Flood Insurance Study, City of South Jordan, Utah, Salt Lake County

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1994

Flood Insurance Study, City of South Jordan, Utah, Salt Lake County

Federal Emergency Management Agency

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Recommended Citation Federal Emergency Management Agency, "Flood Insurance Study, City of South Jordan, Utah, Salt Lake County" (1994). All U.S. Government Documents (Utah Regional Depository). Paper 201. https://digitalcommons.usu.edu/govdocs/201

This Report is brought to you for free and open access by the U.S. Government Documents (Utah Regional Depository) at DigitalCommons@USU. It has been accepted for inclusion in All U.S. Government Documents (Utah Regional Depository) by an authorized administrator of DigitalCommons@USU. For more information, please contact [email protected]. FLOOD INSURANC STUDY IIOTIC! 10 VLOOD IBSUlABCB STUDY USBRS

Co~iti •• partlclpatinl in the If.tiona1 Plood In.urane. Proar .. have e.t.blbbed repo.itorie. of flood hazard data for floodplain JUnaaeMDt and flood in.urane. purpo.... !hh Plood In.urane. Study _y not contain aU data available within the repolitory. It i ••elvil.bt. to contact the co.tuDity repolitory for &oy additional data.

Part or .U of thi. PLood In.uranel Study ..,. be reviled and republi.hed at aoy ti.. ,In addition, part of tbi. Flood la.urane. Study ..y be reviled by tbe Letter of Map aevilioD proc••• , ¥bieb doe. not involve republication or rediltribution of tbe PLood In.urane. Study. It ia, tberefore, tbe re.ponlibility of tbe uaer to conault with cO.r\UDity officiala aad to cbeck tbe c.~ity repoaitory to obtain the moat current 'lood Inauranc. Study caponenu.

Tbi. publication incorporate a reviaiona to tbe ori,inal 'lood In.tlraDce CITY OF Study. Tb.ae reviaiona are pre.ented in Section 9.0.

SOUTH JORDAN, Thic preUainary reviaed 'lood In.uraace Study containa only profilea added or revhed aa part of tbe renudy. All profilea will be included UTAH in the final publiabed report. ,SALT LAKE COUNTY

REVISED: SEPTEMBER 30.1994

Federal Emergency Management Agency COMMUNITY NUMBER · 490107 Ii",·/- r. ' ~ //1. / TABLE or CO!!'U!!TI TABLE 9. cotrmITS (Cont'd)

Pale 1.0 ImoDVCIIOM Page

1.1 Purpo •• of Stud,. t.2 Authority and AckDovled... nu 1 . 3 Coordination •••••••• Pilure - Vicinity Map 3 Pigure - 'loadw., Scheaatic 14 2.0 AlIA SDIDIED

2.1 Scope of Btudy 2 2.2 COCDUDity De.cription 4 2.3 Principal 'load Probl._ Table 1 - SWIID4ry of Discharg•• 9 6 2.4 Plood Protection "ea,urea T.ble 2 - Ploodway Oeta 12 6 Table 3 - Jordan liver Proposed De,iln Di.charlel 18

3.0 QCIRRIMC I!Bl!!OPS

3.1 Hydrololic Analy ••• 7 3.2 Hydraulic Analy ••• Ezhibit 1 - Plood Profile. 8 Dry Creek Panels OIP-OJP Willow Creek Panels 04P-05P 4.0 PLQop P!.\I' IWMCIIIIRT APPLICATIO!S 10 Jordan River Panels 06P-07P 4.1 Flood IoUDclari •• 10 4.2 Pl"oct_,.. 11 PUBLISHED IBPAIATILY' s. C IlSl/I6IICl AlPLICAIIO! 14 Flood Insurance late Map Indes Flood Insurance late Map 5.1 .each Det.rwin.tion. 14 S.2 Flood a.&ard 'actor. (PHP,) is 5.3 .10od In.uunce Zone. 1S 5.4 Plood Io.urance ht. Map De.cription 16

6.0 rnA ID1DUS ••••••••••• • •••••••••••• 16

7.0 LQCAUO! DATA or ...... 17

8 . 0 8I1LIOCIAPIX A!!!l urlll!!C!I .•.••...••. • .• • .. 17

9. 0 1E'fI1I0! DIIClInIOIS 26 9.1 'int levhion 26

i i . I An inter-.diat. ~uni ty coordination ...ting was held on February 18, 1982, to allow ~nity repre.entaUve. to review the draft .tudy. Repre.entative. of the Pederal Bllergency Manage.. nt Agency, 1.0 IR'fIOJOC'rI(II the .tudy contractor, the U.S. ArllY Corps of Engineer., Salt Lake County, and the CiU•• of Sandy City, Riv.rton, Bluffdale, Draper • ....t Jordan, and South Jordan attended the Meting. Representatives 1 . 1 Purpo.. of Study trOW! sever al of the ~niUe. west of the Jordan River expressed concern that only approxiJlate atudies had been perforJlied on the '!bt. Flood Inlurance Study inv•• tigat e. the exiatence and aeverity .phe_ral atre_ that drain the Oquirrh Mountain.. It was explained of flCXJd haaard. in th. City of South Jordan, Salt r..k. County, that this .a. done because of the li_ited developaent on that side tJtab, and ala in tba IldainiaUation of the National Flood Insurance of the valley. Act of 196. and the Flood Di... ter Protection Act of 1913. '1'hh Itudy wl11 be UHd to oon.. rt South Jor dan to the regular prograa A final ~unity coordination Meting for Salt Lake County and of flood inaurance by the Pederal _'ganey Managuent Agency. the CiUe. of Riverton and South Jordan .as held on Deceaber It, LocaIl and regional planner. wl1l u .. thi. study in their efforte 1983. In attendance were repre.entativ.s of the Pederal Ellergency to pr~ eound flood plain __g_nt . Manag_nt Agency, the study contractor, the county, al'd the incorporated ~nit1es. 'J'Wo ..jar concerns raised at the Meting In eo.e atate. OE ~nltl •• , flood plain .ana~nt crlteria vere that the studies did not reflect flows frc. the 1983 flood, or regulaU0n8 _y I.lat that are ~1'. r ••trictive or ecaprehenllve and the conversion of the detailed study r.aches of the Jordan than tboM em which tile.. federally lupported .tueU•• are baaed. Riv.r between 2100 South Street and the North Jordan Canal Diversion '!be.. criteria ute preee4ence ewer the .lnt.. Pederal criterla Daa to approx1aate study. It .a. agr.ed that these probl•• would for purpoal of legulatlng ctt".los-nt 1n the flood plAlln, •• be addreuec1 during the appeal. period along with other aincr Nt forth in the c::ode of ,..,81 Ragulationtl at U CPR, 60.3. concerns raiNd by the individual co.aunities and the rounty. All In IIucb ca... , howe.. " it -.11 be underltc:lo4 that the State requesta were considered and, where appropriate, were acted upon (01' other juriadlctional agency) ahall be able to explaln the.. in the preparation of this study. requlr~ta and criteria. 2. 0 _ STIlDIBD

'l'he 8OU1'ce of authority for thi. Plood Inaurance Study i. the 2.1 Scope of Study Rational Flood Inaurance Act of 1968, a. _nded. 'l'tlia Plood Insurance Study cov.rs the incorporated areas of the 'lb. bydrologic and hydraulic analYH. for thia .tudy ver. perfor-.d City of SOuth Jordan, Salt Lake County, Utah . The area of study by RDUina, Brown and Gunnell, Inc., for th. Pederal _rg.nc:y ie ehown on the Vicinity Map (Figure I). lIaM~t Agency, under Contract Ro. &-"593. 'lbi. work, which wa. COIIIPlete4 in lII.y 1982, C09.red aU .ignificant flooding aources 'l'tle Jordan Riv.r and Dry and ..illow Creeks were studied in detan affecting South Jordan. for their entire length within the ~unity.

1.3 CoordinaUon '1'he cJetalled study reach of the Jordan Riv.r within South Jordan wa. converted to approxillllte study. 'l'tlia change r.sulted froa 8tre_ de.ignated for detailed and approxiaat. study were identified unc.rtainti.a in frequency analysis of the hydrologic data and at a ..Ung in Sept__ r 1977 attended by repre.entative. of frOli uncertaintiea in hydraulic .adeling caused by COIIpleted and the Itucty oontractor, the Pederal ...rgency llana~nt Agency, ongoing .o4it1cationa to the river channel initiated atter the kIt r..te County, and the City of South Jordan. ...ulte of the oc.pletion date ot thi ••tudy. In addition, downstre.. of the hydrologic and hydrauUc analyae. wre coordinated with repr ••enta WOrth Jordan Canal Diveraion 0.., proble. were encountered with U ... of the S.lt r..te County Public WOrk. Depart:.ent, Plood Control elevation data on the orthophoto topographic ..pe used for the and "tel' Quality Di.i.ion, the 0.8. ArIlY C»rpe of lIngi,,"r., detailed flood boundary delineationa, th.re were alllo di.crepanci.s anLt the 1ncorpcxated ~nit1e. of kIt Lake County. between the re.ult. of the step-backwater analyaie and the detailed flood boundary delineation.. Down.tre.. of the diveraion du, approxillate flood boundar ies vere taken fro. the Flood Basard Boundary Map (.. ferenee 1) . Up.tre.. of the diversion duI, approxi ..te flood boundaries were adopted fro. the atudy contractor'. detailed 100-year flood boundary delineations. , .- .. ' , --

