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U,BLE 2 PEAK flOWS FOR INTERMEDIATE REGIONAL AND STANDARD PROJECT FLOODS LocatIon Intermediate Reolonal Flood c.f.s. St"nd~rd proiectFlood c.f.s. Colorooo ~Iver above conflu- ence of GunnIson River GunnIson River at Red I aMdS Dam Colorado River below conflu- ence of GunnIson River 63,000 70,000 20,000 22,000 82,000 91,000 FREQUENCY Flow frequency curves On the streams unoer study were developed frOMrocordedstreamllowdata. The frequency of occurrence of the 1884 flood was appro~lmatoly " once In 250- to 300- year flood, whIch 15 considered to be ~bout the same as tor a Standard Project Flood. Floods larger than the Standard Project Flood wIll occur but ere beyond the scope of this report. HAZARDS OF LARGE FLOODS The a~unt and c~tent of damage caused by any flood depends On the topography of the area flooded,dep1"h and duration of flooulng, velocity of flow, rate of rise, and developments In the tlood olaln. An occurrence of an Intermediate Reqlonal or Standard Project Flood ontheColoradoorr,unnlsonRlversatthepresenttTt"ewouldre.,,,lt In Inund~tlon 01 re.,ldentl~1 ~rea.,; dama~e to roads, .,treP.ts, and publlcutllltlas; d3fi"'1et<:>"8rlcult<Jral landS and appurtenar.t 1"1- provements; and InterruptIon of traff Ic, Floodlol~t..r f lowl ng at hlnh velocIty anc carrylnn Iloatln'1 debris would create conditions haldrdous to persorls and property In flooded araas. in general, f IcodM wdter 3 or ~re feat deap and tlowino at a velocIty of 3 or more feet oer second could oasllv sweap a pcr~r oft hIs teat, thus creating" " i , \ detinltedangarol Injury or drowning. Sew"ge,qarbaqeandother organic materialS carried or deposited by tloodwater could create hazards to haalth. fLOODED AREAS A~O FLOOD DA~Ar,ES '0. dreasalong ". streams ;0 ". study area that \<Iould '" inun- dated 0, a Stanoard Project Flood are shown on Plato '. \<Ihich ;, also "0 Index to Plates 5-9. Areas that \<Iould b" flooded " ", Intermedl"te Regional and Standard Project Floods are shown In detail on Plates 5M9. As may be seen trOM these plates, flOOding along the Colorado and Gunnison Rivers would be confined to the Inmedlately adjacent OVer- bank areaS. Colorado River floodtlows wi II Inundate bottom landS along the north sIde of the river and low sandbar islandS I~edlately upstream frOlT'GrandJunctlon. The commercially developed Mea near the Fifth Street bridges and the residentIal area near Riverside Par~ would be throatened by the high flows of the ColoradO River. These tlows cen back Into the Connecticut Lakes area to the south of the river. The higher flows on the GunnIson River would flOOd agrIcultural areas UpM stream t~ tne mQuth. No Thorouohfare and R~d Canyons have no develop. anle Ilood plains until they reach the flood plain of me Colorado River. Areas subject to flooulns froM these creeks are also flootied by flows from the Colorado ~iver, F"loodd<ll"a8Elwouldconslstof depositIon of silt and floatable debrl s, bank erosion, a~d erosion of cllann..1 Islands. Aqrlcul tural crops would bodamaged by silt deposition ana drowning of crops. Flood/lows WOuld cause damano to buildings, eroda stre~ ban~s, end u~de~ine streets and lots. A$tandardProjoctFloodoouldcausernoreextonslvOdQ'l'l3j:lethdnan InterMediate ReqTonal Flood due to the wldor flood plain, greafer depth 01 flooding, higher velocity 01 flow and loncer duration 01 IIOOdln9. Plates 10~18 Sholol water surface profiles 01 the Intermediate Regional and StMdard >>roject Floods. Depth of Ilow In the Channel can be estirratod fromthesolllustratlons. TVDlcalcrosssectlonsof th<llloodDlaTnat sa I ect"d I ocat Ions, t""e'ther with tl1" water surf ace " I "v,~t I On'. and th!' "