# very very tough needs a genius

• Jan 12th 2007, 11:05 AM
question
very very tough needs a genius
a cofferdam has to be constructed in a river which has a stage-discharge relationship given by q = 12.74(z-18.63)^1.15 where q is the flow in m^3/sec and z is the water surface level in metres above datum. the cofferdam is expected to be in place for 2 years and the probability of it being overtopped by a flood must be less than 2%. calculate the necessary height of the top of the cofferdam above datum

here are some formulae and i have attached tables

gumbel reduced variate y = -ln[-ln(1 - 1/T)]

cunnane formula T = n + 0.2/m-0.4
• Jan 12th 2007, 11:18 AM
CaptainBlack
Quote:

Originally Posted by question
a cofferdam has to be constructed in a river which has a stage-discharge relationship given by q = 12.74(z-18.63)^1.15 where q is the flow in m^3/sec and z is the water surface level in metres above datum. the cofferdam is expected to be in place for 2 years and the probability of it being overtopped by a flood must be less than 2%. calculate the necessary height of the top of the cofferdam above datum

here are some formulae and i have attached tables

gumbel reduced variate y = -ln[-ln(1 - 1/T)]

cunnane formula T = n + 0.2/m-0.4

Still not enough information, or the explanation is so obscure so as to make
the problem incomprehensible to anyone not familiar with the specific domain
this question comes from.

RonL