.- I ,.' oJ' .. -- .. ...' ,-, - - -- -

fl"111 thOle area•• tudied by detailed methods were chosen with considera tion ,iven to all propoaed construction and forec.,ted development flow .lIOothly. This point coincide. with a gradual deterioration tbrou&h 1987. of river quality a. it proce.d. downstream. Mid .. and Bingham. Creek. were studied by approximate methods . The County ...terplan use. the canals to carry .torm runoff to the Preliminat'y hydrologic and hydraulic analyses for these !Creams natural cb.nnels. The eace .. from the canal would be discharged to revealed tbat tbe approzimate 100-year flood boundaries shown on the natural channel. Hany improvements to the canals and the tbe Plood aazard Boundary Hap (aeference 1) were accunte; cbannele are required before this system can fully function. tberefore , the Flood Hazard Boundary Hap was cho.en .s the source of .pprozimate flood boundari .. for these stream•• Dry and Willow Creek. are intermittent stream. that drain the .outhea.tern part of the valley. These stream. have fairly steep Approai ..te .naly.e. were u.ed to .tudy tho.e are., having a low gradient. a. they era .. the terraces, but become quite flat as they develo~nt potential or minimal flood hazards. The scope and reach the valley floor. _tbods of study were propo.ed to and a,reed upon by the Federal !Mr,ency KaDa,_nt Agency and tbe City of South Jordan. Two intermittent .tre.... originate from the Oquirrh Mountains and traverse the terrace. between tb. mountain. and the valley floor. 2.2 C~it,. De.eription Binlb.. Creek cuts tbroulh the northwe.tern COrner of the city, and Hida. Creek nearly p.r.llels the .outbern corporate limits. These Soutb Jordan i. located alon, the west bank of the Jordan River in .tre... u.ually flow duri:al .no.... lt and storm runoff. Irri.ation .outbwe.tern. Salt Lake County, in north-central Utah. The city has company policy allow. storm draiaa,e from new subdivisions to be an .ver.le elevation of 4,SOO feet and i. surrounded by .everal cbannel.d into the canal .y.t.... Con.equently, durinl periods of distinct terrain feature.. To tbe i_di.t. west are the Oquirrh beavy runoff, tb. intermittent .tre.... will carry the v~lume that Mountains, wo.e pe.k. ri.e to 10,000 feet. Twenty-five mile. to tb. canal .y.t... are incapable of hendling. This prOcess ha. been tbe nortb is tbe Great Salt Lake. To tbe e.st, .pproxilDately 15 adopted by Salt Lake County a. a flood-control ....ur •• _il •• aerO.. tbe v.lley floor, the W•• atch Mountains ri.e to South Jordan h••• n.twork of five major canale or ditche. flowing beiahts of 11,000 feet. Finally, Ut ..h Lake is located to the .outh i n tbe .outh-nortb direction. This aetwork con.i.ts of Provo in nearby Utab Count,.. Tbis lake i. tbe source of the Jordan River aDd ..,tie. into tbe Gr ••t Salt Lake. R•• ervoir C.nal, Utah Lake Distributin& C.nal, Ut.b and Salt Lake C.n.l, Soutb Jordan Can.l, and Beck.tead Ditch. Th ••e canals and ditcbe. divert water directly frota the Jord.n Riv.r ead .ad at Soutb Jordan i. ~rd.r.d by the City of West Jordan on the north, tbe Cities of Sandy City and Drap.r on tbe easc, the City of various point. in Salt Lak. County. Tbi. w.ter i. uled to fulfill liverton on tbe soutb, .nd unincorporated areas of Salt Lake County w.ter rilbt. and alricultural needs. A. IIIOre agricultural land in on tbe 'Outb and west. Soutb Jordan cover. an area of the valle,. i. developed into urban l.nd, len water vill ne.d to be approai.. tely 26.0 .quare _ile., 16.0 square miles of which are diverted fro. tb. river for farming. u.ed for alriculture (.-o.tly in the we.tern portion of the city). South Jordan i ••n area of mo.tly confined and shallow unconfined Anotber 9.4 .quare .ile. are u.ed for re.idential area.. The .quifer.. Ground water occurs in the uncon.olid.ted depo.its of r ...inin. are. i. u.ed for cOCllllN!rcial purpo.es. the Salt Lak. Valle,. under natural w.ter table and .rtesian condition.. In the lDOuntain area., so.. Iround vat.r seep. into Ia the Salt Lake V.lley, the Jordan River flood plains .re largely str... channels .nd flow. to t t. .!. Jordan River, and the remaining undeveloped. They do, however, cont.in some ••ricultural develop ground water move. throulh op.ning. in the b.drock, ev.ntuaLly ..ntt and a fev residence • • Recently, residential, indu.trial, and re.ching the Jordan liver. •• c ~rci.l developeent h••• hifted from the den.ely developed areas near Salt Lake City tovard the le.. er developed are.s of the Soils typically found in the terrace. are granular, while the • outhern and ve.t.rn portion. of the valley. vall.,. floor i. priIMrily compo.ed of cl.y. or clayey gravels • The Jor dan River is the .. jor vat.rway in Salt Lake County and the V••• tation r.nle, from conifer, a'pen, and oak. in the hilher

pr incipal .ource of vater for South Jordan. PrOli it. oriain at .-ountaia elevation. to .crub oak t lale t .nd underbru.h in t he lower Utah t.ke, the Jordan liver flov. 55 river mil.s northward to the .-ountain elevation.. Re.idential valley area. are v•• etated lUinly ereat Salt Lake. The Jordan River .r.dient i. approximately 5.2 with lawn .r••• e., Orn..... nt.l Ihrubbery, and shade tree •• feet per .il.. There ar. no .. jor tdbut.rie. to the Jord. n River Undevelop.d valley are.s .re atO.tly cov.r.d by Ir... e ••nd i a South Jord", bowever, a ••ries of diveraioa. and irri.ation ••••bru.h. A.pen and cottonwood tree. grov alonl the .tream canale act to deplete the river voluate durin. the s~r. South cour•••• Jordan it loc.ted n.ar the ar.a wh.r. tbe Jord.n River belin. to South Jordan ba •• t..,erate, s ..i.rid climate wi th four distin ,uisbable ••••on.. T.. p.rature. lenerally ranle from 10·' in the

