30 36 42 48 54 60 66 0 150 250 450 600 800 700 600 450 320 200 100 50 The McGraw Hill Companies Hydrographs 239 A storm had three successive 6-h intervals of rainfall magnitude of 3.0, 5.0 and 4.0 cm, respectively. Assuming a ø index of 0.20 cm/h and a base flow of 30 m/s, determine and plot the resulting hydrograph of flow.