Coastal Flood Insurance Studies in Virginia and Climate Change

Transcription

1 Coastal Flood Insurance Studies in Virginia and Climate Change VFMA Floodplain Management Workshop October 22, 2015 Jeff Gangai

2 Why is a Coastal Restudy Needed? New Guidelines need to be implemented Atlantic Ocean and Gulf of Mexico Guidelines Update (2007) Sheltered Waters Report (2008) PM 50 Limit of Moderate Wave Action (LiMWA) (2008) and new 2013 OG To update base data such as topographic dataset and aerial imagery to high resolution products and seamless Digital Elevation Model (DEM) To utilize newer coastal hazard methodologies developed during the FEMA Mississippi Coastal Restudy To take advantage of higher performance numerical modeling To take advantage of improvement in GIS technologies to allow for more precise FIRMs 2

3 Modern GIS-Integrated FIS Modeling 3

4 Technology = Efficiency = Increased Precision Example, Suffolk County, NY 1,200 miles of ocean and estuarine shoreline Existing FIRM = 208 coastal transects GeoCoastal application allowed 1611 transects for typical study budget 670% increase in resolution Results easier to defend due to detail of analysis 4

5 Map Modernization New digital FIRMs more precisely represent current flood risk Countywide digital FIRMS easier to use and update 98% of communities in Region III now have digital FIRMs 5

6 Why is a Coastal Restudy Needed? 6

7 Region III Coastal Study Timeline Surge Study Results Winter 2011 Coastal Hazard Analysis Results Spring Summer 2014 Preliminary FIRMs Summer 2013 Spring 2015 Letter of Final Determination Spring 2014 Winter 2015 New Effective Coastal FIRMs Fall 2014 Summer

8 Coastal FIS Project Life-cycle 8

9 Region III Coastal FIRM Status (Hampton Roads) Gloucester 11/19/2014 Newport News 12/09/2014 Chesapeake, Poquoson 12/16/2014 Virginia Beach, York 01/16/2015 Surry 05/04/2015 Suffolk, Portsmouth 08/03/2015 Isle of Wight 12/02/2015 James City/Williamsburg 12/16/2015 Hampton 05/16/2016 Norfolk 90-day appeal period ended September 2015 (1 appeal received) 9

10 FEMA REGION III COASTAL STORM SURGE STUDY Jeff Hanson, Ph.D. Project Leader Mike Forte Project Specialist 10

11 FEMA Region III Study Area Four states plus District of Columbia Five metropolitan areas Complex coastal geomorphology Delaware River/Bay system - Tidal up to Trenton, NJ square mile bay - Strategic shipping and military port Chesapeake bay - Third largest estuary in world - 11,000 miles of tidal shoreline - Major shipping, seafood and military ports 11

12 Storm Surge Study Approach Storm Forcing Extratropical Wind Fields Hurricane Tracks High-Resolution Bathymetry/Topography Storm Surge Modeling Winds Wave s Water Levels Statistical Analysis completed in order to determine Return Period 10%, 2%, 1% and 0.2% annual chance stillwater elevations 12

13 Improvement in Modeling Capabilities Current stillwater elevations (SWELs) on FIRMs date back to (few updates made in early-1990s) and were computed using a tidal gage analysis or the Virginia Institute of Marine Sciences (VIMS) model 1978 Mesh 3-6 mile resolution 2011 Mesh 100 ft Minimum Resolution 13

14 Modeling System Validation Validation Storms Hurricane Isabel (SEP 03) Hurricane Ernesto (AUG 06) Extratropical Storm Ida (Nov 09) Hurricane Isabel September 2003 Validation Parameters Tides Hurricane Ernesto (AUG 06) Wind speed and direction Water levels High water marks 14

15 High Water Marks: Hurricanes Isabel and Ernesto Hurricane Isabel September 2003 Extra-tropical Storm Ida November 2009 Circles depict observed high water marks to same color scale as background surge predictions 15

16 Production Run Storms Extratropical Storms February 4, 1998 Pressure Field 30 Top ranked storms Based on water levels at 10 stations Careful reanalysis of wind/pressure fields Tropical Storms Record of 20 hurricanes in 60 years insufficient for 100- yr analysis 156 Representative events sampled from ASCE 100,000-year synthetic storm set 156 Simulated Hurricane Tracks A 1-year effort! Intensities range from Tropical Storm to Cat 3 Demonstrated validity with comparisons to historic data 16

