FEMA West Coast Sea Level Rise Pilot Study Ed Curtis, P.E., CFM FEMA Region IX June 4, 2014
Presentation Objectives Present the goals of the FEMA West Coast Sea Level Rise Pilot Study Review the SLR Pilot Study approach Demonstrate our process, present results, and share lessons learned 2
FEMA SLR Pilot Study Goals Determine Future Conditions Base Flood Elevations (BFEs) and flood inundation boundaries for 1%- annual-chance flood total water levels Collaborate with Local Coastal Stakeholders and Federal Peer Review Group Prepare Risk MAP Products Assess Benefits / Costs Contrast with other West Coast SLR studies and viewers Assist San Francisco with incorporating this information into risk assessment and hazard mitigation planning 3
Study Team & Community Staff FEMA Region IX Ed Curtis, Juliette Hayes, Olivia Humilde FEMA Headquarters Mark Crowell, Jonathan Westcott, Tucker Mahoney, Paul Huang City and County of San Francisco (CCSF) Matt Hansen, David Behar PTS Team Vince Geronimo, Darryl Hatheway, Justin Vandever, Jeremy Mull, James Johnston, Erica Harris, Nicole Metzger, Karin Ohman 4
Peer Review (Federal Coordination) Group Mark Crowell, Physical Scientist, FEMA HQ Doug Marcy, Coastal Hazards Specialist, NOAA Coastal Services Center Adam Parris, Physical Scientist & RISA Program Manager Kate White, Sr. Lead for Global and Climate Change, USACE Inst. For Water Resources Patrick Barnard, Coastal Geologist, USGS Coastal and Marine Science Center Chris Weaver, Deputy Executive Director, U.S. Global Change Research Program Brian Batten, Sr. Coastal Scientist, Dewberry 5
CCAMP OPC Overview California Coastal Analysis and Mapping Project - Open Pacific Coast Study Del Norte Restudy current condition coastal flood hazards along CA coastline 15 counties Revise Flood Insurance Rate Maps and establish new BFEs Current condition analysis forms the basis for future condition assessment with SLR Humboldt Mendocino Sonoma Marin San Francisco San Mateo Santa Cruz Monterey San Luis Obispo Santa Barbara Ventura Los Angeles Orange San Diego 6
CA Coastal Flood Characteristics Tides: 6-8 ft tide range Storm Surge: 1-2 ft (max 3 ft) Offshore waves: 10-30 ft, up to 20 second periods Deepwater ocean swell Local winds and seas Strong influence of El Niño/La Niña on storm tracks and water levels 7
Key Concept Total Water Level SWL = Tide + surge (no wave effects) DWL = SWL + wave setup TWL = DWL + wave runup Total Water Level (TWL) Wave Runup Overtopping Dynamic Water Level (DWL) Stillwater Level (SWL) Tide Level Surge Wave Setup Datum 8
SLR Pilot Study and FEMA Pacific Guidelines Linear Superposition Direct Analysis Offshore Zone Shoaling Zone Offshore Waves Wave Transformations Assume negligible SLR effect Offshore Waves Wave Transformations Nearshore Waves Water Levels Nearshore Waves Water Levels + SLR Erosion Coastal Structures Wave Setup Wave Runup Overtopping Erosion Coastal Structures Wave Setup Wave Runup Overtopping Shoreline Change & Profile Adjustment Surf Zone and Backshore Overland Wave Propagation (if necessary) Overland Wave Propagation (if necessary) TWL + SLR TWL Flood Hazard Mapping TWL SLR = TWL + SLR 9 Flood Hazard Mapping TWL SLR > TWL + SLR
Pilot Study SLR Scenarios * Mid-range values for 2050 and 2100 +12 and + 36 High end of range for 2050 and 2100 +24 and +66 * Sea-Level Rise for the Coasts of California, Oregon, and Washington, National Research Council, 2012 10
San Francisco County China Beach (Narrow beach + seawall+ rocky bluffs) Ocean Beach (Wide beach + seawall) San Francisco County Shoreline Ocean Beach (Narrow beach + eroding bluff) 11
