Anthropogenic forcings on shallow landslides triggering

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1 Antropognc forcngs on sallow lansls trggrng Mara Crstna Rull, Poltcnco Mlano

2 Factors wc nflunc or trggr mass movmnt lop atr Antropognc an natural actvts

3 0 < z < < z < z < z < <z< z [ ] ( ) φ sn z z c c c Fs v A ( ) [ ] { } φ sn sn z z c c Fs sat w sat v ] ) ( [ ) ( ( ) [ ] { } φ sn sn z z c c Fs sat w sat A ] ) ( [ ) ( ( ) ( ) [ ] { } φ sn sn z z c Fs sat sat w sat w sat ] ) ( [ ) ( φ br Fs ( ) [ ] { } φ φ sn sn c c Fs sat w sat ] [ )), (mn( ), mn( Prcptaton nuc lansls at basn scal T problm s usually solv n trm of F by couplng an yrologcal mol wt a gomcancal mol Rosso R, Rull M.C. Vannucc G., RR 006

4 Roas ffct on sallow lansls trggrng

5 Hyrologcal Effcts: Roas Effcts Roa surfac an Dtcs Incras Ovrlan Flow Roa Cut Intrcpt ubsurfac Flow Culvrts A nw Cannl to stram ntwork Cannl Ntwork Extnson Q( t) Incras quck scarg Q Q quck bas Q Q Q ran quck cutroa t roa tout roa Incras an antcpaton of pak scarg Volumtrc an Tmng Effct Tm (From mpl, t al. 996)

6 Flow Intrcpton by t ROAD Ranfall Effct on t roa Hp: Imprvous Roa urfac mall rougnss Nglgbl vgtaton transpraton an ntrcpton Hyraulc Analogy: Roa - Cannl a. Outslop b. Inslop c. Crown Q ran I r A roa Runoff gnraton on t roa an on t tc a b c

7 Flow Intrcpton by t ROAD Effct of t roa cut Ovrlan an ubsurfac Flow ntrcpton Q Q Q roacut ovrlan subsurfac nt Q subsurfac Ovrlan-roa Q subsurfac subsurfac l nt ( ) ( ) wt wt nt wt wt

8 Flow Intrcpton by t ROAD T ntrcpt scarg by t roa s rout ownslop troug t culvts Dranag pats Cangs Culvrt connct to t actual ranag ntwork Culvrt connct to pmral cannl Culvrt not connct L Rg L Rc Epmral Cannl L C rvr L D A L Dranag Dnsty D ( L L L L ) Rc Rg A C

9 OUTLET Roa Roa T prsnc of ROAD can mofy contrbutng ara at slct pont

Gomcancal Effcts: Roa Influnc Gomtrc Effct Go-mcanc Effct

Loss of vgtaton ovraccar co Loa ovuto u to al fllslop trrno

Cut slop lansls trggrng Fllslop lansls trggrng Dbrs flow

10 Gomcancal Effcts: Roa Influnc Gomtrc Effct Go-mcanc Effct Hyrologc Effct Incras of slop n cutslop an fllslop aras Loss of vgtaton ovraccar co Loa ovuto u to al fllslop trrno rporto Incras of sol watr contnt n ownslop culvrt aras. Cut slop lansls trggrng Fllslop lansls trggrng Dbrs flow Incras of sallow lansls Dbrs flow ar not takn n account n t prsnt analyss

11 allow lansls typology Hllslop ls (nfnt slop analyss) Cutslop ls (tablty maps) Fllslop ls (tablty maps)

12 Hllslop LIDE Infnt lop Analyss ca cv c Fs [ z ] ( z ) sn φ 0 < z < {[ ( z ) ( )] } c cv sat w φ Fs [ ( z ) ] sn sn mn( c, c) Fs ca c Fs [ sat {[ ( ) ( z ) ] } {[ ( )] } [ sat sat sat sat w w (mn( φ, φ)) ] sn sn ( z ) ] sn sn φ < z < z < z < c Fs {[ ( ) ( z ) ( )] } [ sat w sat ( z ) sat sat w ] sn sn φ <z< φ Fs br z Fs most probabl slng surfacs Profontà z rsptto al pano campagna (m)

13 Cutslop an Fllslop LIDE: tablty Carts analyss Hypotss: Crcular falur surfac llslop smpl gomtry ol avng frcton an on ol omognous an sotropc Frcton crcl mto Mor-Coulomb: afty Factor: wt λc φ P tgφ c H q H ' P µ µ ' q τ c σ φ F N P an P CF c H q H µ µ µ q N c H t Taylor, 948

BAIN PARTITIONING: stat of t art T mol s a contour-bas mol.

procs ownslops follow t stpst lns (Mnun t al., 000).

