San Francisco Bay Area Coastal StudyCalifornia Coastal Analysis and Mapping ProjectSeptember 2012

2 San Francisco Bay Area Coastal Study California Coastal Analysis and Mapping Project | FEMA 3

San Francisco Bay Area Coastal Study and Mapping OverviewThe Federal Emergency management Agency (FEMA) is performing new detailed coastal engineering analyses of the shoreline and coastal areas within the nine counties of: • Alameda• Contra Costa• Marin • Napa• San Francisco• San Mateo• Santa Clara• Solano• Sonoma

Thenewcoastalstudywillreviseandupdatethefloodandwavedatafor the coastal Flood Insurance Study reports and Flood Insurance Rate Maps for each of the above counties.

FEMA’scoastalstudyandmappingeffortsbenefitfromnewtechnologies and coastal data, including the latest 2010 detailed topographic data collected as part of the California Coastal Mapping Program.Thecoastalfloodhazardanalysesuseregional-scalestormsurge and wave models of San Francisco Bay. These models produce time-seriesoutputofwaterlevels,openoceanswells,andwind-drivenwaves at over eight thousand points along the complex San Francisco Bayshoreline.Inputparameterstotheregional-scalemodelsincludeocean tide levels, lower Sacramento River discharges, wind and pressurefields,andvariousriverandcreekdischarges.

The model output from the regional models is used to estimate wave runup and overtopping along the Bay’s myriad of shoreline structures and steep shorelines, as well as overland wave propagation over beaches, marshes, and inland developed areas. These onshore analyses will form the basis for potential revisions to the Base Flood Elevations (BFEs)andSpecialFloodHazardAreas(SFHAs)withinthecoastalareasofthenineBayAreacounties.CoastalHighHazardAreas(ZoneVE)willbemappedwhensupportedbyfloodhazardmodelingresults.

The US Army Corps of Engineers is also conducting coastal analyses within San Francisco Bay, and these studies will be evaluated for compatibility with FEMA’s study and mapping goals.

Following FEMA’s due process and statutory requirements, the BFE’s willbefinalizedinrevisedFloodInsuranceStudyreportsandontheFlood Insurance Rate Maps. FEMA is coordinating with Federal and Stateentities,wewellasregionalandlocalstakeholders.FEMAwillcontinuetocoordinatewiththesestakeholdersasthestudyandmapping efforts progress.

Next Steps, Stay Informed and EngagedAfterFEMA’sreviewandapprovalofthecoastalfloodhazardanalysis,itwillcommencewiththefloodplainmappingonacounty-by-countybasis.FEMAwillscheduleaFloodRiskReviewmeetingwitheachBay Area county during this phase of the study. The goal of the Flood RiskReviewmeetingistoenhancethecommunitiesunderstandingoftheavailablefloodriskdatasets,todiscussstudymethodsandresults,andtoprovideinformationonincreasingriskawarenessandstimulatingmitigationactionsthatcanreducerisk.

To stay up to date with the San Francisco Bay Area Coastal Study, and thecompanionOpenPacificCoaststudy,signupforthequarterlye-bulletin,Coastal Beat, that will include schedule updates, technical articles and facts of interest, and relevant information as the study progresses.Visitwww.r9coastal.org for additional coastal study information. Stay informed and engaged in FEMA’s coastal studies by signing up for RSS feeds from this site to receive updates delivered directlytoyouremailinbox.FEMAwelcomesyourfeedback,questionsand comments.

San Francisco Bay Counties

California Coastal Analysis and Mapping Project

San Francisco Bay Area Coastal Study Mapping Timeline

This publication is an initiative of the Mitigation Division of FEMA Region IX.

National Flood Insurance Program

Discovery Map: Los Angeles County

6 San Francisco Bay Area Coastal Study California Coastal Analysis and Mapping Project | FEMA 7

Coastal Flood Issues in the San Francisco Bay AreaTypes of Flooding

Annual High Tide Inundation (“King Tides”)• Howitworks:KingTidesareabnormallyhighpredictableastronomicaltides

thatoccurapproximatelytwiceperyearwithinSanFranciscoBay.KingTidesarethe highest tides that occur each year and typically exceed 7 ft Mean Lower Low Water (MLLW) at the Presidio tide station.

• ExampleEvents:KingTidesoccureveryyearduringthewinter,typicallyduringthe months of December, January, and February.

