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<br />t (hr) <br />Pi <br /> <br />\(mi) <br />= tf(hr) + C (mi/hr) <br /> <br />(36) <br /> <br />where: tf (hr) = time of failure for dam (minutes)/60 <br /> <br />To compute the peak depth at mile Xi' the user must fit K and m <br />coefficients for that X-section by substituting the specific depths and <br />topwidths at mile Xi into Eqs. (5)-(6a). The peak flow at mile Xi is then <br />compared with Qv (Eq. (7)) and Eq. (30) or (31) is used to find the peak <br />depth (hx ) at mile Xi' <br />i <br /> <br />I <br />I <br />I <br />, <br />I <br />I <br />f <br />I <br />i <br />~ <br />I <br />~ <br /> <br />The user may wish to determine the time at which flooding commences <br /> <br /> <br />and/or the time at which it ceases. To do this, the user must first specify <br /> <br /> <br />a flow rate, Qf that corresponds with flood depth at the X-section. <br /> <br />b <br />Qf = a hf <br /> <br />(37) <br /> <br />where hf = flood depth <br />and a and b are defined by Eqs. (9)-(10) using the K and m <br />coefficients fitted for the X-section at mile Xi' <br /> <br />This value for Qf is substituted into Eq. (38) to determine the time to <br />flooding, tfld, as follows: <br /> <br />tfld(hr) = <br /> <br />t (hr)- <br />Pi <br /> <br />(Q - Q ) <br />Pi f <br />tf(hr) <br />Qp Qo <br />i <br /> <br />(38) <br /> <br />where tPi is the time to peak calculated in Eq. (36) <br /> <br /> <br />tf is the time of failure for the dam, and <br /> <br /> <br />Qo is the nonbreach (spillway/turbine/overtopping) flow. <br /> <br />To determine the time flooding ceases, td' the value of Qf is substituted <br />into the following relation: <br /> <br />1-21 <br />