4 /1 winter to 102°p in the l!Iun.er. Precipitation tends to vary directly with elevation, fro. 16 inches annually on the valley floor t o 40 Several roadway and railroad fill. on Dry and Willow Creeks afford inchea annually in the high lIIOuntains (Reference 2). U.Ilited detention atorage and reduced down.tre_ discharges a. conduit capaciti•• are exceeded. 2.3 Principal Plood Problea Officials of salt Lake County have estabUahed a Plood Control and Plooding in the Salt Lake Valley generally occurs due to three Water Quality Diviaion in their Public Works OepartJlent. It is typea of eventa, anow.elt runoff, cloudburst rainstorms. and general the r.eponaibility of thi. office to ..,.age and enforce develo~nt rainator_. S~lt flooda usually occur in April. May. and June. and flood-control ordinance. in the unincorporated areas of the Cloudburet rainstor. are high-intensity, short-duration storms county. 'lb. 4epartMnt alao works with the incorporated ~nties that uaually occur over a relatively aaall area. Theae storms are within th'.1 county, a. requ.eted, to ..nage and review flood-control cbuacterhed by high runoff peaka, but low volWDe8. They generally projects. Salt r..ke County alao baa a countywide flood-eontrol occur fro. June through October. General rainator... are caused by tax that enable. it to obtain fund. for use in construction of new low-intenaity, rainfall occurring over a longer period of time . flood control project. and ..intenanee of exiating facilitiea. Theae atoru can have a higher peak than the 8nowwtelt flood and a higher volu. than the cloudburat events. General rainstorms can OCCUr a t any tiJle. The history of Salt Lake County indicates that 3.0 IIIIGINBllRIHG JIIITIIalS flooding can occur fro. any of these events. However, the most dr_tic and extenaive flooding baa been due to anotnlelt and cloud Por the flooding source. atudied in detail in the ~nity, atandard bur at flooda. hydrologic and hydraulic atudy _tbOCSS were used to deter.ioe the flood haaard data required for thi. study. Plood events of a _9"itude which Significant s~lt flowa occurred in the area in 1909, 1912, ar. expected to be equalled. or exceeded .!!!5!. on the avera9. during any 1921, 1949, 1952, 1953, and: 1975. In the 1921 flood, the Jordan 10-, 50-, 100-, or 500-year period (recurrence interval) have been selected River had a ..an daily flow of 1,020 cubic feet per second (cfs) a. having epeeial .ignificance for flood plain ..nage .. nt and for flood at the Jordan Marrowa O.S. Geological Survey atre.. gage (No. inaurance pre.iUII rate.. 'l'he.e event., ~ly terMcS the 10-, 50-, 10167000), with an eatt.ated return interval of 20 yeara. The 100-, and 500-y.ar flood., bay. a 10, 2, 1, and 0.2 percent chance, .,.t notable flood on record in the Salt Lake Valley occurred during r ..poct1va1y, of being equalled or e.-..s during any year. Although April and May 1952. Thia flood waa cauaed by the rapid ..ltin~ of the r.currence interval r.pr•• enta the long ter. averase period between an unuau.lly l.rge anowpack 01"1 the W-!la.tch Mountains. The_an flooda of • specific ugnitude. rcre flooda could occur at abort int.rvale daily flow for thia flood waa 1,410 cfa, with an eatt.ated return or even within the ... year. '!'be r18k of experiencing a rare flood inter.al of SO yeara, and was alao recorded at the Jordan Narrows incr•••••• en period. 9r.at.r than 1 year ate con.idered. Por eXUlPl., atre.. gage. the riak of baving a flood which equals or exceecSa the 100-year flood (1 percent diance of annual occurrence) in any 50-year period ia approxi 2.4 Plood Protection Meaaurea ately 40 percent (4 in 10), and, for any 90-year period, the ri.k in cr.aae. to approxiaat.ly 60 percent (6 in 10). '!'he analyses reported Otah r..ke, at the head of the Jordan River, afforda a reduction of h.re r.flect flooding pot.ntiala baaed on conditions exiating in the floodflowe along the Jordan River above 2100 Street South. This ~uni ty at the tiM of oc.pletion of thi. atudy. Mape and flood eleva lake h • natural water body that has been artificially -=>4ified tiona .ill be ..oded periodically to refl.ct futUre changee • .a that the water-aurface elevation can be controlled through the u.. of ..veral large radial gates and. a puaping atation. The ability 3.1 Bydrologic Analy... to rai .. and lower the lake elevation caused conflicts between the .ater u.s.re and the property owners adjac.nt to the lake. To reeolye Bydrologic analye.a were carr ied out to eatabUah the peak diacharge the conflicts, a -cc.proai •• level,- on elevation of 4,489.34 feet, frequency relat10nahipe for flood. of the .elected recurr.nce wa. agr.ed on in 1885. Whenev.r runoff forecaats indi cate that intervals for each flc:oding source etudied in detail affecting the the ••tar aurface .Ul exceed the co.pro.ise level, the lake 18 ~nity. drawn down to per.it diecharg•• co.parable to natural Conditions. Several etre.. gage. have been operated by the City of salt r..ke A nu.ber of irri9ation diverdona alon9 tha Jordan River near the City and the O.S. Geological Survey on count}" .tr.... dnc. the south.r", boundary of Salt Lake County, .uch a. Turner DaJI at Jordan begiMlr'9 of the century (Refer.nce. 3 and 4). 'J'b. O.S. Geological ..rrowe, can eub.tantially reduce floodflowa. Mo.t outflow fro. Survey baa operated .tre_ 9ag. Ro. 10167000 at Jordan Marrawa Otah X.k., ezcept &lri"9 perioda of high flow, can be diverted to dnce 1913 and alao ran a .tre.. gage at 9400 South Street (Mo. th... canolle. 10167200) frOli 1965 to 1968.

6 Bxisting atreaallow information is not adequate to predict cloudburst runoff values downstream of the canyon mouths, vhere flows depend on inflow tra. the urban area. To obtain flow values for Dry and Willow Creeks, the u.s. Army Corps of Engineers HEC-l computer runoff .adel vas used (Reference S). This model uses a kinema tic vave calculation to produce runoff due to rainfall. The model ~tes and routes flows based on physical characteristics of the ba.in (such as percentage of imperviousness, infiltration rates, basin area, and slope) and storm characteristics (such as precipitation depths and rainfall distribution and duration). Rainfall depths were obtained frc. Precipitation Frequency Atlas of the western United States, Volume VI, prepared by the National Oceanic and At.ospheric Aa.inistration (Reference 6). Because of the lack of available rainfall-runoff data, it was not possible to calibrate the oo.puter model.

Peak d1echarge-drainage area relationships for each stream studied in detail are shown in Table 1.

3.2 Hydraulic Analyses

Analyses of the hydraulic characteristics of the flooding sources studied 1n the oo..unity vere carried out to provide estt.8tes of the elevations of floods of the selected recurrence intervals along each of these flooding sources. water-surface elevations of floods of the selected recurrence intervals for the detailed studied strea.. vere oo.puted using the O.S. Ar8y Corps of Engineers BEC-2 step-backvater ~ter prograa (Reference 7).

Cros. section data for Dry and Willow Creeks were developed by the O.S. At., Corpe of Engineer. for the 1974 Flood Plain Infor.. tion report (Reference 8). Cros. sections vere taken fra. topographic asps at a scale of It600, vith a contour interval of 4 feet (Reference 9), suppl... nted bf additional survey data provided bf the county. SUpple.. ntal cro.. section. to define new bridges or chang.s in topography vere -.de as a part of this Plood In.urance Study. All bridg•• , da.. , and culverts vere field checked to obtain infor ..tion to de.cribe their structural 9eo~try. Location. of sel.cted cro.. section. u.ed in the hydraulic analyses are 8hown on the Flood Profiles (Exhibit l). POr strea. s~nt8 foe which. floodway i. ~ted (Section 4.2), .elected cross ..etion location. are also ahown on the Plood Boundary and Floodway Map (Bxblblt 2).

Channel roughnes8 factor. (Manning's -n-) used in the hydraulic oo.putation. vere cho.en by engineering jud~ent and ba.ed on field obeerv.tion. of the .tr.... and flood plain area.. Roughness values ranged fra. 0. 030 to 0.040 for ..in channel. and fra. 0. 040 to 0.060 for overbank ar ••••

B !y Table 1. Summary of Discharges

Drainage Area Peak Dischargea (cubic feet per second) Ploodina Source and Location (SQuare miles) 10-Year SO-Year 100-Year SOO-Year

Dry Creek. At 700 Eaat Street (upatream of South Jordan) 13 At 300 West Street 14 Willow Creek At 12300 South Street (weat of Interltate Highway 1S, uPltream of South Jordan) 17 lSI no1 2761 9221 Jordan liver Marrovs 2,1S5 1,260 2,400 3,000 4,800 9000 Soutb Street 2,905 1,170 2,230 2,790 4,465 saoo South Street 2,985__ 2 1,200 2,280 2,850 4,560 Litt!.e Cottonwood Creek Confluence __ 2 1,585 3,010 3,740 5,925 Iii Cottonwood Creek Confluence __ 2 1,930 3,665 4,535 7,145 Mill Creek Confluence 2,000 3,800 4,700 7,400 2100 Soutb Street 3,1653 2,000 3,800 4,700 7,400

1Dilcbarle Qedu~tion. are due to Overbank Storase (generally, a result of construction 1n the floodplain) and/or Loaael to Canal a and Irrigation Syatema 2o.ta Mot Available lvalue Eatimated Baaed on Publiabed Draina.e Area for Caae at 1100 South Street

