Question

un has been built to protect homes in a floodplain until a major channel project can be A cofferdam has been built to protect home completed. The cofferdam was built for the 20-yT years to complete. (a) What is the probability that the co years? S the probability that the cofferdam will not be overtopped during the entire three Pexo = 1-1/20 =0.95 (b) / What is the risk to the cofferdam? R=1-(1-0.05) R=0.142625 = 14.26% ) What is the probability that the cofferdam will be overtopped only in the third year? /20 = 0.05 = Pex) A probability plot of 66 years of peak discharges for the Kentucky River is shown below. Return period (y) 1.01 1.11 2 10 20 50 100200 Peroen greater than 99.9 99 98 05 90 SO 70 60 50 40 30 20 10 5 2 1 05020.1 Assumed historical events MIT (5330001) 90 95 98 99 0.10.2 0.5 1 2 3 10 20 30 40 50 60 70 80 Percent less than (d) What probability distribution is being used? X log Normal (e) What are the mean of the peak discharges? 10,000 (1) What is the probability that the annual peak flow will be greater than or equal to 50,000 A/s in any given year? I 1-0.20 = 0.8= 80%

Answer 1

during (a) Probablity that coffeodam will not be overtopped the entire three years. P(x) = o ccusence of ovenduming = bo 80, not overtuming - 1- to 0.95 (b) Risk to the coffendam REI-(1-1) = 0.142625 - 14.26% (c) Probablity that cofferdam will be overtopped only in 3rd year PCX = ovestoped - to P(x) = not overtoped - 19 PCX)= 19 xl xbo =0.045) Id) Gausian or Namal distribution is used. e) Mean off peak discharge - KQ. 110.000 (fl Annual peak flow will be greater than to equal to 50,000 feel in any given years to '1-0.20 = 0 g = 80%