• TypesofImpacts:Nuisanceflooding;inundationoflow-lyingroads,boardwalks,andwaterfrontpromenades;canexacerbatecoastalandriverineflooding.

• LocationofImpacts:HWY101off-rampatMillValley,Sausalitowaterfront,andRichardsonBayshorelineinMarinCounty;Embarcaderowaterfront(Pier14)andMarinaareainSanFrancisco;andBayBridgeTollPlazafrontageroadandJackLondonSquareinAlamedaCounty.

El Niño Winter Storms• Howitworks:DuringElNiñowinters,atmosphericandoceanographic

conditionsinthePacificOceanproduceseverewinterstormsthatimpacttheSanFranciscoBayregion.PacificOceanstormsfollowamoresoutherlyrouteand bring intense rainfall and storm conditions to the Bay area. Riverine and coastalfloodingoftencoincideandproduceupstreamflooding.Tidesareelevated by approximately 0.5 to 1.0 feet above normal along the coast and wind setup can elevate water levels even further locally.

• ExampleEvents:Wintersof1977-1978;1982-1983;1997-1998;2009-2010.• TypesofImpacts:Severeinundationoflow-lyingroads,boardwalks,and

waterfrontpromenades;combinedriverineandcoastalflooding;wavedamageto coastal structures.

• Location of Impacts: Throughout the Bay, particularly along developed shorelinesandtidallyinfluencedcreeksandsloughspronetohightideflooding.

Extreme High Tide Inundation • Howitworks:WhenPacificOceanstormscoincidewithhightides,stormsurge

due to meteorological effects can further elevate San Francisco Bay water levels toproduceextremehightides.ElNiñoconditionsalongtheCaliforniacoastcanalso contribute to storm surge and produce extraordinarily high water levels.

• ExampleEvents:January27,1983(8.66ftMLLW);December3,1983(8.65ftMLLW);February6,1998(8.38ftMLLW);January8,2005(8.14ftMLLW);December31,2006(8.09ftMLLW).

• TypesofImpacts:Severeinundationoflow-lyingroads,boardwalks,andwaterfrontpromenades;canexacerbatecoastalandriverinefloodingandcauseupstreamflooding;caninterferewithstormwateroutfalls.

• Location of Impacts: Throughout the Bay, particularly along developed shorelinesandtidallyinfluencedcreeksandsloughspronetohightideflooding.

Wind Wave Events• Howitworks:StrongwindsduetoPacificOceanstormsorstrongthermal

gradients produce strong winds that blow across the Bay. When the wind blows over long reaches of open water large waves can be generated that impact the shoreline and cause damage.

• ExampleEvents:PacificOceanwinterstormevents;pre-frontalsoutherlywinds;northerly thermal winds.

• Types of Impacts: Wave damage along the shoreline, particularly to coastal structuressuchaslevees,docksandpiers,wharfs,revetments;backshoreinundation due to wave overtopping of structures and ponding. Impacts can beexacerbatedbyhightideswhichlimitswavedissipationovermudflatsandmarsh.

• Location of Impacts: Exposed shorelines with expansive wind fetches, particularly along the East Bay shoreline.

Front and Back Cover Photos:Copyright©2010-2011Kenneth&GabrielleAdelman,CaliforniaCoastalRecordsProject,www.californiacoastline.org

www.fema.gov/plan/prevent/fhm/rm_main.shtm·1–877–FEMAMAP

Points of Contact

For more information on the California Coastal Analysis and Mapping Project (CCAMP) visit: www.r9coastal.org

Contact:KathySchaeferFEMA Study ManagerKathleen.Schaefer@fema.dhs.gov

Role Name Phone Number E-mail

FEMA Study Manager KathySchaefer (510)627-7129 Kathleen.Schaefer@fema.dhs.gov

Study Project Manager KrisMay (510)622-6640 Kris.May@aecom.com

North Bay Technical Lead Brad Hall (916)371-7400 BHall@nhcweb.com

Central Bay Technical Lead KristaConner (215)446-5190 KLConner@mbakercorp.com

South Bay Technical Lead Darryl Hatheway (619)905-9488 Darryl.Hatheway@aecom.com

Outreach Coordinators Wendy Chang (510)844-0576 Wendy.Chang@aecom.com

Lisa Messano (510)879-0911 LMessano@mbakercorp.com

GISManager James Johnston (510)879-4539 James.Johnston@aecom.com