~\ Stllrting vater-aurface elevations for all atreaas were determined by nor_I depth e.lculati~a. 100-year flood boundary haa been abown. s.all area. within the flood boundaries _y lie above the flood .l.vationa and, th.re Plood profiles were drawn showing c:::c:.p.lted water-surface elevations for., not be .ubject to flooding, owing to Iblitation. of the _p to an accuracy of 0.5 foot for floods of the selected recurrence sca1., auch ar.aa ar. not shown. iDterval. (B:dIibit 1). 4.2 Ploodw.y. fte hydraulic analyses for thi. study were based on unobstructed flow. It ahould be noted that flood elevations shown on the profiles Bncroacm-nt an flood plain., aucb a. artificial fill, reducea the are ocnsidere4 valid only if hydraulic .tructures reuin unobstructed, flood-carrying capacity, incr••••• the flood heights of strea., operate properly, and 60 not fail. and incr••••• flood baarda in ar.aa tt.y0n4 the .ncroacm.ent itaelf. One a.pect of flood plain UM9_nt Involv•• balancing the econo.io Approxiaate flood depth. for the Jordan River, upstre.. of the gain fro. flood plain develos-ent againat the re.ulting increase IIOrth Jordan canal Diversion Daa, were deterained using the O.S. Array in flood haaard. Por purpoaea of the Rational Plood In.urance COrps of Engineer. BBC-2 step-backwater COIIpUter prograJI (Referenee 7) . PeogrD, th. concept of a flooc!way is u.ed aa a tool to a ••ist local ~nitie. in thia aapeot of flood plain aanag... nt. Onder All el.vationa are r.f.renced to the National Geodetic V.rtical this concept, the ar.a of the 100-y.ar flood ia divided into a D1ta of 1'2' (lCVD). nevation refer.nce ..rks uaed in the study floodway and a floodway fr inge. 'l'tle floodvay is the Ch.M.l of a are shown on the ..pe. att... plus any adjacent flood plain ar.aa that ....t be k.pt fr.e of .ncroachMnt 1n order th.t the 100-y.ar flood _y be carried without aubatantial incr••••• in flood height.. Kinbl_ standards 4.0 rLOOD PLAIR _ APPLICMIOIIB of the Pederal _rgency Manag_nt Ag.ncy lia1t .uch incr.. s.s In flood beight. to 1.0 foot, provIded th.t hasar60us v.locitiea ar. '!'he Rational Ploodi Inauranoe Progr .. encourag.s Stat. and local goverMlenta not produced. '1'be floodvay. in this r.port are preaented to local to adopt .ound flood plain aanag... nt progra.. 'l'tler.fore, each Plood agencie••• ainiaua .tand.rd. that can be adopted or that can be Inaurance Study include. a flood boundary up designed to ..stat ~ni used a. a baai. for additional .tudi••• tie. in developing 80Und flood plain aanag... nt ..aaures. All tloodw.ya orlIIPUted aa a part of this .tudy were deter.ioed on 4.1 Plood Boundarie. the baat. of equal-conveyance reduction fra. .ach aide of the flood plain. 1'he r ••ulta of th... cc.putation. wer. tabul.ted at Hl.cted In order to provide a national standard vithout regional d1acri.ina cro.. Motions for each .tr... aegMnt for which a fl.oodway vas tion, th. lOa-year flood has been adopted by the Ped.ral Eaergency c:c.pute4 (Table 2). Mana~nt Aqency a. the ba •• flood for purpoa•• of flood plain Mnag_nt ....ur... 'l'tle SaO-year flood is etlPloyed to indicate As shown on the Plood Boundary and Ploodway Map (BlEhibit 2), the a&Utional area. of flood ri.k in the oo.aunity. Pol' each atrea• floodway width. were det.r.ined at cro.. sectiona, between ero•• • tudied in detail, the boundar i •• of th. 100- and 500-y.ar floods aection., the boundar i •• were int.rpolated. In caa•• wh.r. the have been delineated u.ing the flood .levation. deter.ioed at each boundaries of the floodway and the lOa-year flood are either cloae cro.. section, tt.bteen cro.. aection., the toundari •• vere int.r tog.ther or collinear, only the f100dway boundary hal been shown . polated u.ing topographic ups at SCIIl•• of 1 124,000 and 112,400, with a contour int.rval of 5 feet (Ref.renc•• 10 and 11). 'l'be ar.. tt.breen the floodway and the boundary of the laO-year flood is t.raed the floodway fring.. 'l'he floodvay fringe thua Approxiaat. flood boundaries for the Jordan River, uPlltr... of the enoc:.pa.... the portion of the flood pl.in that cou14 'be cc.pletely IIOrtb Jordan Canal Di"'.raion DaJI, weI'. d.lin•• ted udng the 1 ~ 2 4,000 ob.tructed without increaaing the wat.r-surfac. elevation of the SCIIl. topogr.phic ..ps diacu ••ed pr • .,.iou.ly (Referenoe 10) . lOO-year flood .,re than 1.0 foot .t any point. Typical reletion abipai tt.twHn the floodw.y and the floodvay fr i nge and their signif Approxiat. flood boundar i •• in ~ portion. of the .tudy a rea lcance to flood plain dev.lo~nt are shown in Pigure 2. wre tIIt.n fro. the Plood liliAI'd Boundary ...p ,lIef.rence 1) .

Plood boundar i •• foe the 100- And 500-y.. r flood. are shown on the .lood Boundary and Pl.oodway ...p (bhibit 2). In ca••• where the 100- and 500-year flood boundaries ar. l,.. l OH tog.th.r, only the

10 11 17 BASE FLOOD F!.OOOWAY FLOODING SOURCE WATER SURFACE ELEVATION SECTION KEAII WIDTH AREA VELOCITY REGULATORYr I FLOODWAYWITHOUT JFLCX)OWAY WITH I INCREASE CROSS SECTION DIST....d- (FEET) (FEET p~ (~ SE<'ONO (FEET NGVD) Dry Creek A 5,325 48 151 2.8 4,340.6 4,340. 6 4.341.3 0.7 8 5,830 35 126 3.3 4,3U.6 4,344 . 6 4,344.8 0.2 C 6,290 60 166 2.5 4,346.2 4,346.2 4,346.7 0.5 0 6,700 36 91 4.6 4,346.7 4,346.7 4,347.5 0.8 B 7,330 36 96 4.4 4,351.4 4,351 . 4 4,352.2 0.8 F 7,818 160 939 0.4 4,358.9 4,358.9 4,359.8 0. 9 G 7,920 57 256 1.6 4.358.9 4,358.9 4.359.8 0. 9 B 8,760 92 201 2.1 4,360.5 4,360.5 4,361.2 0. 7 I 10,130 38 107 3.9 4,369.3 4,369.3 4,370. 1 0.8

Willow Creek A 1,000 16 35 7. 8 4,317.9 4,317.9 4,318.2 0.3 8 2,260 5 26 10.7 4.339.1 4,339.1 4,340.1 1.0 C 2,560 30 67 4.1 4.344.4 4,344.4 4,345.2 0.8 0 3,360 60 190 1.5 4,351.3 4,351. 3 4.352.2 0.9

1 Peet Above Mouth

...,. FEDERAL EMERGENCY MANAGEMENT AGENCY FLOOOWAY DATA ... CITY OF SOUTH JORDAN. UT ISALT LAKE CO.) -... DRY CREEK·WILLOW CREEK N 1;2... FLOODING SOURCE FLOOOWAY BASE FLOOD WATER SURFACE ELEVATION

WITHOUT Krnoo IIlGUlA I QIIY M" IfrK!UAY Wl01H VU....OC/TV I HOOOWA' HOOOWAY (M)5S WOfON OISTAI

Ipeet Above Surplus Canal Diver.i on

T A FEDERAL EMERGENCY MANAGEMENT AGENCY FLOODWAY DATA •l CITY OF SOUTH JORDAN, UT E , (SALT LAKE CO.) JORDAN RiVeR 13 5.2 P100d a..erd P.cton (PHP.) fl ...------tOO,Y EAR F LO OD PLAIN ------....,,1 The PIlI' h tbe reelera1 a..r.eacy MeDa ....nt Aaency device u.ed to correlate flood inforaation 'lith in.urane. nte table •• Corr.lation. bet.... n property cl ....e frCHI flood. and their PHP are u.ed to .et actuarial inlurane. preaium rate t.ble. based on PBP. fr.. 005 to 200.

The PIIP for a r ..ch i. tbe av.ra.e wei,btld difference between the 10- ead 100-year flooel vater-Iurface el • .,ation ••aprelled to tbe roea ....t one-balf foot, and ,boWD a. a three-digit code. Por ....,11, if the differece bet.... n vater-Iurface elevationl of the 10- eael 100-year floodl h 0 . 7 foot, tbe PHP il 005; if the difference it 1.4 feet, tbe PHP it 015; if the differenc:! i . 5. 0 feet, tbe FRP i. 050. When the difference between the 10- and 100-year vater- .urflce elevation. it ,reater than 10.0 feet accuracy for the PHP i. to tbe n.are.t foot. '

5.3

LINE "'8" THE FLOOD ELEV ATION BE FOR I! ENCROACHMENT. .ut~r tbe detemination of reache. and their ra.pectiva PHP., the LINE CD IS THE FLOOD ELEVATION AFTEA ENCROACHMENT. . SU~HAAG E IS NOT TO E X CEED 1.0 FOOT 'FEM ... AEDUIAEMENTI OR L. ESSEA A MOUNT If ' ,"le .FIED BV STA TE . entue incorporated area of tbe City of South Jordan va. divided into zone., eacb havin, a lpacific flood potential or bazard. I'igure 2. Ploodway Scb_tlc lach zone val •• liped ODe of the foUovin, flood in.urance aone de.ipation.,

Zone Al 5 . 0 xaUM*Z APPLICM'ICB Special Plood aa.ard Areal inunelated by tbe 100-,..ar flood, detemined by In «del' to ••tabl1* actuarial iMUrance rat•• , the Pedel'al _rgency approaiute _tbod., no ba.e flood lIane9~t Aqency hae ct.v.loped • proce.. to tranaforll the data fro. the elevation•• hOVD or PHP, deterllined. 4Ift91neering atudy into flood inauranoe criteria. '!'hi. proce•• includ•• the 4eteraination of reach•• , Flood HaUird Pactor., and flood insurance Zone. A.3 and AS I Special Plood Haaard Area. i nundated :10M &.. lgnationa to!: eacb flClOding IlQUrc;:e atudied in detail affecting by tbe 100-year flood, deterllined by Sooth Jordan, UUb. detailed _tboel., ba.e flood elevationl IhoWD, Ind aone ••ubctivided Iccordin, to PH".

