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3 3 I!. IiYOROLOGlC A~ALYSIS The hydrologic analysis conducted focused on determining the pea~ flow and volume of flood producing rainfall events;n the Town of Haxtun. To hei. litate thl!,nOdelingof a f100d event which adequately reflects, as closely as possible the actual situation, the hasins draining the Town and surrounding aredS were divided into two categodes. These were: (1) the major basins whiCh lie north, east and west of the Town, and (2) thP. basins lyiogwithin the Town limits. This was done because of the nee<'! to apply hydrologic I~ethods which are best suitect to agricultural areas Mained by "natural" draina!leways, and an urban area which is drained by a street and storm sewer system. Thefoll<:Ming is a discussion of thebasin(s) and our resu1ts. nortllWt'stern parts of Plll1l ips County. These soils take in water rapidly to very rapidly and Ilave rapid internal drainage. Available water holding capa- city 1s high ill tile subsoil. Because the surface layer has rapid per- meability, there is little runoff. Natural fertility is mO<lerate to high, but these soils are subject to son bl('Ming unless they are protected by growing crops or crop residue. These soils are classified as a "B" soil type, as defined in the SCS hydrologic methodology, and yield a 71 CN-value. Soils Son s witlli n the study area are generally clas~ified a~ sands and loamy sands, known as the Haxtun Series (Reference 1). The llaxtlJn series consists of deep, wel1-Mai nerl loamy sancts and sandy loams of the llpl ands. Thes~ snlls .)rE.'nearly level tnmoderately sloping and.'lremostly in the Mrth-central and Major Drainage Basin Description Sllown onF1gure 1 olre the major drainage basins whiCh are tributary to the Town ofllaxtun. Tho flows frOlll these basins have been calculated at the Town limit, and input into the hydrologic model applied in the Town. The basins have been numbered 1 through 3. The fhe principal offsite drainage lJasins drain into the north and '/lest sides of the Town. Three of the basins eventually have acommonconfluen,e point in the downtown area on Fletcher Street near Washington IIvenue and Colorado Avenue w~ere they gather to flow Nst down Fletcher Street (Canal Street). Ba sin 1 contai ns 263 a,res and dra ins into the northe~st corner of the Town then so,jth along the east edge of Town to Fletcher Street. Basin2 has 1,S70acres and flows into the northwest corner of theTO'lIn, then 'on- tin'.I"~ Sf\utheasterly zl'Jlag'Jin'J thrOUr!n the ~tre..t.~ to th" ~onf1IH'n~e point on F1 etcher Street between Co 1 orado Ave nue and Wa ~hi ngton Avenue. Bas i n 3 ,on- tains 180 acres and drains into the southwest corner of the Tmm at Joe Avenue and north of the railroad. The flows then proceed east along the north edge of the railroad and a10ng FletCher Street to the same COnfluence point as llasin2. Basin 4. with about 145 acres, flows int') the southwest ,orner of the Town at Highway 6 lJetween Joe Avenue and Falrview Avenue. The flow then proceeds east. southoftheral1road. toa railroad pipe crossing atColorarto Avenue where the flow goes north to the,onfluence point of Basins 2 and 3. Basin 5 does not flow into town but its 190 acres does drain into the drainage ditch between FletCher Street and the sewage la~oons east of Town. These five hasins have slopes that range frOll1 0.3 percent to 0.5 percent. All of the area offsite f!'Om and in,luding the Town are trilJutary to the North Fori:. of FrencnnanCreek. General Basin Characteristics Climate This area of P~i11i ps County has a temperate, SE!fI1i arid Cl imate that is typical for the High Plains. Days are hot during July anr1Aug1jst, but except for July. nights are cool in summer. In winter, whiCh is cold, the wind is considerable an<lblows the snow.l>utwarmchinook winds occlJroccasiooal1y. The growing season is about 147 days, anct the mean annual terlperature is about 49"F. The amount of preci pitati on va ri es from year to year, and cC<'les '~os tly as rain d'..i"i~~ April, "iay, .J,-,ne, Mtl .1'11y. Th.. ~n",,~l ~v..rag" pr"cipit~tion is 17.8 inches. Wind has influenced so11 formation by removing soil material frorn on" p1ace and depositing it in anotbor. The effect of the wind can be socn in the pattern of ~011 areas shown on the soil map in the Philli ps County So11 Survey. Long, narrow soil areas that trend southeast are distinct and Wt're forrned by winds blowing from the northwest. The pattern of surface drainage thatwascutbyrunoffwateralsofollowsasouthcasterlydirection.