San Luis Obispo County December 2, 2014

Transcription

1 Flood Risk Review Meeting: Open Pacific Coast Study San Luis Obispo County December 2, 2014

2 Welcome and Introductions Flood Risk Review Meeting San Luis Obispo County California Coastal Analysis and Mapping Project Open Pacific Coast Study Federal Emergency Management Agency - Region IX Edward Curtis, PE, CFM Regional Engineer Study Manager Olivia Humilde External Affairs/Mitigation Outreach Specialist Juliette Hayes Mitigation Planning Program Lead Edith Lohmann National Flood Insurance Specialist Gregor Blackburn Floodplain Management & Insurance Branch Jane Hopkins Natural Hazards Program Specialist FEMA Production and Technical Services Contractor Vince Geronimo, PE, CFM Project Manager Darryl Hatheway, CFM Technical Lead, Justin Vandever, PE Coastal Engineer James Johnston, GISP, CFM GIS Manager & Wendy Chang Community Outreach San Luis Obispo County, City of Grover Beach, City of Morro Bay, & City of Pismo Beach 2

3 Why We re Here Provide an overview of FEMA s National Flood Insurance Program (NFIP) Risk Mapping, Assessment and Planning (Risk MAP) Program Open Pacific Coast (OPC) Study Review FEMA s Coastal study process and methodology draft Work Maps Online tool for review and comments Discuss how FEMA products and datasets can Support your flood risk communication Inform decisions to reduce flood risk Answer your questions 3

4 National Flood Insurance Program & Risk MAP

5 National Flood Insurance Program U.S. Congress established the National Flood Insurance Program with the passage of the National Flood Insurance Act of 1968 Community adopts and enforces a floodplain management ordinance to reduce flood risk to new and existing development in mapped floodplains Federal government makes flood insurance available to property owners in participating communities For more information on the NFIP visit 5

6 Risk MAP Vision To deliver quality data that increases public awareness and leads to action that reduces risk to life and property Objective (Coastal) To provide updated flood hazard data for 100% of the populated U.S. coast 6

7 What is a FEMA Flood Insurance Rate Map (FIRM)? 7

8 Open Pacific Coast Study

9 California Coastal Analysis and Mapping Project Two Companion Large-Scale Efforts: Open Pacific Coast (OPC) Study San Francisco Bay Area Coastal (BAC) Study Re-study flood risk along the open coast and inland bays of all California coastal counties Re-map the elevation and inland extent of wave-induced coastal flooding 9

10 Overall OPC Study Schedule OPC Study Phase 2 includes Southern California Counties 10

11 Outreach Timeline for Community Floodplain Manager April 2011 Discovery Meeting SLO County Study Kick-off Flood Risk Review Meeting Discuss coastal analysis and review draft work maps Outreach Timeline Open Pacific Coast Study Today April 2015 Resilience Workshop Implement actions to mitigate or reduce coastal flood risks July 2015 Preliminary FIRM Meeting Open House Public Meeting Provide Study Data Work Map Comment Tool Develop Community Outreach Plan Implement Outreach Plan Data Acquisition Coastal Analysis Floodplain Mapping Prelim. Map Production Post Prelim Process Map Production Timeline Typical Coastal Flood Study Proposed Flood Hazard Determinations Appeal Period Issue Letter of Final Determination (LFD) Effective Maps Physical Map Revision (PMR) ~ December

12 Coastal Study Process

13 Coastal Study Process O U T R E A C H T A P R E V I E W Discovery Data Acquisition/Processing Engineering Analyses Floodplain Mapping Map Production Scoping Meetings (Initiate Outreach, Kick-off Meeting, Field Recon) Data Acquisition (LIDAR, Tide Records, Offshore Waves, Bathymetry) Engineering Analyses (Wave Setup, Wave Runup, Dune Erosion) Draft Work Maps Post-Preliminary Processing 13

14 Post Prelim Mapping Process Map Production Preliminary maps Community review Preliminary FIRM meeting Post-Prelim Processing Statutory process for proposed BFE Map adoption: 6-month compliance period Maps become Effective Preliminary Maps Post-Preliminary Processing Community Review Preliminary FIRM Meeting BFE Docket Preparation and Appeal Period Final Map Preparation and Issue Letter of Final Determination Compliance Period (Map panels adopted by ordinance) 30 Days or Days More + 90 Days 90 Days 6 Months Community Meetings Revised maps become effective Resilience Meeting 14

