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<br />~lar'ch 23" 1':190 Draft Report "- FOR REVIEI-J ONLY <br /> <br />mtlt.lflo\.r',lS (~::tlckelman!1 1986)" l'1Bppjng of an;:as sur.,;c.eptibJE.' to J8ndEIJdC's, <br />including mlldflD~'JS~ is:. essential to t.heir mitigation (I;Jold and Jochim, 1989) ~ <br /> <br />AJthot.lgh lcmdsJide pDt~ntj.~d e~d.sts in ENe~ry state!! thf.~ Jj'tf..?f13'h.lle dDc,s- not <br />di-fferi?'flt.irJ.t:e the typE.~S of landslides gec)graphically~ The l:i t.ei"aLure <br />:!.n(1iCi..~tE'~-, in fact that most types of land~:,lidt:~s are mapped and mane:ged 85 one <br />hazard. In s:mme cor5e=., t;"! single t")"pe may he identified for a spe\::i f'1c purpose <br />(~.uch as f"ock 51 ide ,';\r'eas related tD high~\lay cC1nst.ructic)n and ma.l ntf::'llance) ~f or <br />land:::dide areas may be mapped in relatiDn tel a seismic: h?:z.a,-dR In ge::neT'2rl ~ <br />l.;:.tr3.tC\5 and communities t,.~hich ar!-:.~ mapping and managin9 land1:,,1.ldE.' hiB7:8rcls do not <br />diffei"entiate mudflow hazards from other landslide hazards" <br /> <br />MappinQ Standards: <br /> <br />FIA h;:;\';5 deterrnined that Il.w.. thE.l hazar'd identificatiDn and mitig-.::l:"tioi1 a5p2ct~., <br />[If t.he [ml.tdflov~] haz2H'd [arf:~] unadmird straJ:d.E'!1 from the NFIP standpoi nt "".. II <br />f"l::.D!I llBecausc of t.he limited incidence (If covered mLldflDW:::., to e::-:perKI federal <br />dol Jr.:l\'= m~pping thE hazard nr feder-aJ. effDl.-t mitigi:itil':'Jq thE~ risk dC(12s not <br />appE.ar to l'H? co=.t-~effect.ive or sI2nr::.'ibJ.e at this time. H II FEt"IA shDuld avoid <br />e:ny Federal incur5:.1oD intn matter's OE:st left t:o the t;tat.f:.:'s~ jn a s:,pjrl.t of net,'J <br />federi5'lis.m, leaving the States ~Ij:ith the rE'spDn~.ibility t:t:. doline.ate and <br />Initigate the hazard if it is in the best interest Df the States to do eol! CFIA, <br />198~3) . <br /> <br />At. the ~.;.alTfe timC', howElver, as 8. result of disastTouS ml...\dflol>'Y5 in U\';21tf in 1983~ <br />FEllA ent{?n~d into an i ntergov€'i"THfff!nta 3. agTeement wi th the Corp!';; of Eng:i nee'! e. to <br />provide flDod insurancE' studies \ldth mudflDw hazEI)-ds on l~j stf"e~.m5 in D::phs <br />COI.\\lty, UT~ The COf"/.Jsl Hydrologic EngineE.~rin9 Center' (HEe), in cooper'Htion <br />with thl? University of Ut:ah~ developed a one-dimensional uns:.teady'-flcl~": model te! <br />Si(Jil.IJat:~~ fOudflctwS in alluvial ch~nnels, and a 'tv",o--dimE:i15:iCinaJ IJn5teeldy'~'fJovJ <br />model to simul2:lte mudfltH'.~s on alluvial farls (Lit)u, 1989). <br /> <br />U!..~ing data from the 198a ff;udflclt'Js (jnd othel- histcq-ic data;l the dry volume of i:' <br />lOO--year mudfl{)w lo\!as developed E:lS a function Df Dr~inage i:n-'ea~ Thip.. ./cdumc; was <br />thf.'fl increcIscd by a bulkinq 'fac:tcn~ of l..b to account fcn- the volur(~l::- tif 1.121tE.r 111 <br />t.he fJm':!, Using informat.ion from clbser'verJ mudflo~'Js~ <3 cle.mbreak hydrograph was <br />H~Cr.l 'cO c'stimate t:hf~ hytir012!ri'ph for a mudflot-\l for the Dm:::'-djmerlsioIlEtl mc!oed... <br />This:. hydf"ogr'aph was used with topDgraphic ei;:)ta and fIludflo~1;! fluid pr[\pert:'les for <br />the two"'dimensional model" Aft.er calibration:l these models Wef'E i~ppl ied t.o the <br />all 15 canVDns in Davis County (LiCtu, 1989). They h\ave no~ yet been used to <br />pi"odt\ce Flood InsLn~ancF.) Rate Maps (FIRt'ls) ~ <br /> <br />HQ:st~EH'Ch for t.h:i.e:, 1~epcq-t indica'tes that this is:, the only feder2.'1:!, 5~B,h2 or <br />JI)C~d. effort to dF:d,J.nE!8tE-: mudflol4 hazard areas in accorda.ncE vdth F'Ir:':)ls <br />definition of covered ffludflClwsu In 1;;Ieneral, it '::T,E'effiS that. if CRS cn?di t: i.s:, 'to <br />bF~ g:i.ven for mappinq ~\l"lcl managing this hi:'1ZBi-d, the:..: crpdit ffiLlEt be 2xtendE'd to <br />all JnE:1pped li:rndslide hazi:I}"ds, a~~, i~~ rc~cc.lmHH:mded belo\<',I~ FIA may rejer::t: lhi:;:, <br />r'Gcommenclatir.'(j i.n order to avo:id pntential l:onfusion in the.: futurE' bE'tl'\lpen <br />coveri:.\d mudflOl,o,lS', and landslides, which are 'not Cl)VEred undeT thf;:;O NFIP~ <br /> <br />j"1F--:J <br />