17 Tidal Contributions Average High Tide Elevation MHHW above MSL (m) 17

18 Updated SWEL Hurricanes Extratropicals Combined Elevation (ft, MSL) 18

19 Hampton Roads Area Difference between updated and published 100-yr SWELs (ft) (Updated published) Orange: 1-2 ft higher Green: Less than 1 ft change Blue: 1-3 ft lower 19

20 Coastal Study Resources - Storm Surge Study 1.1 DEM 1.2 Modeling System 1.3 Storm Forcing 2. Model Validation 3. Final Analysis Coastal Storm Surge Analysis: Final Report Methods and results Released as formal reports Available at or 20

21 Coastal Study Process TERRAIN PROCESSING STORM SURGE ANALYSIS STARTING WAVE CONDITION ANALYSIS TRANSECT LAYOUT & FIELD RECONNAISSANCE FRONTAL DUNE DELINEATION STORM-INDUCED EROSION OVERLAND WAVE HEIGHT & RUNUP ANALYSIS FLOODPLAIN BOUNDARY & FLOOD HAZARD ZONE MAPPING 21

22 Transect Placement Transect Layout City of Virginia Beach 22

23 Overland Wave Hazard Modeling Storm-induced erosion Primary frontal dunes Erodible bluffs WHAFIS 4.0 Profile elevation 1% SWELs Starting wave conditions Wave Setup Obstruction cards (OF, IF, BU, VE, MG) 23

24 Field Reconnaissance 24

25 Field Reconnaissance Efforts DRAFT 25

26 Obstructions Ready for Modeling 26

27 Erosion Analysis Dunes: Dune erosion based on the 540 sqft rule Dune retreat Dune removal Primary Frontal Dune (PFD) delineation 27

28 Primary Frontal Dune Line Drawn Based on Aerial Images and Information Obtained from Field Reconnaissance 28

29 Shoreline Protection and Wave Runup Shoreline Protection Structures: Will the shoreline protection structure survive the 1% event? Is the structure certified? Modeling of integral structure vs. fail structure to determine higher hazard FEMA 2007 Guidelines now requires the use of the 2% runup vs. the mean runup computed prior to 2007 Mild-sloping beaches, bluffs and cliffs Methods: CSHORE 1-D, Runup 2.0, TAW, SPM 29

30 Basic Elements of a Coastal Hazard Analysis Base Flood Elevation on FIRM includes 4 components: 1. Storm surge stillwater elevation (SWEL) 2. Amount of wave setup 3. Wave height above storm surge (stillwater) elevation Determined from storm surge model 4. Wave runup above storm surge elevation (where present) 30

31 Mapping 31

32 Limit of Moderate Wave Action (LiMWA) FEMA Procedure Memorandum No. 50, 2008 At present not a regulatory requirement No Federal Insurance requirements tied to LiMWA CRS benefit for communities requiring VE Zone construction standards in areas defined by LiMWA or areas subject to waves greater then 1.5 ft. FEMA OG No Updated Guidance for Identification and Mapping of LiMWA (October, 2013) 32

33 Coastal Study Resources FIS Report Coastal TSDN FEMA Map Service Center Website Property Locator Tool All content transferred to riskmap3.com 33

34 FIS Report Starting Point of Transect (at shoreline) Overland Modeling Input Parameters for Transect (at shoreline) 34

35 TSDN Data and Report Detailed methods in Report County/Citywide stillwater surfaces (10%, 2%, 1%, & 0.2%) Modeling Geodatabase with published and mapping transects Transect and obstruction GIS layers Model input parameters and results CHAMP database/whafis input and output files Wave runup and overtopping analyses Mapping Geodatabase Floodplain boundaries (1% and 0.2%) V/A zone boundary Zone gutters/divisions and labeling 35

36 Potential for Ongoing and Future Work SLR studies Assessment of flood protection strategies Design parameters for shoreline protection structures Suitability of living shorelines Boundary conditions for refined regional or local coastal models Establishment of tailwater conditions for stormwater models Floodplain mapping changes for Flood Mitigation Efforts (CLOMR and LOMR) 36