15 Coastal Study Process Intermediate Data Submittals (IDS) IDS #1 Scoping and Data Review Field reconnaissance Technical approach Data sources IDS #2 Offshore Waves and Water Levels Deepwater wave climate Nearshore wave transformation Extreme stillwater (SWEL) analysis Stillwater level (SWL) reconstruction IDS #3 Nearshore Hydraulics Wave setup, runup, and overtopping analysis Evaluation of coastal structures IDS #4 Draft Flood Hazard Mapping Determination of flood hazard areas Draft Work Maps 15

16 Field Reconnaissance 16

17 Data Acquisition & Processing Topography and Bathymetry Collection California Coastal Mapping Program Ocean Protection Council NOAA USGS Terrain Development Build merged bathymetric and topographic terrain model for 1-D transectbased wave analysis Bathymetry LiDAR 17

18 Coastal Study Process 1-D Transectbased Analysis 18

19 Data Acquisition & Processing Offshore Water Levels 50-year ( ) hourly stillwater level (SWL) time series Rely on long-term observed tide station records where available Use predicted tide data and adjacent station data to fill gaps Extreme tide frequency analysis for stillwater elevations (SWEL) Based on observed annual maxima tide data 50-, 20-, 10-, 4-, 2-, 1-, and 0.2- percent annual chance SWELs 19

20 Data Acquisition & Processing Deepwater Wave Hindcast (OWI) Oceanweather Inc. Global Reanalysis of Ocean Waves (GROW) Model 50-year hourly hindcast of waves ( ) COASTAL model provides wave spectra at 124 grid point locations Extensive validation with buoy data Model output points GROW GROWFine: NEPAC 20 COASTAL Model

21 Data Acquisition & Processing Nearshore Wave Transformation Scripps Institution of Oceanography SIO SHELF linear spectral refraction and shoaling model from deepwater to surf zone (15m water depth in San Luis Obispo at 200 m spacing) 50-year hourly hindcast of nearshore waves ( ) Model validation with buoy data Wave height and peak direction 21

22 1-D Coastal Hazard Analyses Transect-based analysis 79 analysis transects Transect locations and density based on: Shoreline characteristics Shoreline orientation Nearshore bathymetry Wave climate Land use and development 22

23 Total Water Level Components of the total water level (TWL) Astronomical tide (predicted tide): 5-7 ft Surge components: atmospheric pressure, wind setup, El Niño sea level effects: 1-3 ft Wave components: wave setup + runup: ft SWL = Tide + surge (no wave effects) TWL = SWL + setup + runup Total Water Level (TWL) Wave Runup Overtopping Dynamic Water Level (DWL) Stillwater Level (SWL) Wave Setup Tide Level Surge Datum 23

24 Analyzing Wave Setup, Runup, and Overtopping Setup and Runup Methods Stockdon (2006): sandy beaches and dunes with slope < 1:9 DIM (Pacific Guidelines): rocky beaches with slope > 1:9 DIM + TAW (van der Meer): steep barriers (bluff, seawalls, and revetments) Overtopping Method Cox-Machemehl (inland extend of high velocity zone beyond crest) Dune Erosion Method MK & A geometric dune erosion model Kriebel and Dean time dependence adjustment Extreme Value Statistical Analysis Primary: Peaks-over-threshold (POT) with Generalized Pareto Distribution (GPD) Secondary: Annual maxima (AM) with Generalized Extreme Value Distribution (GEV) 24

25 Estimating Extreme TWLs TWL (ft NAVD) 1-percent TWL TWL time series is computed for 50-year hindcast period Peak TWLs values are extracted for extreme value statistical analysis EVA to determine: 50-, 20-, 10-, 4-, 2-, 1-, and 0.2- percent annual chance TWLs 25

26 Morro Bay Sheltered Waters Wave Hazards Morro Bay is sheltered from open coast swell. Moderate fetch can generate local wind waves inside bay. Assess wave growth using ACES and FEMA s Sheltered Waters Guidance Wind and Water Level Forcing Reviewed wind data from San Luis Obispo down to Point Arguello 45-mph wind speed from N, NW, and W were selected Analysis assumed 1% SWEL Overland Waves and Runup WHAFIS and TAW used for overland waves and wave runup calculations Event-based analysis to determine BFE 26

