Defining Areas with Nil Landslide Hazard is a step toward a Comprehensive Landslide Loss Model

Transcription

1 is step towrd Comprehensive Lndslide Loss Model F.ASCE, F.GSA, Ame Foster Wheeler, Los Angeles, CA, USA, Consulting Insurne Atury, Huntington Beh, CA, USA, Astrt Lndslide risk urrently is unquntifile in terms suitle for insurers to use for setting poliy pries. Insurers need proilisti models of lndslide hzrds tht quntify dmge likelihood nd extent. Proilisti seismi hzrd nd loss models permit erthquke risk to e identified quikly for ny street ddress. Erly seismi hzrd mps hd four zones sed on inidene of dmge. Ares without topogrphy, geology, or geomorphology onduive to slope movements nd with histories of no slope movement would e Zone 0 (p<<0.01). Ares with slope movement inidene would e Zone 3 (p>>0.01). Zone 1 (p<0.01) would e hilly res where no lndslides hve ourred nd none re expeted sed on nlysis. Zone 2 (p 0.01) would e hilly res where lndslides hve not ourred ut re onsidered suseptile sed on geology or geomorphology. Geo-professionls tend to mirozone slopes in Zone 3, ut insurers would e helped more y well-defined Zone 0 whih might llow lndslide dmge to e inluded in ll-peril poliies. One vile produts re ville, privte insurers will seek to improve risk models for expnding Zone 0 oundries nd quntifying risk in other zones. Lol governments effetively eome insurers y providing reovery nd reonstrution funds following lndslide events. Lol governments nd privte insurers need the sme type of geosiene for mnging lndslide risk. The suess of erthquke insurne suggests tht improvements will e mde in simple lndslide loss models one privte insurers hve vile lndslide insurne produts. Lndslides nd Seismi Hzrds The lndslide hzrd mp denotes res where lndslides hve ourred in the pst (inidene) or where slope nd geology onditions suggest tht lndslides ould our (suseptiility) without regrd to how muh movement might our in the future or how likely suh movement might e. The erthquke hzrd mp displys the distriution of expeted horizontl erthquke elertions (hzrd intensity) orresponding to 10% proility of exeedne in 50 yers (hzrd frequeny), whih is ground motion with n verge return period of 475 yers or n nnul frequeny of Two Big Points 1. To e effetive, lndslide hzrd mp of the United Sttes needs to over 100% of the re. This mens tht it will not e lndslide hzrd mp, it will e slope hzrd mp. However, for effetive ommunition, it should e lled lndslide hzrd mp. Permnent ground displement used y sinkholes proly should e inluded. 2. To e useful eyond zoning, the lndslide hzrd mp must express hzrd intensity orresponding to hzrd frequeny. Lndslide intensity needs to e defined; it would e hrteristi tht uses dmge. Lndslide return period would e linked to proesses tht trigger slope movements (minly preipittion nd erthquke shking). Movement triggered y exvtion or lnd use would e legl issue.

2 Why would Nil Hzrd e Helpful? Privte insurers might offer poliies or even inlude lndslide dmge overge in ll-peril poliies in res where the likelihood of lims is essentilly nil. One lndslide dmge insurne is produing revenue, the logil next step is to develop loss models to enle writing poliies in Zone 1, nd then in Zone 2. By working from nil hzrd (Zone 0), poliy revenues foster reserh to refine models whih requires etter knowledge of lndslide mehnis nd dmge proesses. One loss models hve een developed, susequent investigtions of lndslide dmge will improve understnding of slope proesses nd uilding responses, whih in turn will result in improvements to hzrd nd loss models. Continuing to fous on high hzrd res will not e helpful to insurne ompnies. Erly Erthquke Dmge Mp Lndslides re Not Erthqukes 1. Lndslides re seondry events triggered y primry event 2. Lndslides re not neessrily reurring events 3. Lndslides my or my not tully our given triggering rinstorm or erthquke event 4. Future lndslide movement my e enhned or suppressed y previous movement 5. Lndslides re likely to e influened y limte hnge 1. Erthqukes re primry events 2. Erthquke re reurring events 3. Erthqukes lwys generte ground motion 4. Future erthquke shking is independent of pst erthqukes 5. Erthqukes re not influened y limte hnge Lndslides re more hllenging thn erthqukes Lndslides hve omplexities tht most geologists nd engineers hve long reognized. Suh omplexities result in three importnt onditions for lndslide hzrd nd risk mngement: 1. They mke hllenging single, omprehensive slope-movement hzrd nd risk sheme; 2. They promote omplited onepts nd terminology tht inhiit ommunition of geologi nd engineering ftors with non-tehnil people; nd 3. They ttrt geologists nd engineers to devote inresing levels of effort in explining detils of slope movement proesses so tht professionl soiety onferenes typilly do not involve people with rod rnges of edution nd experiene. Zones of (Future) Erly Lndslide Dmge Mp Slide Zone 0. Slope movement proility is muh less thn 1-in-100 (p << 0.01). Ares with histories of no slope movements nd without topogrphy, geology, or geomorphology onduive to slope movements. Slide Zone 3. Slope movement proility is greter thn 1-in-100 (p > 0.01). Ares with histories of slope movements. Slide Zone 1. Slope movement proility is less thn 1-in-100 (p < 0.01). Ares with histories of no slope movements ut with hilly topogrphy, lthough slope movements re not expeted. Slide Zone 2. Slope movement proility is out 1-in-100 (p 0.01). Hilly res with no slope movements ut with slope movement suseptiility sed on geology nd geomorphology.