Current Condition Mapping Sloat Blvd Armored Low Bluff 1% SWEL = 9.0 ft NAVD 0.2% SWEL = 9.7 ft NAVD 1% Runup (TWL) = 26 ft NAVD 0.2% Runup (TWL ) = 27 ft NAVD No overtopping Bluff Crest at 30-31 ft NAVD 12
Direct Analysis Results Sloat Blvd Armored Low Bluff Current conditions: Peak TWL is ~5 ft below bluff crest 24 SLR: Peak TWL is ~1-2 ft below bluff crest 66 SLR: Many TWL events exceed bluff crest TWL results exhibit nonlinear response to SLR 13
Linear Superposition vs. Direct Analysis Sloat Blvd Armored Low Bluff BFE increase greatly exceeds the linear superposition rate (by a factor of ~2) Wave runup feedback important at this transect Overtopping occurs at much lower SLR under direct analysis vs. linear superposition method 1% TWL Current +24 in +66 in Linear 25.6 ft 27.6 ft 31.1 ft Direct 25.6 ft 29.9 ft 38.5 ft Linear Superposition Direct Analysis SLR (ft) ΔBFE (ft) BFE (ft) 0-25.6 1.0 2.2 27.8 2.0 4.3 29.9 3.0 6.3 31.9 4.0 9.6 35.2 5.5 12.9 38.5 14
Current Condition Mapping Cliff House Natural High Bluff 1% SWEL = 9.0 ft NAVD 0.2% SWEL = 9.7 ft NAVD 1% Runup (TWL) = 25 ft NAVD 0.2% Runup (TWL) = 26 ft NAVD No overtopping Bluff Crest at 60 ft 15
Direct Analysis Results Cliff House Natural High Bluff Bluff crest is not overtopped under current or future conditions Marked increase in TWL due to non-linear increase with SLR 16
Linear Superposition vs. Direct Analysis Cliff House Natural High Bluff BFE increase exceeds the linear superposition rate by a factor of ~3 Wave runup feedback important at this transect 1% TWL Current +24 in +66 in Linear 24.6 ft 26.6 ft 30.1 ft Direct 24.6 ft 30.8 ft 40.7 ft SLR (ft) ΔBFE (ft) BFE (ft) 0-24.6 1.0 3.5 28.1 2.0 6.2 30.8 3.0 8.6 33.2 4.0 11.5 36.1 5.5 16.1 40.7 17 Linear Superposition Direct Analysis
Shoreline Change Static profile (no shoreline retreat) exhibits direct analysis behavior Shoreline retreat mitigates impact of SLR as shoreline adjusts to new equilibrium position Profile erodibility/armoring dictates TWL behavior: direct analysis vs. linear superposition Bluffs, sandy beaches, and structures will exhibit different responses Change in BFE Conceptual Response Non-erodible bluffs, Structures Low erodibility Moderate erodibility High erodibility Sea level rise Sandy beaches, Erodible bluffs 18
Incorporating Shoreline Change Future SFHA Current SFHA TWL + SLR TWL Shoreline Change Buffer MSL Project future TWL onto current condition terrain Buffer SFHA inland by shoreline retreat distance 19
Armored Shoreline Potential Shoreline Retreat 2050 Potential Shoreline Retreat 2100 Potential Shoreline Retreat 20
Unarmored Shoreline with Shoreline Retreat Steep Resistant Bluff Heel of Primary Frontal Dune 21
Stakeholder Feedback Surveyed local, state, and federal stakeholders for input on methods and approach Met with SF Adapt (SLR planning committee) Key feedback: Include two SLR scenarios at each planning horizon (mid-range and high range scenarios). Enhance future rates of shoreline change relative to historical rates. Assume existing structures are maintained in place, Areas for future study (e.g., 500-year event, increase frequency of El Niño events, shoreline change pilot study, etc) 22
West Coast SLR Pilot Study Conclusions Direct analysis approach is superior to linear superposition approach for wave-runup dominated environments (due to increase in toe wave height). Shoreline retreat mitigates non-linear BFE increases. Local stakeholder input on mitigation/ adaptation actions is needed to create credible future conditions maps. Comparison with NOAA and Our Coast Our Future SLR viewers is not complete. 23
