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IS 16 m~jor basin hydro graphs. The 1 nitial peak is the resul t of the thunderstorm occurring over the Town itself. The re1dtively quic~ time to pNk is the result of the high-intensity thunderstorm used in the hydrologic model, in combination with the high rates of runoff, characteristic of urban areas. The Sllcondarypeak is the result f10w moving through the Town, whichori ginatedin theagric'lltural areas north and west of tl1eTown. The cultivated nature of the area, in cOO1bination with the salls ab11lty to infiltrdte a high percen- tageoftheinitial rainfall, result in the time to peak being lagged substan- tially behind the passing of the urban flo.ls, and a rTMJch lower unit discharge (e.g., cublc feet per second per unit areal. From the analysis of the flood hydrographs, a storm sewer system to drain the Town sh001 d be sized to adequately con~ey this type of double-peaked hydrograph. A proposed storm system, from Fletcher Street and Washington A~enue to the outfall of the open channel located at Fletcher Street and Cooper Avenue, shoul d be sized to con~ey peak flows from the initial, or in-Town storm e~ent. Conversely, a storm system proposed to direct fl ows from northwest portions of Town to Fletcher Street (i.e., that portion of Town receivingm.ajorbasin flows from offsitel,must be slzed toadequatel yconvey flo.<s resulting from the longer duration storms, originating outside of tM Town. 111. HYORAULlC,I,NALYSIS Hydraulic analysis for the Town of Haxtun have been conducted for the 10. and 100.year frequencies. This work consisted of analyzing the local stonn and street flow systems within the Town, and an analysis of the open channel draining themajor1ty of the Town, to the east. A discussion of existing systems follows. The Town 1tse1f is drained largely by a system of streets and cross p ans, which tend to concentrate the flow in Fletcher Street. The rnajorlty of the streets within the study area have curb and gutter, and only a few storm sewers are functional. Unpaved streets adjacent to the ral1road right-of.way cause sediment deposition along Fletcher Street and at se~era1 other 1ntersec- tions1nthedowntownarea. \llthinthenorthwestport10nofTown, the natural drainageway has been blOcked by urbanlzat10n, and flows originat1ng on the agrlcu1tuNl areas northwest of Haxtun move overland and eventually into the street system. Two natural channels drain the Town. The first channel begins at Joe Avenue, and runs along the north sldeof the Chicago, Burlington and Qulncy Ral1roadtracks, tennlnating at approximately Utah Avenue. This channel has no outlet structureO/hich forces ponding and debriS buildup. Thesecondchan- nel runs north to ,outh along the rear lot lines on the cast side of Walker lI~enue. Th i sChanne 1 I s hea~i 1y overgrown, and term; nates at Fl etcher Street. The majority of the Town is drained by a Qrassl;ned natural channel which starts at the east tennlnus of the Fletcher Street box culvert, and flows throughpasture1and,andinbetweentheTown'ssewagetreatmentlagoons. The grade of this channel is extremely mild, and forces flows to pond and stagnate at se~eral locations along the channel. This channel is drai ned I>y three c~lverts under County Road 7. The existing storm sewer facilities are detailed an Figure 5. Floodplain Description Figure 5 presents the lOO-year floodplains with the Study IIrea, utilizing the flow rates generated in the hydrologic analysis. The floodplains were ~el lneated using field measured sur~ey data of street cross sections, channel crosssectionS,loca1 informaticn supplied by the Town and its residents, and throughcomputerizedanalys;s.