27 San Luis Obispo Harbors Wave Hazards in Harbors Wave transmission over breakwater (Diablo Canyon) Wave diffraction around breakwater tip (Port San Luis) No detailed modeling performed inside harbor Response-based analysis using transmitted or diffracted wave height Runup on inland shoreline in protected area to determine BFE 27

28 Coastal Structures Wide variety of coastal structures present along CA coast BakerAECOM reviewed: LiDAR, as-builts from community, aerial photos, site visit notes, USACE drawings and surveys, and Coastal Commission GIS layers to identify and represent structures in profile Rip-rap Grouted rock armor Seawall Revetment 28

29 Coastal Structures BakerAECOM developed global treatments to guide decisions at each site based on FEMA s Pacific Guidelines and USACE guidance Consider historical performance, structure condition, as-built drawings, maintenance history, certification, permits, and engineering judgment Will structure withstand base flood event? Yes Conduct Intact analysis only No or uncertain Conduct Intact and Failed Analysis Failed Analysis = partial failure or removal, depending on site conditions Map the most hazardous Base Flood Elevation only 29

30 Flood Hazard Mapping Special Flood Hazard Area (SFHA) Mapping Zone VE: Inundated by 1-percent annual chance flood with additional waveinduced hazards (wave runup, wave overtopping splash, high velocity, or overland wave propagation); detailed Base Flood Elevation (BFE) Zone AE: Inundated by 1-percent annual chance flood; detailed BFE Both high hazard zones carry mandatory flood insurance purchase requirements Zone X (shaded): Inundated by 0.2-percent annual chance flood (or inundated by <1 ft for 1-percent flood) Coastal High Hazard Areas Wave Crest Profile Zone VE Zone AE Zone X SWEL Shoreline at map datum H = 3 ft SFHA Boundary 30

31 Primary Frontal Dune V Zone Mapping Primary Frontal Dune (PFD) V Zone Mapping Definition: a continuous or nearly continuous mound or ridge of sand with relatively steep seaward and landward slopes immediately landward and adjacent to the beach and subject to erosion and overtopping from high tides and waves during major coastal storms Landward extent: a point where there is a distinct chance from a relatively steep slope to a relatively mild slope (i.e., the dune heel) Implications: The PFD represents the landward extension of the VE Zone Purpose: Floodplain management tool to protect dunes and regulate coastal construction practices and building standards Delineation of the PFD is mandated by FEMA regulations Primary Frontal Dune Delineation Crest 1% TWL SWL Limit of runup Toe Primary Frontal Dune Dune Width Heel VE Zone PFD at Pismo Beach 31

32 Analysis and Mapping Examples Example Locations Transect 117 (seawall + bluff; intact scenario) Transect 399 (sandy beach + seawall; map wave runup hazard inland to seawall) Transect 85 (sandy beach + dune; PFD delineation) Transect 160 (armored bluff; structure removal; overtopping hazard zone)

33 Seawall + Bluff Transect 117 Coastal Analysis Results 1% SWEL = 7.8 ft NAVD 0.2% SWEL = 8.2 ft NAVD 1% Runup (TWL) = 18 ft NAVD 0.2% Runup (TWL) = 23 ft NAVD Overtopping distance from crest = N/A (TWL projects onto bluff) VE (EL 18) 33

34 Sandy Beach + Seawall Transect 399_001 Coastal Analysis Results 1% SWEL = 7.8 ft NAVD 0.2% SWEL = 8.2 ft NAVD 1% Runup (TWL) = 15 ft NAVD 0.2% Runup (TWL ) = 16 ft NAVD Overtopping distance from crest = N/A Map runup hazard zone (VE) to seawall VE (EL 15) Monterey Beach Resort 34

35 Sandy Beach + Dune Transect 85 VE (EL 15) Coastal Analysis Results 1% SWEL = 7.8 ft NAVD 0.2% SWEL = 8.2 ft NAVD 1% Runup (TWL) = 15 ft NAVD 0.2% Runup (TWL ) = 17 ft NAVD Overtopping distance from crest = N/A Primary Frontal Dune (PFD) V Zone Mapping to heel of dune Pismo State Beach 35

36 Armored Bluff + Overtopping Transect 160 Coastal Analysis Results 1% SWEL = 7.8 ft NAVD 0.2% SWEL = 8.2 ft NAVD 1% Runup (TWL) = 28 ft (failed) or 23 (intact) ft NAVD 0.2% Runup (TWL ) = 34 ft (failed) or 29 (intact) ft NAVD Overtopping distance from crest = 25 ft (failed case) VE (EL 28) Port San Luis 36