...eb •• are cSefl"!1'd .. length. of watercour ••• having relatively Zone 8 1 Ar.a. between the Special Flood a.aard the __ flood baArd, baaed on the a.erage weighted difference in Ar.a. and the liaitl of the 500-y.ar water-llUrface ele.ationa between the 10- and lOO-y•• r floods. '!'hi. flood, includin. a rea. of the 5!J0-y.ar difference cIoit. not have • variation greater than ~t indicated flood plain that ar. protected frCMI in the following table for .,re than 2:0 percent of the re.ch I tbe 100-year flood by dike, levee, or oth.r vater control Itructure; aho A.erage Difference Between ar••• lubject to certain type. of 100- 10- end lOO-Y.. r rloo4. y.ar .haUov flood in. where depth I are le .. than 1.0 foot; and Ir.a ••ubject Le.. than 2: f ..t 0.5 foot to 100-y•• r floodin. Eroa .ource. vi tb 2: to 7 f ..t 1.0 foot drai na •• areal l e .. than 1 I quare 7.1 to 12 f ..t 2:.0 f ..t aile. Zone B i. not .ubdi vided . lIOre than 12 feet 3.0 f ..t

14 _'0 future floo~ ~O"~I. The reaultinl report (Reference 18) propoaed lOne C. Are •• of .lniu1 flooding. cbannel IDOdLflcauoDI on the Jordan River, a flow control Itructure for Utah Lake, and a plan for reaulatina Utah Lak~ outflows. The.e propol~h ver~ b&1~d on delian diacharle valuel eltablished through an analynl of h~ltot'1~al Jordan liver and tributary floodflow record. and a .yn~be81~ of Lllpactl of controlled retea.es froll Utah Lake. The.e de81~ duchar.e~ are .hown in Table 3. The design diacharles 5.4 Flood Insurance Rate llap Deacr ipUon vere u.e~ Ln a ?ydt'auhc nap-backwater IDOdel (aeierence 7) of the Jordan RLv~r wbLCh ~"UM.d all propo.ed channel IDOdification. to be in 'lb. nood Inaurance Rate Map for South Jordan is, for inBurance pl~ee. Tb.1I analY811 re.ulted in a water-.urface profile shown in purpo... , the ~lnclP11 r ••ult of the Plood Insurance Study. 'Dlis thu Plood Inauranee Study aa tbe Utah Lakel Jordan liver Flood _p (publ1.. ., ..parataly, contain. the official delineation of Mana~.. nt Plan Profil.a. Vo Cotiparieon or correlation between theae flood tnaurance .one. and be •• flood elevation linea. Baae flood ~rofLle. and the data pre•• nted in thia nudy can be IUde or ia el••• tion 11... 1Ib0lf the location. of the expected whole-foot water Lntended. Moat of the Jordan liver channel IDOdification. and the Utah wrface ele.ationa of the bea. (lOO-year) flood. 'D\ia up is Lake Outflow con~rol .tructure bave not been completed. The proposed developed In accordance with the lat.at flood inaurance up plan for regulating outflows frOil Utah Lake is not being used at preparation guideline. published by the Pederal z.erqenc::y Management preaent. Agency. Tbie study ia autboritative for the purpoaes of the aational Plood Inluranee Progr... ; data presented herein ei ther supersede or are 6.0 0'l'IIIIIt 82001_ coepatible with aU previoul deterainationa.

Flood Jnauranoe StueU•• ue being prepared for the adjacent Cl tiea of 8aJxIy City ( ..ference 12), Draper (Reference 13), and the unincorporated 7.0 LOCATIO!! OP DATA ar••• of Salt Lake County ( ..ference 14). '1'hia study ia In agre_.nt with tile.. Flood Insurance Studi••• Info!'lll.tion conee~inl the perthent data uled in preparation of thia study can. ~ ~btaLned by contacting the aatural and Technololical r •• i. A teed I'lood saurd Boundary IIIIp being prepared for the adjacent. HaEards D1VU10D, Pdderal s..r.ency Mana.etMnt Agency, Buildinl 710, City of ..at Jordan ("fe['ence 15'. A Flood Insurance Rate Map 1e being Denver Federal Center, Lakewood, Colorado 80225. prepel'ed for tbe a4j.aent City of Riverton (Reference 16'. Flood boundal'ie. MCMl an tho.. _~ an in agrHlleftt with flood. boundariea mown in thi. Flood In.urance Study. 8.0 BIBLIOGWHX A!ID MPIRB!!CBS

!trie D.S. Arwty Cor~ of Bngineer. rlood Plain Infor_tion report for Midvale 1. U.s. Depart_nt of Housina and Urban Developatent Federal Draper, utah (Reference 8) included analyses of Jordan abel' and Dry and Insurance AUiniltration, Plood Ha,.rd Boundary Map. City of willow erHk.. Becau.. of the reviaed hydrology and additional topographic South Jordln. ~, Scale h 12 000 July 26 1974 R . d infor_tian ueed in thi•• tudy, it supersedes the Pl00d. Plain Infor_tion January 30. 1976 "" evue report. 2. City of South JardIn, Utah, aaaie PIt. COUee:tion, undated Di.cbarge. fro. a .tudy by the U.S. Al'1IY Corpe of Bngineer. (Reference 17) weI'. utiUaed for the Jordan River durift9 the couree of thi ••tudy. 3. U.9. Depart~nt of the Interior, Ceological Survey, Water Supply Paperl, Kaapltude and ~re9u.ncy of Plooda in the United State •• '!be recs.ral _rgency lIana~t Agency previously publhhed • Plood Part 10. The Creat Ballg, tbroulh 1963 a. ..r4 Boundary Rap f« the City of South Jordan (Rllf.rence 1). This _p ... ueed a. the KlUrce for ... approxiaate flood boundarie. for 4. U.s. Depart_Dt of the Interior, Ceololical Survey, !Y1s.I. thi. nood In.urtlftCe Study. 'l'bla atudy repre.enta a .,re recent and aesourclI Ott. for Utah, 1961-1975 ~eben.i.. analy.i., ther.for., it auper..se. the Plood aaurd Boundary Mop. U.S: De~rt ..nt of the Ar!Dy, Corp. of Kngin,era, Hydrololic KnlLneerLnl Center, CoeDuter ProlrllD 123-X6-L2010. HKC-l Flood I'ollc.ing the di ...trou. flooding alOl19 Dtah Lake and the Jordan River Hxclro'raph lKYu, Davia, CAlifornia, 1979 in 1983 and 1984, Salt Laka COunty and Utah COunty official. co.Iis.ioned an in".1;igatic. by CII2Il BILL, Inc., of r • .edial ....ur •• to .iUgate

17 16 Table 3. Jordan River Propo.ed De.ign Di.cbargel

Loc.tion De,i.n Di,eb.rl. (cf,)l saoo Soutb Street (Bullion Street) to 9400 Soutb Street 3,330 9400 Soutb Street to Jord.n Harrow. 3,260

lSource of Di.cblrae Data: Utab Loke/Jordln River Flood Htn,,'!!nt Pl.n. Pb ••e I Report (I.f.r.ne. 18)

I~ 6. U.S. Depart_ot of Co-.erce, National Oceanic and Atmo.pheric AdIIinhtratioa, Precipitation 'regueae! Atla. of the Western lIIIll.U. lliW. Vol .... VI. 1973 21. U.S. Depart_nt of tbe Araty, Corp" of !nlin•• rs, HydrololY. 7. U.S. Depart_at of the "f"IDY, Corp. of Engineer!l , Hydrologic (I.vie.d) Jordap liv.r Inveltil.ti" n. UQP'r Jordan River tnterim ~. 1984 I!nlineeriol Center, Co_outer Proar_,. 72J-X6-L202A. H~C-2 Water ~ EI..e.filn, Davis , California, November 1976 w1th Updates 22. Aero-C-r.pbic., Inc., Orthophoto Topolraphic M.p.. Jordan River 8. U.S. Depart_at of the "f'1DY, Corp. of Engineers, FLoodplain fr. 2100 Sout.h t.o tbl Ut..b CountY 1.ine. Sc.le 1:4.800. Contour Info!'1lltion. Jordan River Complex II. Midvale-Draper. Utah, 1974 IDt.rval 4 fe.t witb 2-foot .upRl ....mtal sontour., November 1990 23. 9. Caldwell, Richard. and Soren.on, Inc. , Topographic H.p •• Jordan U.S: Dep~rt_nt of tbe Aray, Corps of Engineer., Hydrololic River. Dry. Willow ••ad Corner Canyon Creeks, Scale 1:600, KnIID •• nn, C.nter, HlC-2 Water Surf.ce Profi le. CO!!put.r Contour Interval 4 feet, Kay 1972 lI2&ua, V.rtiOD 4.6.2, Kay 1991, Witb Pull Micro-Ca.puter IlIpl... ntation by H'eatad Method., HMVerlion 6.41 10. U.S. DepartlHDt of the Interior, Geological Survey, 7.'-Minute 24. Serie. Topographic Map., Scale 1:24,000, Contour Interval 5 feet: U.S: Dep.rt_nt ~f the Int.rior, Ceololic.l Surv.y, 1.5-Minute Midvale, Utah (1963), Photorevi,ed (1969 acd 1915) Sen •• Topo'rapble MlP', Scale 1:24,000, Contour Interv.h 5 and 20 feet: Sa~t Lak. City South, Utah (1963), Pbotcrevised (1969 11. Aerograpbics, Inc., Ortbophoto Topolt'aphic Maps. Dry Creek and and 1915); Mldvalt, Ut.h (1963), Photor.via.d (1969 and 1915); Willow Creek, Scale 1:2,400, Contour Interval 5 feet, March 1916 JordAD ..arrow., Utah (1951), Photor.vi.ed (1969 and 1975) 25. 12. Federal Emer ••ney Mana._nt Aaency, Plood Insurance Study. City ,!ro-Craphics, Inc., Orthopboto TOP9'tlphie Mlp. of W•• t hU.! tlh of SADdy City. utah, unpublished CUT' U , Seal. 1:6,000, Contour Int.rval 5 fe.t prepared for W.1t. Vall.y City, April 1985 ' 13. 'ederal "-rl!Dey KaIlaI_nt Aaency, Flood In.urance Study. City of Dranr. UtM, unpub1hhed Barn.tt, J.A., Croupdyettr 8ydro10ly of l!ilJ:ltion Cagyon. SIlt 14'" Coupty. utah, Utah State !alin•• rs Office, Jun. 1966 14. Federal r..erl.ncy Mana._nt Aaency, Flood Insurance Study. Salt Lake Coupty. Utlh (Unipcorporated Ar, •• >, 1985 Biallhal Inliae.rinl, lugoff !atiMtI. in !!Iilration Canyon, 1979

