VOLCANIC LAHAR HAZARD DESCRIPTION VULNERABILITY A lahar is a debris fl ow that originates from the slopes of a volcano Because Mt. Rainier has been quiet for the past 1,000 years with no indica on of change, this hazard has a low and can surge tens or even hundreds of miles downstream. A probability of occurrence. Nearly 900 proper es could be damaged or destroyed by a Case 1 Lahar. The combina on of Lahar is one of Mount Rainier’s most destruc ve hazards. Historic these impacts suggests that the region is highly vulnerable. Because a Case 1 Lahar has a low probability of occurence, evidence reveals Rainier Lahars buried large swaths of lowlands as the overall Case 1 lahar is assigned a moderate risk. far as the Puget Sound. Lahars can occur without a large volcanic erup on. Probability of Occurrence Vulnerability Risk Low High Moderate Lahars are commonly ini ated by: • Large landslides of water-saturated debris DelineaƟ on of Lahar Hazard Area • Heavy rainfall eroding volcanic deposits A Case 1 lahar origina ng from Mount Rainier is considered by scien sts to be the most appropriate scenario for • Sudden mel ng of snow and ice near a volcanic vent by hazard mi ga on planning. Case 1 lahars could be high in C A I N S L E E S T AR CA D IA Q McNEIL IS U LAND STE AMB OAT HO P E A HARTSTENE ISLA ND X B ISLA ND ALCH I N PA I SS S A ISLAND TAYL O R GE L BAY A JOHNSO N N POINT E consequence and pose a major hazard to human life and D HU N TER G radiant heat or on the fl anks of a volcano by pyroclas c fl ows POIN T A S ITAS MI S UN SA L POIN T A P T T BAIRD E COV E N BR IS CO E L DE VILS N POIN T O I L HE AD DE ER T ANDERSON N BIG Y HA RB O R E N FIS HTRA P I A TT AMS TERDA M ED GEWATE R R Thurston County O LI T T L E BAY D D T BEA C H FIS HTR A P N WI L DC AT N CO V E A O L S GALLAGHER I CO V E S TR EB LE ISLAND N SANDERSON O T R POINT E DO V ER ZANGLE R L HA RB O R CO V E T N POIN T E I E M K U K O BOST ON D O K HA RB O R property in the Nisqually River valley should the Alder and N S DO FF L EMY ER EAST E L POIN T T E ORA T LI BAY H CH AP MA N SILVE R • Breakout of water from glaciers, crater lakes, or from lakes dammed by volcanic erup ons BAY ORA BAY SPI T WOODARD BAY ELIZA N BEA C H DOG FISH BIGH T SANDY T POINT E NE H BIG T NL SLOUGH N C STER Y I E Y A BUTTERBALL I A L S Case 1 Lahar Inundation Zone BU RN S P OIN T B O FRYE COVE Q E N U R CO V E A I DEWO LF LLY CO U N TR YS ID E GULL BIGH T BU RN S BEA C H CO V E HA RB O R MA L LA R D COVE FLAPJA CK LaGrande dams fail. The Case 1 Lahar inunda on area for POIN T HOG UM Y RD BAY YOU NG TYK LE GREEN NISQ UALLY FLATS CO V E CO V E CO V E NISQ UALL Y HEAD LD B E H LUH R BEACH C A E B D T E S D N U 101 IB ¤£ S U SQU AW B FA LLS POIN T L IS E BEA CH NR SU Historical Occurrences and Impacts K K E SH ELL E E BU TLER C OV E N R N C E POIN T DY D N A MADRONA L CR EEK D BEA C H O OLYMPIA O SH OAL W S CH NE IDE R PR IE ST Thurston County is shown on the map to the right. POIN T M ELLIS UD CO V E SE T CH F I EL D K E BU DD E LA KE R C B IN LET Case 1 Lahar Hazard Area* SUM MI T A R Y E T S LAKE I L L BI G E LO W A LA KE LO C U I SE M LA KE WE ST K E BAY EA ST E R C BAY K E N R RY N PE E E D Y Y TIN WA N AR W I S M O O D QU L A N C D R A E E CAPITOL K 101 L LA K E LAKE L ¤£ LOIS LO S T Y LONGS LA KE POND C R EK E E E SW I F T C R E E K K CR C GOOSE POND KEN A P LA K E I Historically, lahars origina ng from Mount Rainier have been a fairly T 5 8 O L *Source: U.S. Geological Survey Volcano Hazards Program ER LIS T C AL PE R K I N S M L UV AK § TLE CREEK ¨¦ LIT E M C ALLI ST ER CHAMBERS SP R ING S CEDAR FL ATS CR EEK LAK E K E E R LITT LE C CHAMBERS LO NG EEK Based on the Case 1 lahar scenario, proper es along the R LA KE R HI C KS C E T LA KE R O P H C K IT EE D CR E N K A R N L S LO NG A WARD R O W C E S F M LA K E B LA KE M R A H I W C V RT H M NO E R BA R N E S LA K E E L SM I T H K SO U T H W I C K U S L H A LA K E LAKE LA K E A L E N R E ST. R D S CL AIRE E T TR O S P E R HEWITT PATTI SON common occurrence; they vary in size and magnitude and are fairly B C E RE S A E LAKE LA K E LA KE T K T Y D S T C O CREEK HA 1 in = 4.37 miles M PATTI SON K N BE E E R LA K E S T. C LAIRE Y S E Y R D R LA KE C E CREEK LA K E S C SU S A N C R H E I W E U K K E T W E MUN N CR E N S O K S LA K E Nisqually River Valley are the most suscep ble to lahar RI S Y K H C E I L E R A V M H PORT L ER P B TRAI LS EN D E D A C T 510 LA K E R L O E E L N K L E D O R D : E R UV A E V W P I AN R T S L R A Y D M K C C O RE K R EK C N E D A D SUNWO OD E L LAK E K B C D I T C unpredictable. Past Cascade lahars surged nearly 45 to 50 miles per hour O H R H LA K E LU C I N D A A CRE R EK K W E DARLI N E R K SH E E H A N C E E I E LAKE R C N Y SP U RG Y L EO E S N P 9 M S E inunda on. D T I 9 E HO PKIN S K T E E R R C I S DI T C H D N K O REE M C L L SA E R R W A D D D E L L H C O M IT BL O D CLEARWO OD N Y A LA K E M TE M P O R 5 S E C REEK at steep slopes and were 100 feet or more thick. Scien sts have iden fi ed H LAKE S Y E E E C § L ¨¦ L R N E A I E S V K QU L A SC OTT A R L T W L S LA KE L D Y O L I L PI TM A N E I LA K E C OFFUTT LAKE K T R S DE EP D LA KE D D E RI S C S H VER UT E ILVER R S C S R E E PopulaƟ on and Employment in the Hazard Area E K M IM A W C R E E S B E R C K IV E E R I more than 60 lahars that have originated from Mount Rainier in the past D A R S S E A R BEAVER S MU D LA K E D L D CR EEK INMAN C LA K E R R E E R D K R D GEH RKE O Y LA K E A R V R M A A M W W LA K E FIFTE EN H T L S E I I K A I I L I D M S L L L H L S TO A IN R C D 507 MIM R I V E R C V R 10,000 years.