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Ill. RESEARCH AND HISTORY OF FLOOCING the City bec.1II;c .1 ".1st lake" (Reference 6), and thilt runoff flowed do~'n several streets at one to foor foot depths. Road and bridue da'.1.1ge WJS sustalned.asl'iell a, considerable danaue to privote hOllles and I'roo perty. The base data utilired for tile study included local rainfall records, the Soil Conservation Service (SCS) Soil Survey, as well ver- b~l and newspaper accounts of si unificant storr,1 events. Rai nfall rccordsI1avebeenmaint.1irredfor54yearsbytheUnCOlllpahureValley Water Users Associ.1tion (UVWUA) at North 6th Street and Park Avenue. Records dt the Montrose r,i rport Iidv~ been IIlaintdirreu for 27 years by the Nation.1l Weather Service (NWS). These two records provided excel lent 10C.1l rai nfill 1 base d~ta. Table 111-1 presents d tabul ation of the major storms of record. The National Oceanic and Atmospheric Administration Precipit ation- Frequency Atlas (Rderence 1) proviued regional rainfall inforl,ation for tile State of Colorado. and provided data for the upper ba,in a rea5. Theses "Soil Survey of theOe1ta Montrose Mea." (Reference 2) provides a detailed soil s report for most of tlie st~dy area. Al so con- sideredweretliesoilsdatilmadedvailablethrou,;hthellpril,1976 "Geologic Hazards, S~bsurface Soil-Groundwater lnvest i gat iOrl arid General FoundationOesignCriteria" report prepared for the Mont rose Co~nty Co".niss ioners by Geotechnic~l Engi neers, Inc. (Reference 27.). Hydrology dnd flooding reports addressing several nearby and/or hydrologically sinlilarbasins havebuefl studied as pdrt of this andlysi s. The st~dies reviewed included tlm Ridgeway Dam hydrology and several srllaller basin studies for wl1i~h 5trealn flow records were available. InFebrUdr)',1963,Chinoo.. winds c.1lised snoWf"elt which res,l1ced in f1 ood i flg when ~he Md inS t reet Lro SS i n U of I~orlt ro se A no)' 0 bee cl IIIe bl{)c,ed witll debris. Thio flo(,d event, however. was not lhe di r~ct res~lt of precipitation. A thunderstorm on June 27,1%1, durrlped over an inch of rain ana hail on the city causin9 floodinu on [;O)ny stnets, notably Uneoll1~ilhgre fl,venue imd ~1di n Street. Trl~ Loulsenll izer Canal [Jredched Cdusing floodi ny of a fi e 1 d and SOllil' crop dcllli~~e. The lOore recent de9n:c of urb.1njz~tior\ and !jrowth within the city and its environs IIIdkes the ,;re,cnt day potential hazardc'lenl;lOrc significant thiln these reports in~icate_ Figure 111-1 presents summ.ries of available newspaper articles relating to past floodin~. The above data was forther supplemented by local fieldrecon- rldissanee by flydro-Tri ad, Ltll. stdff. Ddtd gather~d included jihoto- graphs of basin con(jitions. strea'nandCandl flow characteristics , survey of the str~",;, cros,'inys, ~nd infor-,,:ation on the urban dra i na!j€ situation. Since no strearr. flow n::cords were aHilable in the stuuy bas in, field observat ions W8rc IlJade Jnd verb~l Jccounts of flooding recorded to aid ln corroborating hydrologic analysis results. The OHlce of the State Engineer. Oi vision 4; U.S. Borea~ of Reclamation (Grand Jundion office); UVIIUA; Montrose CDrrwnuni ty Devel o~ment Dept.; S.C.5. (Montro,;e fieln offi~e); Montros!' County Pl anning Depdrhlent; Colorado Water Conservati on lloard; ~nd vari ous City and County stdff were solicite<l fo,-infor..lationconcern ing fl ""rlin~. (;ef\"r~l COrm1"nt~ were nht"in~d nn th" flnnding inlOJact on the City and its environs,specificallYds it affectectthe respective are,lS of inter('st or responsibility. There are few for'~a 1 ly doculllented records of past fl oodi ny in ~ontrose. f,n event in tile late SUmller of 1933 is indiCilt ive of the ;Jo:ent i al danger, however. l-1ea'l)" rain on tl.O CO~Sl:cut i ve days In Sl:~te'lber, 1938 CdU5e-d flcoding frOJII Ory C~dar Crel'~, as well oS v,ontrose Arr'oyo. A.vailable infunrlalion hdiCcltes tllat "a por'tirm of -15- -16-