37 Future Updates to Studies Coastal Coordinated Needs Management System (CNMS) Every 5 year evaluate validity of Coastal Study and Mapping on FIRMs Elevation & Bathymetry Data Land Use Modeling Technology Guidelines and Methods Historic Storms Damage Storm Frequency Shoreline Position (Long-term erosion) Water levels (sea level rise/lake level) 37

38 Ongoing Work - Additional Risk MAP Products Traditional Regulatory Products Non-Regulatory Products DFIRM Database Traditional products are regulatory and subject to statutory dueprocess requirements Risk MAP products are non-regulatory and are not subject to statutory dueprocess requirements 38

39 Non-Regulatory Coastal Flood Risk Products and Datasets Flood Risk Products Flood Risk Report Flood Risk Database Flood Risk Map Flood Risk Datasets Changes Since Last FIRM Coastal Depth Grids Flood Risk Assessment (refined Hazus analysis) Areas of Mitigation Interest Flood Risk Products help communities: Gain a better understanding of flood risk and its potential impact on communities and individuals Take proper mitigation actions to reduce this risk 39

40 Coastal Increased Inundation Areas Legend COASTAL INCREASED INUNDATION base + 1 foot base + 2 foot base + 3 foot 40

41 Virginia s Relative Exposure to SLR National Rankings Change in hazard/exposure for 2060 due to SLR State Change in Population from Baseline Change in Housing Units from Baseline Area within Coastal SFHA Change in Area from Baseline FLORIDA NEW YORK LOUISIANA NEW JERSEY TEXAS VIRGINIA CALIFORNIA Based on low SLR projection FEMA Programmatic Environmental Impact Statement 41

42 Why is Climate Change important to NFIP? As of October 2013, NFIP currently has: About 5.6 million policies in force $1.3 trillion coverage in force $24 billion debt to U.S. Treasury Coastal Floodplains expected to increase by up to 55% by 2100 in response to climate change Number of coastal policies expected to increase by 130% 42

43 How is SLR currently treated in NFIP? Directly considered: BCA Calculations for HMA grants Indirectly considered: NFIP Contingency Loadings Long-term coastal erosion, a consequence of long-term SLR, is discussed in detail in FEMA s Coastal Construction manual Brief section in Coastal Construction Manual NFIP Community Rating System (CRS) now gives credit for community efforts to anticipate and take actions that can mitigate adverse impacts from climate change Insurance rates in V Zones consider generalized effects of long-term coastal erosion 43

44 FEMA and SLR FEMA Study on Projected Impact of RSLR on NFIP GAO instructed FEMA to analyze impacts of climate change on NFIP FEMA National CC Study 2008 NC Sea Level Rise Impact Study 2009 FEMA SLR Proof of Concept Study 2012 Biggert-Waters Flood Insurance Reform Act Ensure that FEMA uses best available climate science, sea level rise and future development information to access flood risk. Future implementation pending Technical Mapping Advisory Council SLR Proof of Concept/Pilot Studies PR, FL and CA 44

45 Biggert-Waters Flood Insurance Reform Act of 2012 Section : Authorizes FEMA to include sea level rise information in FIRM updates Inclusion of this information on FIRMs will be done in coordination with a Technical Mapping Advisory Council established in Section Section : Establishes TMAC (Technical Mapping Advisory Council) TMAC will be comprised of members from Federal, State, Local governments, as well as representatives from various Organizations and Associations TMAC will be charged in part in developing recommendations to FEMA on how to incorporate Climate Change data and information into the NFIP 45

46 SLR Advisory Layer Concept Non-regulatory (advisory) Low incremental production cost Develop as add-on to Risk MAP studies Leverage models/data produced by FIS Convey future changes to coastal flood hazard Guide long-term planning & adaptation Develop for pro-active states & communities 46

47 SLR Proof of Concept/Pilot Studies Study areas: Puerto Rico (Caribbean Sea) San Francisco County, CA (Pacific Ocean) Hillsborough and Pinellas Counties, FL (Gulf of Mexico) Goals: Work closely with coastal communities to produce SLR information for advisory purposes Further test whether linear super-position ( bathtub approach ) is adequate for NFIP flood-mapping purposes Test and refine approaches for modeling and mapping Counties selected because: Willingness to work with FEMA on SLR Test different coastal environments (different than PR and NC studies) Leverage ongoing coastal flood studies 47

48 Questions? Dewberry Jeff Gangai, CFM FEMA Robert Pierson