A major bridge is designed for a flow rate of 45 ft^3 /s and the bridge owner will take action if there is more than a 1% chance of the bridge flooding. The peak annual flow for the main river in the watershed is given below. Find Q100. Solution Given Data :- Designed flow rate = Recurrence Interval Period = n + 1 /m = 5 +1 / 3 = 2 Return period The 100- year flood 1/100 = 0.01 it means 1 % of chance of being in any on eyear. so we have to calcualte the possibility of an event occurs P ( x=1) = (100/1 ) x0.01 1 x 0.99 9 = 100 * 0.01*0.914 = 0.914 .

1. A major bridge is designed for a flow rate of 45 ft^3 /s and the bridge owner will take action if
there is more than a 1% chance of the bridge flooding. The peak annual flow for the main river in
the watershed is given below. Find Q100.
Year Flow (ft^3/s)
2001 20
2002 40
2003 60
2004 45
2005 35
Solution
Given Data :-
Designed flow rate =
Recurrence Interval Period = n + 1 /m = 5 +1 / 3 = 2
Return period The 100- year flood 1/100 = 0.01 it means 1 % of chance of being in any on eyear.
so we have to calcualte the possibility of an event occurs
P ( x=1) = (100/1 ) x0.01 1
x 0.99 9
= 100 * 0.01*0.914 = 0.914