Extracted text: catchment areas are given in Table 2-1. (a) Using the given IDF curves and the Rational method, calculate the 50-years design peak flow (in cfs) at the catchment outlet. (b) A levee is to be designed to protect the area near to the catchment outlet using the estimated peak- flow. If the design life of the levee is 20 years, calculate the probability (%) of failure of the levee during its design life period. Area 1 A1 A2 Area 2 C1 Table 2-1: Sub-catchment properties ti Catchment property Area 1 Area 2| Area 3 Catchment area ( km²) 10 20 Area 3 A3 Runoff coefficient 0.2 0.9 0.4 C3 Time of concentration (minutes) 20 10 20 t3 Catchment outlet Figure 2-1: Watershed IDF curves for storms in vicinity of example site 9 50 8 25 8 7 1아 5 4 3 2 1- 1 05 10 15 20 30 40 50 60 70 80 90 100 110 120 130 Time (min) Intensity of rainfall (in./hr)