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<br />FLOOD PLAINS MANAGEMENT <br /> <br />STUDY <br /> <br />TOWN OF LIMON, COLORADO <br /> <br />APPENDIX <br /> <br />THEORETICALPLOODWAYOOMPUTATIONS <br /> <br />PREPAREDBYTHF. <br /> <br />V.S DEPARTMENT OFAGRICULTlJRE <br /> <br />SOIL CONSERVATION SERVICE <br /> <br />DE~"ER, COLORADO <br /> <br />IN COOPERATION WITH TlIE <br /> <br />COLORADO WATER CONSERVATlON BOARD <br /> <br />TOWN OF LIMON <br /> <br />HIGH PLAI~S SOIL CONSERVATION DISTRICT <br /> <br />MAR011983 <br /> <br />lDZ\) <br /> <br />W(i),(iJS~)(~~~, D\ <br />WX "" 01 \Jtl \U\ <br />.lli .__~ -' <br />LJ~O-'ciR",iJ0\N';1E~ <br />C '"'._ -,,,, , ",n~~l) <br />e"c,,,,..,,-,'----" <br />co:!".:.-.-.' - -~ . <br />of Ag~ic~ltu~e, Soil <br /> <br />THEORETICAL fLOODWAY APPENDIX <br /> <br />This appendix was prepa~ed by the U,S. Depa~tment <br /> <br />Conservation Se~vice, in cooperation with the Colorado Water Conse~vation <br /> <br />Board, and the Town of Limon, Colorado. <br /> <br />Included are tables and ~ps that ~efIect a theoretical enc~oach~ent on <br /> <br />the natu~al 100 year frequency flood plain sufficient to cause an increase <br /> <br />in water surface elevation of 1.0 feet. <br /> <br />This Infor~ation ahould be used in conjunction with the main reporr <br /> <br />completed and dl&t~ibuted in September 1982. <br /> <br />The procedure used to develop the enclosed data was encroachment Optlon <br /> <br />4 of the U.S. Army Engineers HEC2 Compute~ P~ogram. The. p~ogrllm sets <br /> <br />encroachrnent lilllits at each cross section by e1eminllt1ng theincre ased <br /> <br />conveyance from the extremit1es of overbllnk areas. The progrllm remov~1I an <br /> <br />equal percent of conveyance from each s1de of a cross section 1f possible, <br /> <br />If the~e is insuff1cienc conveyance in one ove~bank area, the other one <br /> <br />eOmP'H1satell. The p~ogra", will not encroach into the channel as defined 1n <br /> <br />th~ ~"t~, ...1110 br1dg"~ "".~.. "ot ..ncro"cherl upo", Th~ romnnted incr~,,"e in <br /> <br />water surface elevation may not always be exactly eqUAL to the desired vlllue <br /> <br />(1.0 ft.). This is because of (1) redistribution of flo~ and velocity when <br /> <br />c~oss sectiens are mod1fied, and (2) backwater effects from downst~eam <br /> <br />encroacl-..ent"'. <br /> <br />The dat~ 15 prp~"nt..1 in tllhl"lI thllt IIho~ flonrlw"y width, IItlltiontng, <br /> <br />velocity, water surface elevat10n /lnd 1ncremental rise at each cross <br /> <br />section, Tho. map. reflect a 1lIOdifio.d flood bounda~y neceasary to achieve <br />