routng: Cll : polygon avng two vrtxs on two ajacnt contours an

Cannl: mono-mnsonal topograpc lmnt startng at t juncton of

14 BAIN PARTITIONING: stat of t art T mol s a contour-bas mol. It rvs at frst t ranag ntwork startng from t gst contour, tn procs ownslops follow t stpst lns (Mnun t al., 000). Two typ of topograpc lmnts ar consr n flow accountng an routng: Cll : polygon avng two vrtxs on two ajacnt contours an two vrtxs on two stpst lns. It can b trangular wn stpst lns mt. Cannl: mono-mnsonal topograpc lmnt startng at t juncton of stpst lns T ffct of prsnc of ROAD on basn parttonng OUTLET Rull M.C., Rosso R., 008

Hyrologcal Fluxs mplf Buckt Mol wt Layrs L L Z

Unsaturat T aturat BIN Rock IE t OF t EX t F t

, AR 007 RF t E t E t aturat aturat BIN Rock OF

K 0 ov f m atr Contnt: ( z s z ) ( θ θry ) ( θ

ubsurfac Flow: sf Infltraton: ln K m ( ) K I s

15 Hyrologcal Fluxs mplf Buckt Mol wt Layrs L L Z Z s Z Z s RF t IN t Unsaturat T aturat LIN Unsaturat T aturat BIN Rock IE t OF t EX t F t IE t EX t F t Rull M.C., Rosso R., AR 007 RF t E t E t aturat aturat BIN Rock OF t F t F t aturat Hyraulc Conuctvty: θ fz θ ry K K 0 ov f m atr Contnt: ( z s z ) ( θ θry ) ( θ ) z θ ry Flux unsaturat -saturat: I st K ubsurfac Flow: sf Infltraton: ln K m ( ) K I s ( θ ry ) z I Prcolaton n t crack Rock: bn K t con ar K ar K f K b I I θ I I m

TUDY AREA tuy ara s watrs 3 (3) at t H. J. Anrws Exprmntal Forst, Orgon. Locaton of roas, culvrts, an nstrumntaton ar sown. Elvaton 470 050 m a.s.l. Ara km Clay ol Macropors n t sol Ks 0-3 0-5 m/s Man Annual Prcp.

16 TUDY AREA tuy ara s watrs 3 (3) at t H. J. Anrws Exprmntal Forst, Orgon. Locaton of roas, culvrts, an nstrumntaton ar sown. Elvaton m a.s.l. Ara km Clay ol Macropors n t sol Ks m/s Man Annual Prcp. 300 mm Man ranfall Intnsty 4 mm/ Man Dscarg 5*0 - m 3 /s In orrs of roas wr bult. Ranfall vnt 3-9 Fbruary 996: max ran mm/ Total ran 340mm 6 sallow lansls: 8 llslop 8 fllslop/cutslop Rull M.C., Rosso R., 008

17 Goo Mol rproucton Upslop roa: lansls trggrng s manly u to t gomtrc ffct. Downslop roa: lansls trggrng s manly u to t yrologc ffct.

18 cnaro : ncras of t numbr of culvrts Obsrv sls: T ncras of t numbr of culvrts cras t sls bcaus cras t contrbutng ara at any sngl culvrt

19 cnaro : ncras of t numbr of roas By ncrasng t numbr of roas ramatcally ncras t numbr of sls.

20 Rull M.C.,Boccola D., Rosso R., JoH 006 FIRE INDUCED HALLO LANDLIDE TRIGGERING Fr Forcng on Hyrologcal Procsss Vgtaton covr structon & canopy covr & roots at 0-0 cm of pt Incras ovrlan flow, smnt yl an sallow lansls suscptblty Formaton of a watr rpllnt layr? formaton mcansm? tcknss poston uraton sol typ tmpratur vgtaton covr watr contnt Effcts on sol proprts k ncras n roblty k cras n nfltraton capacty k cras of on

THE EVENT OF 8 t OF JULY, 005 T tuy Ara.

Gology: grantc gnss; n t gst ara, larg zons wt xpos grantc

mm) Vgtaton: Cstnut Hyrograpy: pmral strams Topografy: stp slops,

000 to t ay of t forst fr, 47 ranfall vnts occurr avng or ntnsty

It mans tat t rol of forst fr n trggrng mass movmnt soul b takn n

21 THE EVENT OF 8 t OF JULY, 005 T tuy Ara.6 km catcmnt (Ro Caslla) locat n t Pmont, Italy Major Faturs Gology: grantc gnss; n t gst ara, larg zons wt xpos grantc formatons Clmat: mtrranan Ran: manly n May an Octobr (MAP s 300 mm) Vgtaton: Cstnut Hyrograpy: pmral strams Topografy: stp slops, lvaton rang a.s.l. Rull M.C., Rosso R., GRL 006 vr ranfall vnt. About 40 mm of ranfall ropp n lss 30 mnuts (TR 0 yars ) on a prvously burn sol. Mass Movmnt Trggrng (30000 m 3 ) In t pro from t bgnnng of t yar 000 to t ay of t forst fr, 47 ranfall vnts occurr avng or ntnsty or total gratr t ranfall vnt trggrng t mass movmnt of July 005. It mans tat t rol of forst fr n trggrng mass movmnt soul b takn n consraton. Ranfall [mm] Tm [mnuts] On 6 t Marc 005 a svr forst fr occurr n t ara of Ro Caslla burn mor 70% of t stuy ara. 8/07/005 brs-flow 9-0/09/ /09/ /0/ //00