3 Jonthn W. Godt, Jeffrey A. Coe, Rex L. Bum, Lynn M. Highlnd,, & Rihrd J. Roth Jr Prototype lndslide hzrd mp of the onterminous United Sttes Empiril pproh sed on topogrphy Lndslide lotions Slope Lotion Numer of slides Period Soure NJ New Jersey th entury present (New Jersey Geologil nd Wter Survey, 2010) SF Sn Frniso By region (Godt nd others, 1999) OR Oregon 10,000 + Previous 160 yers (Burns nd others, 2011) NM New Mexio 3410 Holoene (Br nd others, 1999) NC North Crolin 2824 Previous 70 yers (North Crolin Geologil Survey, 2008) Lol relief Prototype lndslide hzrd mp US ZIP Codes Simplest Quntittive Lndslide Hzrd Mp The region of negligile lndslide hzrd lso defined ZIP Codes where lndslide hzrd is negligile Expliit desription must e deterministi Chllenge t ntionl sle Bsed entirely on topogrphy No geology, groundwter, wethering, glil history, limte, or other ftors Neglets the frequeny of lndslide triggers (rinfll or erthqukes) Improvements Higher-resolution topogrphy? Additionl lndslide inventories in low-relief settings (e.g. Gret Lkes region) Cn the method e used to define non-zero hzrd? Mrhesini et l., 2014, Non-suseptile lndslide res in Itly: Nturl Hzrds nd Erth System Sienes, v. 14 Little effort hs een mde to propose nd test methods to ssess where lndslides re not expeted to our. This is surprising, euse plnners nd deision mkers re eqully or more interested in where lndslides re not foreseen, or nnot our in n re, thn in knowing where suseptiility is high or very high.

4 Defining Ares with Nil Lndslide Hzrd Lotion of Exmple Are Seismi Hzrd Mp Seismi Zones 1, 2, nd 3 re from the erly Erthquke Dmge Mp; Colored nds with numers re from the modern seismi hzrd mp of the US Preipittion nd Geology Mp Dshed lines re ontours of preipittion; Colored re represent edrok geology formtions Lndslide Inidene/Suseptiility Mp Gry re is low lndslide inidene nd low lndslide suseptiility; Colored res represent moderte or high lndslide inidene or lndslide suseptiility Slide Zone Mp for Privte Insurne Slide Zone 0 (light green) hs seismi shking less thn 15% g nd preipittion less thn 400 mm with simple geology nd low lndslide inidene/suseptiility; Slide Zone 3 (ple red) hs seismi shking greter thn 15% g nd preipittion greter thn 400 mm with omplited geology nd moderte or high lndslide inidene/suseptiility; Slide Zones 1 nd 2 (gry) re intermedite

5 Stility Clssifition of Slopes nd Lndslides Clss Unstle slopes (I) Slopes with intive lndslides (II) Potentilly unstle slopes (III) Apprently stle lndslides (IV) Apprently stle slopes (V) Sulss d Desription Ative lndslides; slopes re urrently moving nd lndslide fetures re fresh nd well defined Retivted lndslides; slopes re urrently moving, representing renewed tivity; some lndslide fetures re fresh nd well defined; others pper older Suspended lndslides; slopes with evidene of lndslide tivity within the pst yer; lndslide fetures re fresh nd well defined Dominnt-histori lndslides: slopes with evidene of previous lndslide tivity tht hve undergone most reent movement within preeding pproximtely 100 yers (pproximtely histori time) Dormnt-young lndslides; slopes with evidene of previous lndslide tivity tht hve undergone most reent movement during n estimted period of yers BP (lte Holoene) Dormnt-mture lndslides; slopes with evidene of previous lndslide tivity tht hve undergone most reent movement during n estimted period of ,000 yers BP (erly Holoene) Dormnt-old lndslides: slopes with evidene of previous lndslide tivity tht hve undergone most reent movement during n estimted period of more thn 10,000 yers BP (lte Pleistoene) Slopes tht show no evidene of previous lndslide tivity, ut tht re onsidered likely to develop lndslides in the future: lndslide potentil is indited y quntittive nlysis or omprison with other slopes on whih lndslides hve ourred Stilized lndslides; slopes with evidene of previous lndslide tivity ut tht hve een modified y rtifiil mens to stle stte Andoned lndslides: slopes with evidene of previous lndslide tivity ut tht re stle euse externl fores using movement re no longer tive Relit lndslides; slopes with evidene of previous lndslide tivity tht lerly ourred under geomorphi or limti onditions not urrently present Stle slopes; slopes tht show no evidene of previous lndslide tivity nd tht y quntittive nlysis or omprison with other slopes re onsidered stle Keton, J.R. nd Rinne, R., 2002, Engineering-geology mpping of slopes nd lndslides, in P.T. Borowski (ed.), Geoenvironmentl Mpping, Blkem, Lisse, The Netherlnds, p Keton, J.R., nd Boudr, L.H., 2014, Development of Sinkhole Hzrd for Pipeline Risk Assessment in Northern Florid, in Proeedings of the 10th Interntionl Pipeline Conferene, Sept 29-Ot 3, 2014, Clgry, Alert, IPC , 6 p. Quntittive Sinkhole Hzrd Cumultive numer of sinkholes per yer within 10 miles (in width ins) (divide y 47 yr) Normlized to 1 squre mile (divide y 4700 mi 2 ) Florid sinkhole dtse 1965 to present. Mp of reported sinkholes plotted y width over 47 yer period for pipeline projet Cumultive numer of sinkholes per yer within 0.5 mi long 944 miles of rods (in ins) Normlized to 1 linel mile (divide y 944 mi) Normlized to 230 mi