15. ,.d.rll e-rlency Manal_nt Aaency, Flood Hazard Boundlry Map. Borlquiat, I.S., Utah 4'" - Jorde liv'r I'port, 1947 City of W.1t. Jorde. Ut.h, Scale 1:12,000, unpublished Caldwell, .ic~rda and Soran.oD, Inc., Ortbophoto Topolr'phic 16. Federal "-rl.ncy Man'lellent Aaency, flood In.urlnc, Rate Hap. tIIaL. JordlA bytr, Seal. 1:1,200, Contour IDterval 2 Peet City of Riverton. Utah, Scde 1:6,000, unpubli.hed Decaber 1966 '

17. U.S. Depart..nt of the Army, Corp. of Enlin.en, JardIn River Caldwell, lichards and Soren.oD, Inc., Salt. Wk. county Mauer Ipveuicltion. utah, 1980 W.t.r. 1..,1' lAd Stom Drain'I' PIM, 1971

18. ca2M HILL, Inc., utah Lake/Jordln River flood Mana • .,nt PrOlra•• ca2M HILL, ~ordM lint SYTYIY MODUMD" 2100 South to 14600 Ph.a. I R'port, .ubaitted to Salt Lake and Utah Countlet, 1984 12!!t.Jl, Sut.1tttd to S.lt Lak. County Plood Control S.... t ••ber 1987 • ~ 19. U.S. Depart.. nt of the Interior, Geological Survey, Interagency Advi.ory Coc.ittee on W.ter Data, Bulletin 178 of the Hydrology ca2M HILL, UtAh 14k. - JordAn Riv'r Plood NtDa'IMDt Prolr... Subc.o..ittee, Cyidelipe. for Dtterllinin. Flood Flow Frequency, Pha ~ . I R'port, 1984 aevi ..d Septaber 1981, Editorial corr.ction March 1982 ~ov, V.n T., Iftadbook of AppU,d Hydrolon, N." York: McCraw- 20. calM HILL, Inc., Hydrololy leport of • Dtt.il.d Flood In.ur.nce 8111 80011. Ca.pany, 1964 StudT for the Jord.p liv'r in Salt Lak. Coynty. Ut.h, prepared for rDCA, 1991 Chow, Ven T., Optp-CbtnD.l Hydraulic., NIV York: McCraw-Hill Book Ca.pany, 1959

19 20 Craddock, D.W., Salt Lake City Flood. 1945, Proceedings of the Utah 4cld_y of Scienc •• , Art. and Letter., Volume 23, 194~-46, pp. 51-61 'arD.ll, P.!., CO!!put'I Si!Ulation Mod.l - Description and Users tIIIUlIl, gept ..ber 1975 Denver Regional Council of Governments, Urban Storm. Drainage tIImlIl, Volwae. 1 and 2, 1969 Roberts, 9.H., Ptt'raination of Re,."ion Hydrolraph. and l2u.i2lJ. Applications Edvard. and Kelley-Western, Con.ulting Engineers, A Haster Plan for Control of Surface Storm W.ter. Salt Lake City, July 1960 Rollins, Brova, .nd Cunell, Inc., Cau". of Floodinl within Salt Lake VaUey. Utah, 1979 Evan., R.W., An Analni. of Salt Lake City's 1952 Flood, University of Utah, 1953 Rollin., Brovo, and Cun.ll, Inc., HydroloRY Report of Flood Ip.ur.gce Studi •• for Sel.ct.d COMUQities in. apd the Panter, E.E., and J.E. Pletcher, Distribution of Predpitation in Upincorporat.d Area. of Salt Lake County. Utah, 1980 Mount.inou. Areas, World Meteorological Organization, Geilo SyaPOIiWl, Norway, July 31-Aulullt 5, 1912 Salt Lake City Water Department, 1916 y;tah Lake Stas.-Di"hlrce Curve, Drawina 24, Pile 28, Humber 11347 Forsgren A"ociatet, P .A. , A,rial Target Coordinate and Elev.tion Li.t for JordlD River Aerial Happing Proiect from Salt Lake City Water Department, Oiler.s Shovine Pluctuations of Jord'g ".rrow, to 2100 South Street, 1991 Utah Lake, Dr.vina 2, Pile 28W, 1900

Cardner, Br.d, 1989 Ut.b Lake - Jordan River COIIIDi"ioners Annual Salt Lake City Water Depart_nt, DialEY ShowinR Pluctu.tions of ~. 1990 Vt.h Lake, Dravina 49, File 28W, Nuaber 4948, 1915

Cin,et"y A.sociates, Inc., Hydrology Report - Flood In.urance Salt Lake City W.ter Department, Pluctyations of Utah Lak•• RYsl!u.- 20 Utab COllllUnitie •• FIA Contrast H-4790, October 1979 1900-1920, Dravinl 54, File 28W, NWIlber 6662

Cline., W.P., Cloudburn Plood. of Salt Lake'. !aft Bench 1900- Salt Lau County Depart_ftt of Public Work" 'lood Control 1960 (M Anlly.i. of tbe Contributins Factor.>, University of Division, StnMfloy apd Precipitatiop Oat. Report. Jordan River Utab, June 1970 Tributari'" S.parat. book. for ••ch v.t.r year, 1983-1989

Hoehcber, 1:., and B. Clenne, Salt Lake Valley Intensity - Salt Lake Count,. W.t.r Quality and Water Pollution Control, Salt R,yution Frequency Curve •• Partial Duration Series, Univenity of Lak. County 208 Study, Area-Wide Water Quality Man,cement Phn, Utah, 1979 1978

Houpton, J.G., Cbar.cterittic. of Rainfall in the Gre.t a.sin, SODDtal, C., and B. Clenn., RAinfall Inunsity - Duration University of Nev.d., De.eret Rue.rcb Institute, 1969 Prequ.ncy ~, University of Utah, 1978

l Kin" H.W., and !.P. Brater, Itins • H.ndbook of Hydraulics, 5th St.t. of Utah, Fifth Bienni.l Report of the State Enline,r of !cliti on, New York: McCraw-Hill Book. Comp.ny, 1976 !I1IIl. 1905

Linsl.y, R.It. Jr., et.at. Hydrolosy for Enline.r., McGr.w-Hill State of Utah, Third Biennial Report of the State Enlin,er, 1901 Book. Co.-pany, 1982 aDd 1902 lIiehon and Mazvell, Con.ultinl Engineen, Plood Control Pl.n Svanson, C.L., R.tid.ntiat Floodine in Bench Are•• in Salt Ltk. !lIia& Dtt.ntion a'dns, report prep. red for Salt Lake County Coup,y. U,.b, 1968 Ca..i .. ioners, 1971 V.S. Depart_nt of Aariculture, Precipitation Ch.r.curittics of Pac ~. r, P.!., and B.D. Willi ..s, Loelinl and Pre.cribsd Burnine SwatI' 9tom .t; High El.vat;ion 9tations in Utah IUJcts op tbe Htdrologi, and Soil St.bility Behavior of Larch/Doualas Pir Por.stt in the Nortbern Rocky Mountains, 1974

21 22 U.S. Depart_nt of Aariculture, Office of Eltperimental Station!, "POrt. of Irri'ltioo Invelti.ation. in Utah, Bulletin No. 124, u.s. Depart_ot of the Any, Corp. of !nline.n, HydroloRic 1903 !alin•• rinl C.ot.r. Training DocUMnt 110. 5, ll9.2A!!n Dtt.raiMdoQ Ulipl cO!!put:.r Prolry HIC-2, May 1974 U.S. Depart_nt of qriculture, Forut Service, Re.eareh Paper ~. 1971 u.s. DepartMDt of the Army, Corp. of Enlineen, Hydrologic Inlin•• rinl C.nt.r, Trainin; DoCu.8Dt 110. 10, Introduction and U.S. Depart_nt of Aa;riculture, Soil. Conservation Service, Applisatiop of lip_dc Wave Routin. T,sbniqu" Utin. H!C-t "HydroLogy," 1I.tion.l Enlineerinl Handbook, Section 4, 1972 Davi., California, 1979 '

U.S. Deptrt-.a.t of qricu1ture, Soil Conaervation Service, Soil u.s. Depart_nt of C~rc., Weather Bur.au, Memorandum, Severe Surv,! of S.lt Lake Arel. Utlh, 1914 HlihtoA at Salt Lek. City. AUBU't 194), 1945