22 To nvstgat t nflunc of cangs n lan covr an sol caractrstcs, from pr- to post-fr contons, on runoff proucton an sallow lansls trggrng, urng a ranstorm Fl Data Vgtaton urvay (Pr; Post an Transnt) ol pt masurmts DPT tst ol typ Pology Gology Hstorcal Ranfall Rcors Hyraulc conuctvty masurmnts (Pr; Post an Transnt) Molng an prctng yrologcal an smntologcal rspons of burn aras Dtrmnstc mol mulaton Runs POT - FIRE To prov a trmnstc framwork for stuyng sallow lansls suscptblty n t ffrnt tmporal scnaros POT- FIRE/ 6 MONTH PRE- FIRE Frcton Angl [ ] aturat ol pc. gt [KN/m³] Coson [KPa] Apparnt Coson [Kpa] BM Paramtrs POT-FIRE TRANIENT/ 6 MONTH aftr t forst fr PRE-FIRE ol pt upslop [m].5.5 ol pt ownslop [m].5 3 Ks upslop [m/s] Ks ownslop [m/s] / / / / / / Multplng factor for orzontal K s [-] Rat of cay n K s wt pt [-] atur sol watr contnt θ [- ] Rsual sol watr contnt θ N [-] Intal satur stor of t buckt [%] Intal sol watr contnt - upslop [-] Intal sol watr contnt - ownslop [-] POT-FIRE TRANIENT/ 6 MONTH PRE-FIRE Mannng coffcnt - lops [s m -/3 ] 0.04/ / /0.04 Mannng coffcnt - Cannls - upslop [s m -/3 ] Mannng coffcnt - Cannl ownslop[ s m -/3 ] Crtcal upport Ara [-] Cannl t calng Factor [- ] Outlt Flow t [m] Tm tp for t Knmatc av [s]

23 Tmporal cnaros - pr-fr: t pro of tm bfor t forst fr occurr - post-fr: t pro from t tm wn t fr stngus to t n of t sprng n t subsqunt yar - transnt: t pro of tm rqur for t rstoraton of t sol, followng fr nuc sturbanc TRANIENT POT FIRE POT FIRE PRE FIRE Rull M.C., Rosso R., AR 007

24 Conclusons: Antropognc an natural actvts lk roas an forst frs can strongly nflunc t yrologc rspons an sallow lansls suscptblty of uplan catcmnts! For stuyng antropognc an natural actvts nflunc on sallow lansls trggrng t s ncssary corrctly valuat t ffcts of ts actvts on t yrologcal fluxs (gnraton an rcton). For stuyng antropognc an natural actvts nflunc on sallow lansls trggrng t s ncssary corrctly slct t gomcancal mol! THANK YOU!

25 ( ) [ ] ( ) [ ] θ φ ω ω ' r r s r r s G G F > ; * ln f, ; * ln f, xp * p p A p p A A p p ξ ξ ξ ω a Tb p snθ * ( ) r A ω /z ξ (p*/z)t

26 Prcptaton trsol for slop nstablty Couplng llslop yrology wt gomcancs yls lansl trggrng by prcptaton ( ) ( ) t az Tb t az Tb z G a b T t p r r r r s CR θ θ φ θ φ θ θ sn xp sn xp ' ' ) ( sn Tmporal scal of llslop voluton T ranfall rat p F tat can b xc wt a probablty of ( F) n a yar ( ) ) ( n F F t x m t p p CR p CR (t) ( ) ) ( sn xp sn xp ' ' ) ( sn n F r r r r s t m x t az Tb t az Tb z G a b T θ θ φ θ φ θ θ

0 t [] 00 Maps of Mttman Rg catcmnt sowng sallow lanslng pron aras n trm of

27 p CR an pf [mm/] a/b 00 m a/b 50 m a/b 00 m 00 a/b 00 m TR 500 ya TR 70 yars TR 5 yars t [] 00 Maps of Mttman Rg catcmnt sowng sallow lanslng pron aras n trm of rturn pro of potntal falur consrng ntal conton of stabl pzomtrc at t pt of brock, (0) 0 an (0) 0.5, φ 45, T 65 m/, ρs 600 kg/m3 an Gs.60.

Guo, James C.Y. (1998). "Overland Flow on a Pervious Surface," IWRA International J. of Water, Vol 23, No 2, June.

Guo, James C.Y. (1998). Overland Flow on a Pervious Surface, IWRA International J. of Water, Vol 23, No 2, June. Guo, Jams C.Y. (006). Knmatc Wav Unt Hyrograph for Storm Watr Prctons, Vol 3, No. 4, ASCE J. of Irrgaton an Dranag Engnrng, July/August. Guo, Jams C.Y. (998). "Ovrlan Flow on a Prvous Surfac," IWRA Intrnatonal