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<br />Or Calculation <br /> <br />The second step in hazard classification is the computation of the flood flow <br /> <br /> <br />due to failure, but at a point downstream of the dam. Due to the effects of <br /> <br />side channel storage, infiltration, and channel roughness, the flood <br /> <br /> <br />hydrograph changes as it proceeds downstream. The following can occur: <br /> <br /> <br />1. The peak flow is reduced. <br /> <br />2. The base time is increased. <br /> <br />3. The hydrograph shape becomes more rounded. <br /> <br />We realized the volume of the flood would also be expected to decrease as the <br />___ ~ - __ --0_. _~__",-__ <br />-~ ~ ~--. <br /> <br />flood proceeds downstream. fuwever, any loss of volume is neglected for'tlie <br /> <br />( purpose of this analysis. <br /> <br /> <br />\ <br />" <br /> <br />This assumption is based upon flood channel <br /> <br />conditions that would be pre-wetted, so that loss by absorption of channel <br /> <br />. soils is negligible. <br /> <br />The relationships described above are illustrated in Figure '3, <br /> <br />cfs <br /> <br />cfs <br /> <br /> <br />Qr <br /> <br /> <br />,/ <br /> <br />HIS <br /> <br />.~ <br /> <br />Tp <br /> <br />.1 <br /> <br />I. <br /> <br />Tr <br /> <br />FAILURE HYDROGRAPH <br /> <br />ROOTED HYDROGRAPH <br /> <br />FIGURE 3 <br /> <br />Effect of Routin~ Upon Hydro~raph Shape <br />(Qp > Qr, Tp < Tr, Vp "' Vr) <br /> <br />s <br /> <br />:r <br />I <br />, <br /> <br />Hrs <br />