U.S. Depart_ot of Ag:riculture, Soil Conservation Service, Soil U.s. Depart_nt of C~rce, 1Iation.l Velther Service, ClilMt. of Survey and Interpretation. of SWlllDit Soil Survey Area. Wasatch Salt Lay City. Utah, 110M T.chnical MeatorandWD NWS WR-152, 1989 Mountain Portion of S.lt Lake County. Utah, 1975 u.S. Depart_ot of the Interior, Burea" of Recl .... tion, De.iBn of U.S. Department of qriculture, Soil Conservation Service, SMU Dam., 1974 Technical Rele•• e 110. 55, Urban HydrololY for Small Watersheds, 1915 u.s. Depart_Dt of tbe 10t.rior, C.ological Surv.y, Water-Supply Paper 994, Cloudburtt: flood. in U,th. 1850-19l8, 1946 U.S. Depart_nt of tbe Aray, Corp. of !naineers, Draft featibility Report fDd Draft EnvironMntal Impact Statement. U.s. Depart_nt of the Interior, C.olOlical Surv.y, V.ter-Supply upptr Jorclap liver Interi. Inv,.thation Ut.h, 1987 P.~t 1314, COIIpilat:ion of Record. of Surface Waten of th. Ua.llI.!l StU" throulh S'Pt:wbtr 1950. PaU 10. The Creat k.in U.S. Deptrt_nt of the Aray, Corp. of !naineers, Flood Flow 19S6 • 'r'qUlpcy Wly.i., Ce:ner.li&ed Cotaputer Proar.. 72J-X6-L7550, 1982 U.S. Depart_Dt of the Interior, C.oIOlical Surv.y, Water-Supply Pa~r 1714, eovilation of R.eord. of Surfac. WAt:.r. of the U.S. DepartMDt of the Aray, Corp. of !nlin.er., UORubli.hed llall.U Stat••• Oct:0ber 1950 to S'Pt:.ber 1960. Patt 10. The Cr.a: '1004 Pr'q"ency C"rve. of th. Jordan River, 1985 kIia. 1963

U.S. Departant of the AraIJ, Corp. of Engineer., Interim S"rvey u.S. Depart_nt of the Interior, C.oloaictl Surv,y, Water-Supply R.port for Flood Cootrol on Jordan River B•• in. Salt Lake County Paper 1260-8, flood. of April - Jun. 17)2. in Ut:ah and Nevada Str..... Utah. Appendix A-Hydrology, June 1910 19S7 •

U.S. Dep.rt.. nt of the Anay, Corp. of Enaineer., Hydrology De.iln U.S. Dtpart.. ot of tb. Interior, Ceological Survey, Flood. in M..arandum 110. J, Little Dell Lok •. Salt Lake City Str..... Utah, ~ KalRityde and FrequeDcy, 1962 Jaru.lIry 1972 (Ievi"d Augu.t 1972) u.S. Depa.rt_nt of tbe Int.rior, Geological Survey, Hydroloaic U.S. Depart_ot of the Aray, Corp. of EDain.ers, ~ ~6CliMtol0Rie Data Collected t:hroulh 1964. Salt: Lak. Coumy, Cloudburst. Salt Lake County. yt.h, Internal Report, Deceaber 1916 u.S. Depan.. nt of the Interior, G.olOlicd Survey, Hydrologie U.S. Depart_nt of the Anay, Corp. of Enlin.er., HydroloRic I.IUl Cli.toloRie Dat:a. 1965. Salt: LAke County, 1966 !alineerinR Center, Technical Paper No. 64, Det:'I1Iininl Peak Dilchtrae Freguegcie. io an Urbapiain. Water.hed: A Cal! Study, u.S. Depart_Dt of the Ioterior, Geololical Survey, Technical PaVil, California, 1979 Publication Mo. 31, Vat.r I"oure •• Dat:a of Salt: Lake County, 1911

u.s. Depart_nt of Trtn.portation, p.d.ral Hilhuay Adainittrltioo, BUtololY for Trap'POuat:ioo Inlin.er., 1918

23 24 Utab Wat.r I ••••rch Laboratory, Report No. PRwe 35-1, Hydroloaic U.S. Depart_nt of Tran.port.tion, Pederal Highv.y AU., of Utah, 1968 Adain1.tr.tion, lugoff IUiNt•• fot' SHll Watenhed. and Dlv.lo_pt of a Sound De.iln M'thod, 1977 Vi .....n, W., J.W. ICnapp, C.L. Levi., .nd T.E. H.rbaugh, Int.roduction to Hydr0101Y, Harper .nd Rov, Publi.herl, 1977 U.S. !nviroOlllntal Protection Aiency, 2PA-670-75-046, R.infall lupoff Relatiop. on Urban and Rural Arelt, Cincinnati, Ohio, 1915 We.th.rbtDk, Inc., !.tiyted Return - Period Isopluvitl Maps fot' S.lt 4" 'IIU.y, 1977 U.S. Ceololictl Survey, Surfas, Water Resot'd. of Utah, Separate book. for eacb year, 1961-1964 9.0 IBYISIQR DESCRIPTIQHS U.S. Geo10lical Survey, l2tb Annu.l Report, Part II, Irrilation 1890-1891, 1891 Tbi. '.CtiOD ba. been .dded to provide information r'lardinl .ilnificant revitionl ..d •• ince th. orilinal Plood In.u,..nce Study V.I printed. U.S. Ctololical Suney, Unpubli,h,d StrellDflow Oat •• Peak. Future r.v1.ion. _y be ..d. th.t do not r ••ult in the republilhing of Disch.rle Streaaflov Record. for Miscellaneou. Gaging Statlons the Flood Inlur.nc. Study report. To "'ure that .ny u ••r i ••wat'e of fro. uses, Kainfr... co.-puter file., 1990 .U r.vision., it it advillble to cont.ct tbe cOlllllUnity r,po.itot'y of flood haurd d.ta locat.d at the Salt Lake County Department of Public u.S. Ceololictl Survey, Wat..r Re,ourc" Data for Ut.h, Part 1, Work., Flood Control and Hipvay Divi.ion, 20001 South St.t. Street, Surf.c' Water Record., Separate book. for eaeb ye.r, 1965-1974 _r .3300, Salt Lake Cit,., Utah 84190-4600.

u.S. Ceololieal Survey, Water a ••ourc" D.ta for Utah, Separ.te 9.1 Pir.t I.vition book. for elcb v.ter ye.r, 1975-1980 Thi ••tudy v •• r.vi"d on Septeaber lO, 1994, to include the r •• tudy of tb. Jordan liver conducted for PEMA. by CU2M Hill under U.S. Ceolo,ic.1 Survey, VU,r Ile.ourc" O.ta - Utab, Sepat'ate Contr.ct 10. 1MII-9O-C-3104. The re.tudy va. co.p1.ted in Hovem.ber book. for e.cb v.ter yell', 1981-1989 1992.

U.I. Ceololical Survey, W.t'r-Supply Paper 157 Th. Jordan liv.r v •••tudied in d.et.il fra. the Utah - Salt Lake COunty lin. to th. Surplus Canal cliv.nion n ••r 2100 Soutb Street. U.S. Soii Con ••rvation Service, "tioMl Enlineerina HlDdbook. The Itucly .r.a includ•• portion. of th. unincorpor.ted area. of Sectiop 4. BUro10u, 1972 Salt Lake County, al ...11 •• portion. of the Citie. of Welt V.lley, South Salt Lalte, Murray, Mid.v.le, W•• t Jord.n, South Jord.n, S.ndy, U.S. W.ter le.ource. Council, Hydrology Co_itte" Flood Plov liv.rton, Dr.ptr, Bluffdale, .nd Salt Lak. City. PreqUlpsy for YDI.,ed W.terlhed.: A Lit.r.ture EvalUAtion, 1977 Hyd.rololic analy••• vere performed to e.tabli.h ditch.rl,-ft'equency Utah Dep.rt_nt of ••tur.l I •• ource., technic.l Publication r.l.tion.hip•• t four loc.tion. in the Itudy re.ch of th' Jordan Ho. 21, Sw.aa of Ma"i.. Di.ch.n,. in Ut.h Stre"., G.C. Riv.r. Hittoric .tr.aaflov dat. were analyz.d in accordance vith Whit.ke, 1969 crit.ri. outlin.d in Bull.tin No. 17B, Cuideline. for D'termininl Plood Plow Fr.qu.ncy (Referenc, 19). Utah Ce.olOlic.l A.. od.tion, CloudbyrU .nd SnoWIDIlt Flood •• Ipvit'ORMPttl Geolo,y of the W... tch Pront, 1972 Hittoric Ut.h Lak•• tale r.cord. belinninl in 1884, and a hilh vat.r r.f.renc. of 1862, vere u.ed in conjunction with a Itag' Utah Office of Planoinl and 8udl.t, Utab DeItolraphic R,pot't ditchara' curv, to e.ti.. te bistoric n.tur.l dischar,e. in tbe DIM'Xapbic aAd !sopo-is Analyti., 1991 Jordan liv.r. Th ••• d.t. vel" u.ed to .uppleaent the U.S. Ceololic.l Survey (useS) ttreaaflov data to dev.lop the di scharle Utah Wat.r R•• earch Labor.tory, Re90rt Ho. Plwe 86-1, Application fr.qulDcy curv••• of • BUrolo'ic Hod.l to the Planpinl .nd DelilP of StOni ~ STat_ or yrbtD Ar ••• , 1976 Th ••tr.aaflov "Iinl record. for the Jord.n Rivet' con.itt of tvo data population•• 1 • re.ult of tbe op.rational effects of the Utah W.t.r Re.urch Labor.tot'y, R.port No. UVlL/P-80/01, f.l.2.2!l CoeprOlli •• Aar._nt: natur.l 1'.1'..... nd pumped t'el ••• e. tleeel' "itjc.tiop iq ytAh, 1980 (I.f.ranc. 20). Th. two d.t. 9Opul.tion. vel" anal1.&.d

