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<br />V-2 <br /> <br />e" Freeboard of from one to two feet, except where overbank <br />flow does not effect or cause damage. <br /> <br />f. Hydraulics roughness In accordance with the Denver Regional <br />Council of Government~ and other suitable criteria. <br /> <br />g" Grass cover of crested wheat grass, or equal. <br /> <br />h. Use trickle channels for low flo~ls with capslcltles of about <br />one per cent of design flow, but not to exce,ed 250 cfs. Use <br />rlprap, concrete, or other pr'otec:tlon to pre've:nt erosion. <br />Maximum flood depth over trickle channel" 8 feet; maximum <br />velocity" 8 fps. <br /> <br />I. The bottom of channel shall have a !,lope tO~lard the trickle <br />channe 1 . <br /> <br />j. Froude number (turbulence factor) shall be less than 0.80. <br /> <br />k., DesIgn top width to range betw,.en 20 to 40 tImes the cles19n <br />depth. <br /> <br />2. Natural Channels. Natural water-rays I~lll be use,d wherever fe,3slb!e. <br /> <br />a. Channel and overbank capac I ty rnus t be adequel te, for des I gn <br />runoff . <br /> <br />b. DesIgn velocIties, as computeld, should not generally ex- <br />ceed critical velocity as Indl<:at.ed by bac~'ater curv,a cornpu- <br />tatlons. ExceptIons permltte1d In short reaches where variances <br />are envIronmentally reasonable. <br /> <br />c. The flood plaIn lImIts must be dE.fined based on future Lows. <br /> <br />d. FIllIng offload plaIn fringes should be llmitEld In order to <br />maIntain channel storage capElblll ty. <br /> <br />e. Hydraul Tc roughness should be: representative, of reason,ably <br />maIntained channel conditions. <br /> <br />f. Perform backwater curve compLitatlons based on existing condI- <br />tions with assumptIon that flood plaTn lImits will be revIsed <br />as brIdges are replaced or new road~lays are constructed. <br />