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<br />~larch 201" 1.<190 Dn,.ft Repor'J.: -- FOR REVIEW ONLY
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<br />J. 2rnd~-:i] 1. dE 'pronE an:,:1as of the conter mi ncus Uni ted Stat.es hE!.ve Di:':'€'ll m[~pp'E'd b'}.! t:hE\
<br />U.S~ Gf.:!ologi.cal Survey (USGS), f]lt a :.cale of 1:7~~}OO,OO(i, \"Jhich :is only
<br />sui t.:able fr.q- the mOL::.t qIPni:~r.al us:?, nnt planninq or reguled.:jon (Ha-dbr-uch Ha].1
<br />et. aI., 19B2). Nap scales (if 1 :250~OOO m- 1 :500,000 Sil-e recDmmendE'd fc))'~
<br />region.:\J. planning. L.ocal land \JSE~ planning requires a mc~p !:E.c:ale of 1::2'+,000 or
<br />IBfgr:?r, ~~.lhile individual pr{)jects require a map sCk"'ile of 1~2~OOO to 1:5~IOOO~
<br />State land!f..li.de mapping for sE?J.c~c:tcd high cisk f;reas has. tH.::.en carrjed out in
<br />C.:d i fCtrnja~ Idaho, N(~w YDrk, P~,:,nnsylvania, Vil-ginia L~i.!$hington (NaLlo'n:al
<br />HE\!EeiH'/:'h Counc:i.l, 1985), Colorado'l Nevada O({')ckelman!f j986) i3nd Utah
<br />(Christenson, 1986).
<br />
<br />The 1:001s .gvai.lable for land!::!.lide m~ppir~g include: geologic:, topographi.c, ~:.[d15
<br />EI.nd gLN':lmOl"phic maps;; 8E\r:i,al photogrt*phy and other ima~leT"Y; CU::CIUStjC :imB~1ery and
<br />profiles::.; ;.:leria} rf:.lCDnnaissanct?; drilling geoph-y'sical studie!5~ computt-?\-ized
<br />ter)"s.in ancdysis; and instr'umE~rrt,:,tion on areas to d~tect movement~ The types
<br />of llk1pS ~.,~hich a)-e mClst useful to planners an?: landslicle inYent!)ries~ lo'Jhich
<br />Eho\lJ t.he lor:.ations, and types of ear"lif-:r. landslide!?_; land!:~licle e,ust"E'pt..ibiJity
<br />mars, which use the various tools to identify areas of potential landslides;
<br />ar;c1 landslide hazi3nj miaps, {i-Jhich Sh<:M the areal p.xt.t?nt tif thf:; J.andsl.jde thrt-~at,
<br />including past lanclslicles and the' probc.ibility of landslides in the future (~\bld
<br />and Jochim" 1989)"
<br />
<br />!dE.y..:,l.",g:...hQ,!.:HJ.!;.:Y..L..""",.JlI has::, df2veloped B. four--compcment process for' pred:ic t '~l n9 debr- i s
<br />flo"'Js~ It separat{-?5 the trig9E~ring evemt from the channEl e\:'eni~ in ordEH' t.o
<br />imrwove the ~iJ-Clbal:'.Iility analy::dsa There are n6 specific threshcllds given~
<br />~:.jllCE:\ they mqst: be de-termin{-;~d on a sit.f.~ .by-.site basisn ThE' four cl):mponE~nt.s nf
<br />t.hei i' mE'chod are hi -s:",tor ieal data, cun-ent CharmfI'l cond it ion:::." ~'.\3 G9.r.shed
<br />condjtic,-)")s f.Ind calculation tlf the mai-d.mnm event (L.hlJ.:i.Bffis e'L, c:tl'~:r j989).,
<br />
<br />A landslide irrv'2ntor}' map ~Ji3S prepared f(l{- about: fi.ve sq\..\are miles of the
<br />CI)i3St.21J Santa Cl-UZ rk'untains Dt-"Jar 6:.i~.L...._..,tjf~!.mi:~.A at a scale of .1'.;Zt,800 U':::J.iilg
<br />l3ef".jBl phcd:.ngj-c:lphs datE'!d from 193.1. t:hrm.\gh 1982 aIcing with fjeJd inV8s,tjgai;j.on..
<br />Thesr.:~ WElPS i.n-e int.ended to identify UmD~,t and least: hazardous areai:E_ll tD
<br />dt:ter-lllin<:~ the i1f.~(2d for. addit:ional gf::-ologic data prior t.o deveJopmcnt
<br />nHec.f:o'rek ~ 1981..~) ~
<br />
<br />~tt~~.h__."__~f;:_~UJ.t~..!L..,...,_ljT has worked \.'Ji'th thE.\ U~S. Beolclgica.l Survey l~() pl"OdllCe
<br />~Jr::mE'rl'31j2'ed debris floi.v and slope maps:; at a scale of 1;:2'~.~JH)O~ uTher::e maps
<br />differentiate debris flow ella-lined:, and alluvial fans UPC)}"1 ~~Jhich d@PDs'j!.:ion is
<br />ar:tjvf:?lyoccurring fi-om debris fJcr)\lS,,~<. In addition, all mOl.lntc:dnou!:. t~rE.as
<br />with slopes greatej- than 30 pf:?r c:e-{)t are cnnsidered to be susc:eptH:de t:o debris
<br />fJowsH" The acc:c1mpi;my:i.ng te;d; n:;!c:ommend~:i that a d:=.,tai led gecdog:ic hi.l:':"~~f"ds
<br />invE<stigation be perfDI-med in all geDlogic hazard ar"ea~ on the maps "For
<br />st,-uc:tun=\f::. designed for human habitaticl"O and cE.\rtain cr.it:ir.:al si~rl.1(:t:l,ln;:cs
<br />(Robison, 1989).
<br />
<br />Becommendations for MappinQ Credit:
<br />
<br />MF--4
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