25 26 independent I, to develop Hood flow frequency curve. for Inowa.elt evea.tl, .1 it v •• det.rained tbat flood. caused by .noVMlt event. ltOdel flov tht'ouab two of the eoncrete cHvereion .tructure. on the are len.raUy -are ••vere than tho.e cau.ed by rainfall events. river. PIOtld peak. eau.ed by rainfall ,venti vere not evaluated with peak. cau.ad by 'DOWIMIlt eventl .0 that the data popuLation. would be Ortbopboto topo,r• ..,hic ..p. with ••c.l. of 1:4,800 and a contour ho.tleneou.. The ",t •• vere .nOWIMlt flood. on the Jordan River int.rval of 4 feet, with 2-foot .uppl.ment.l contour., were are aUGei.ted vitb natuul relea ••• and biah levets of Utah L.ake. provided to th•• tudy contr.ctor by Salt Lake County (Reference 22). The pboto,r.pb date of th•• tudy .rea wa. Hoveaber 11, 1990 . Di.ehar•• contribution. to the Jordan liver fro. Mill Creek Big Cottoov004 Cr•• k, and Little Cottonwood Creek were based on' Pive .hallow floodin, or pondinl zonel (Zone All) .re identified on e.tiuted 100-y•• r tributary ditcta..rgea at the canyon lDOuth. tb... pl. Ooe of tbe.e .re•• i. locat.d ju.t downatre.. of the Big developed by the U.S. 4r8y Corp. of EDlineers

27 28 3 3 3'/ Al,o, a' a part of this update, the Flood Insurance aate Hap for tbe City of Soutb Jordan wa, converted to the Map Initiatives for.at. In the ..p initiatives fo~t, all base flood elevations, cro., section" and floodplain and floodway boundaries are ,hown on the Flood Insurance aate Map. The Flood Insurance Zone Designation. were chanaed to reflect the Hap Initiatives format as follows:

Zone A

Zone A i. the flood insurance rate zone that corresponds to the IOO-year floQdplain. that are deterained in the 1100d In Jrance Study by approaiaate .... thod.. Because detailed hydraulic analyses are not perfo~d for such areas, no baae flood elevations or deptb. are .hown within this zone.

Zone A!

Zone A! is tbe flood insurance rate zone that corruponds to the IOO-year flOodplain. tbat are determined in tbe Flood Insurance Study by detailed ..tbods. Whole-foot base flood elevations derived frota tbe detailed bydraulic analyses are sbown at selected interval. witbin tbi. zone.

Zone AS

Zone AS it tbe flood in.urance rate zone that correspond. to the ar'" of laO-year .ballow flo04ina (u.ually areas of pond ina) vbere averaae deptb. are between I &ad 3 feet. Whole-foot base flood elevation. derived frOil the detailed hydraulic analyse. are .bown at .elected interval. within this zone.

Zone X

Zone X is the flood in.urance rate zone that correspond. to areas oUClide tbe SOO-year floodplain, area, wi thiD tbe SaO-year flood plain, area. of lOO-year flood in, where avera,e depths are 1... tban 1 foot, ar.. , of lOO-year floodina vhere tbe contributina draina,e area i. Ie•• than 1 square .ile, and area. protected fro. the IOG-year flood. by leveel. 110 ba.. flood elevation, or depths are ,hoWD witbin tbil zooe.

In addition, tbe Flood In.urADce Zone Data Table va. removed from the. Flood Inlurance Study report, and all zone designationl and reach determination. ware rellOved, fro. tbe profile •• ~ ~ ~ ..~ ·• L ·•U - • .. C ..~ ~

•> :! § ~ < ~ ~

• ~ • ~ . « ,• -- - ~ i z «c , ~ .0 UGINO « ,l ~~ ~ "I . ~ nooo .5 ' 00 ve .... ~lOOO •0 " - ~ '.C" - so nAR H OOD 0 ~ ~ ------10 VEA .. FlooO • C ! > STlIl _ 1[0 e «" U CIIOSSSICT'OH • '6 lcc.aTION ~

STil i ..... OInANCII"" HIT "'4OV1I MOUTH I DIP M ~ ~ • a - -L -•U > -a a ! a -~ •> i 5 0 .. •~ •> .- ,- - - ~- ~ ~ •, z •~ • ~ c " UGlNO ~~ '1'("''' flOOO J x " .. .~ - '00 Yl ... " HOOD ~ '. !II "'I ... ". ~lOOO ~ ~~ ~ •C • - 10 YI ... ,. ~lOOO - -- ~ > S"'l"-M 110 " •U C!lOSS SECTION • '3 LOCAl ION .... ~ I"fIlIAM OIITA*:I1III nlT ... 1OVe MOUnt - 02P !?/ w~ ~ • , 0 • I -L "> -0 • 0 0 0 , -~ •> 0•

> •0 ~ « ~ ~ , • Z· ! c,« .0 llGINO ~ CO •« YUII HOOO , ,<" .. > ~~ -- ,.. n ", ,, H OOO ~ ~~'. - SO '1'( .0. " H OOO •0 ------.. 'HA" H OOD .-C > 5'"V..... BE D ! ~ «" u cnoss SE CTION • 6 U X:,A TION ~

"IIUM DlSTANCllN nn AIOYI MOUTII OlP I , :: ,":': r;: I,:!!: 1 ,1: :;:::::: I : : iii i i ~ ; , ' ;: ; I , I I id ! , : .. ~ ; , I , I I , :1:: ,": ~ , ~ , , "':!' . .. , :. • I I ~ " i :. ' ;".!. ,I -0 - -•u , L , ! ~. !'. ~ -0 ~ 0 ~ , 0 i ii " i; , ' :.,: ~ , , , - I , ~

• u• :11 ~• •, z ;: : •; < u .,0 - ~ ~ c (Jm I • ~ ~ ~ ., .. "n ooo t ,• z · .~ 'OIl nA,A't OOI' r •u • 0"'. o,n VIA

04P I w I ~ - ." D • - "U .. ~ -D D " D i -~ •> i E• I ~ •< 2 m "" ~ - ~ ,• ~ z • ~ o ~ • •< UGI"D Z " 8 - < ~. ~ VEAR HOOO ," •C S ~ ,.. YUllfI.. OOO z -- g ~ - W YEA" JlOOO ~ - 10 V(A" HOOO •0 • - > STIIE ..... UD ! > <" 0 CIIOSS S(C'''ON ~ -6 lOCATION - -- 2 ITRI AIII OIIT.t.JICt .", ' ''l'''~..avnt , 05P , , , .. . - . • ~ . · 1 _.. . __ . . ... _ . . t .. •' ._.LI L,.. • il , ~ i ! • : 5, ~~ : gl i• ... . 0 ~ , u I~ I -~ .. , , , I -0 ~ I I ! : L ., --_ . .. ,! i - - _. . • . -,. --- -, ._--. ~- - - - - · . -0 0 0 I ~ i ~ 1 - . ~ r , _. . 1_ ____ .--1 __ __ _ .4. __ .-- -_ .. . .,20 I ! . , . , --:- ~ ---4"0 ..... --~- :::.=.:=:------:. -~ __ - t , .. ···-r·· - . .. . .- - , I 1. i , 6 ~ ~ ...... I ---_ . -, _._. -- , .. I

~ . CIlOU Sl Cl U)N l OCATION " .. .. " " " " " " " 06P ...• ..•. -1:- .II - - i--- li..! .. i.- I " I as --~'I' '=-'-,-1 I il -'---!---"+H

~ ., - .... . t-:-. ..• • " ~ 1;'-. -; 1--' ' .. , "; '21'· . ~~:- -',' "l v i: i 'H r' - '"0 .. .. " H_ , ....•. ···· 1·.," .,· I ". I"I H- , .1, L: i -, •. ,',:' : ':.. H 'HH H' . .. H·I ·"'" I -L t -0 0 0 ~ I J k f~1- "·i .i': ·fl·: t-:~-' ··-t~~+··: : - "'" 11 " ;,' ~'.: . . ' t ,." J -i ;---c;-_ ..... ,L. -1 :. · -· rt ·••. 1i • 1 'Ii. · ' 1- ! ~.ao ' - -L-. ___ J . j . - ~> .. : --1 -::- ----1 '-- .· · -: ...- r' - ~ -- ~ : ! 'I , . --~~----F ·· : 1 _~L _ i---- ! - :" :: 1 : '

.. : __ t- i ~: j ~ ' ; _~_i _ _ ~_ . .. 4110 ,.. i : f//' . 1 ~ -j I . ~ 'I ,:,. , ; , I : 5 -I ' , : I · , ii' . zl uoo l~-T ... ';-.-- --"j" ---T---:--i ---·t-- ~ .'~.-- r- - ---~--- ie' ===~u~,,~.,===9iuoo ; Is til ~ I ~ i ~~ Ll l. i ~----~----,q. - ~t ~ I ~: ~ __ J:.._. _ I _ ___ ' 71 10 ., . -- - - n ...... " L-______""lAM DlSTAIoICIINTMO!JaANOI 011 'lIT -..oYI .uIlPWS UNAl DlY'lillIOM ______.-- 07P