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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 f1o~ls with caps,cltles of about <br />one per cent of design flow, bllt not to exce,ed 250 cfs. Use <br />rlprap, concrete, or other pr'otectlon 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 I . <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.'ays 1~111 be use,d wherever fe,3slb!e. <br /> <br />a. Channel and overbank capac I ty mus t be adeque, te, for des I gn <br />runoff . <br /> <br />b. DesIgn velocIties, as computeid, should not generally ex- <br />ceed critical velocity as Indl<:at.ed by back\-rater curv,e cornpu- <br />tatlons. Exceptions permlttEid 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 offlood plaIn fringes should be llmit..d In order to <br />maIntain channel storage cape,blll ty. <br /> <br />e. HydraulIc 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 plaIn lImits will be revIsed <br />as brIdges are replaced or new road~lays are constructed. <br />