37 Structure Removal at Armored Bluff Transect 160 Legend Existing revetment Underlying natural bluff profile Profile features for intact profile Profile features for removed structure profile DWL2% Existing Revetment E j Project MSL-E j slope landward from E j E edge E edge E j E crest, E crest m face 1.5:1 Project 1.5:1 seaward from E edge Identify projected toe, E j Bracket the TWL response with two cases Identify toe, edge, and crest of intact profile Compute TWL for intact case (with roughness reduction) Remove structure from profile Compute TWL for failed case (without roughness reduction) 37

38 Armored Bluff + Overtopping Transect 160 Special Flood Hazard Area (SFHA) Mapping Three hazard zones identified at this transect (for failed scenario): Wave runup hazard zone: VE = 28 ft NAVD Overtopping hazard zone: VE = 18 ft NAVD Inundation hazard zone: AO (1 ft depth) Crest elevation, E crest = 11.6 ft NAVD Initial bore height, h 0 = 6.3 ft Bore elevation = = 17.9 ft NAVD 28 ft 18 ft AO (1 ft) 38

39 Hazard Mitigation Planning

40 Hazard Mitigation Planning What is Hazard Mitigation? Any sustained action taken to reduce or eliminate long-term risk to human life and property from hazards What is a Hazard Mitigation Plan? A single/multi-jurisdictional plan that identifies, assesses, evaluates, and prioritizes hazards of all kinds and prescribes mitigation actions. 40

41 Plan Updates and Implementation Risk MAP Data Meetings and Coordination Areas of Mitigation Interest Local Plans Planning Team Risk Assessment Mitigation Strategy Benefit Cost Analyses Local Coastal Program Local Actions Codes and policies Property Protection Communication and Coordination 41

42 Hazard Mitigation Plans San Luis Obispo Community Plan Status Local Jurisdiction Plan Type Approved Until Current Status San Luis Obispo (Unincorporated Areas) Single-Jurisdiction 12/2/2016 Approved City of Grover Beach Multi-Jurisdiction 3/4/2013 Expired / New plan submission pending awaiting revision from City City of Morro Bay Single-Jurisdiction 1/23/2012 Expired City of Pismo Beach Single-Jurisdiction 3/29/2012 Expired Hazard Mitigation Plans are required to be updated every 5 years 42

43 Next Steps FEMA Post the work maps on-line for review and comment at Produce Preliminary Maps and facilitate Resilience Workshop Community Officials Review and comment on the draft work maps Stay Informed throughout the Study Sign up for the Coastal Beat E-newsletter and additional FEMA resources Consider using OPC data for hazard mitigation plan update 43

44 Stay Informed Throughout the Study Meetings Materials Study Updates Website: 44

45 FEMA Region 9 Webpage FEMA Resources Follow FEMA R9 via Sign up for FEMA Updates at Topics: Region 9 NFIP / CCAMP / Region 9 Risk MAP Sign up for the California Coastal Analysis and Mapping Project (CCAMP) E-newsletter at FloodSmart: floodsmart.gov - Get a quote, Find an agent Flood Map Service Center: - Print FREE flood maps for your community Ready.gov, Listo.gov, Ready.gov/business - Fact sheets, links to training 45

46 Online Work Map Commenting Tool

47 Flood Risk Review & Comment Tool Post draft Work Maps online at for community review Accommodate community staff need to review data beyond the meeting timeframe Reduce paper map products from the workflow and reduce the potential for lost comments 47

48 Comment Process Work Maps released for review in January 2015 Users will be provided a unique login and password WebEx-based demo on the launch date Works Maps will be available for 30 days All comments will be recorded and archived 48

49 Work Map Review

50 Questions & Answers

51 Back-up Slides

52 Coastal Non-Regulatory Products Non-regulatory products supplement information on the FIRM. They work alongside the regulatory products to provide additional flood risk information and help plan for resilience. Types of Non-regulatory products: Flood Risk Map, Flood Risk Report, and Flood Risk Database Changes Since Last FIRM Areas of Mitigation Interest Flood Depth and Analysis Grids Increased Flooding Scenarios (BFE + 1 ft, BFE + 2 ft, BFE + 3ft ) Dune Size and Location Simplified Coastal Zones Flood Risk Assessment Data Coastal-Specific Non-regulatory Datasets (FEMA, May 2014) 52

53 Coastal Non-Regulatory Products 53