Thank You www.r9coastal.org 24
SLR Pilot Study - Points of contact Role Name E-mail FEMA HQ Manager Mark Crowell Mark.Crowell@fema.dhs.gov FEMA Study Manager Ed Curtis Edward.Curtis@fema.dhs.gov Project Manager Vince Geronimo Vince.Geronimo@aecom.com Technical Leads Darryl Hatheway Darryl.Hatheway@aecom.com Justin Vandever Justin.Vandever@aecom.com GIS Lead James Johnston James.Johnston@aecom.com www.r9coastal.org 25
TWL and shoreline response to SLR at beaches At beach and dune shorelines, profile will respond to SLR by shifting landward and upwards With adequate sand supply, profile will maintain shape and position relative to MSL. Will shift vertically by ΔSLR. TWL increase will be linear with SLR Exception: armored shorelines such as seawall-backed beaches TWL SLR = TWL + SLR Bruun Retreat SWL + SLR SWL m f Elev toe Elev toe 26
TWL and shoreline response to SLR at bluffs At bluff-backed shorelines, two key effects of SLR on inundation hazard zones: TWL hazard increase (vertical) Erosion hazard increase (horizontal) Erodible Bluffs Non-Erodible Bluffs (or structures) Rate of SLR matches response time of bluff Bluff retreats to new equilibrium position Elev toe = Elev toe + SLR TWL = TWL + SLR Primary hazard: Erosion Secondary hazard: TWL Retreat Rate of SLR exceeds response time of bluff Bluff retreats minimally and does not reach equilibrium position Non-linear wave runup feedback TWL > TWL + SLR Primary hazard: TWL Secondary hazard: Erosion TWL TWL TWL TWL Elev toe Elev toe Elev toe Elev toe 27
West Coast SLR Studies - Examples California / West Coast SLR Studies Our Coast Our Future (OCOF) using CoSMoS; SCC Southern CA SLR Study using CoSMoS; Adapting to Rising Tides (SF Bay); Coastal Resilience Ventura; Sea Level Rise Adaptation Strategy for San Diego Bay; Humboldt Bay Shoreline Inventory, Mapping, and Sea Level Rise Vulnerability Assessment; NRC Sea Level Rise Study for the West Coast; Sea Level Rise City of Newport Beach Approach for Balboa Island Adapt LA San Francisco SLR Studies SPUR Ocean Beach Study Port of San Francisco SLR and Climate Adaptation Plan SFPUC Climate Adaptation Plan Mission Bay SLR Study SFO SLR Vulnerability Assessment and Feasibility Study 28
Key FEMA SLR Web Tools Our Coast Our Future (OCOF) (San Francisco Bay Area) http://data.prbo.org/apps/ocof/ NOAA Digital Coast Sea-Level Rise Viewer http://www.csc.noaa.gov/slr/viewer/# Cal-Adapt - Exploring California s Climate http://cal-adapt.org/sealevel/ Pacific Institute Sea-Level Rise Maps http://www.pacinst.org/reports/sea_level_rise/maps/ Climate Central Surging Seas http://sealevel.climatecentral.org/ California Energy Commission; UC-Berkeley Geospatial Innovation Facility http://cal-adapt.org/sealevel/ 29
San Francisco SLR Pilot Study Mapping Conclusions Conducted comparison with NOAA SLR Viewer and USGS Our Coast Our Future mapping methods and results Developed method to buffer SFHA to account for shoreline change and visualize landward increase in extent of SFHA Shifted mapping focus from paper maps to digital non-regulatory RiskMAP products and online viewer Mapping level of effort may increase greatly for higher SLR scenarios due to increased instances of overtopping Major challenge: Difficult to create credible future conditions maps without local stakeholder input on mitigation/adaptation actions 30