Storm Surge Analysis Update Meeting Hillsborough and Manatee Counties April 5, 2016

Transcription

1 West Florida Coastal Storm Surge Study Storm Surge Analysis Update Meeting Hillsborough and Manatee Counties April 5, 2016

2 Agenda Introductions Goals for Today West Florida Coastal Surge Study Project Overview & Schedule Storm Surge Methodology Stillwater Elevation Information Risk MAP Overview & Products Mitigation Actions Next steps Meet to gather input Anclote Power Plant Bayshore Boulevard Hickory Mound Unit 2

3 Introductions Risk MAP Project Team FEMA Region IV Southwest Florida Water Management District (SWFWMD) RAMPP staff (study contractor) Horseshoe Beach 3

4 Who s Here? State partners and officials Officials from local communities Floodplain Administrators Emergency Managers Engineers FEMA contracted engineering firms Federal agency partner representatives Non-governmental organizations 4

5 Goals for Today Promote engagement with the communities Discuss the West Florida Coastal Surge Study and the status of the study Discuss the study methodology and results Mesh Development Storm Climatology Validation Storms Stillwater Elevations Gather technical inputs and feedback from you 5

6 Your Role is Important Share local data or new information Identify potential issues Provide feedback on coastal study interim results Relate study information and status to other stakeholders Concerned stakeholder Shell Mound County Park 6

7 FEMA Region IV Coastal Studies 7

8 West Florida Coastal Surge Study 8

9 Project Work Plan Work to be done by RAMPP (PTS): Perform coastal storm surge and wave height analyses for Citrus, Hernando, Pasco, Pinellas, Hillsborough, and Manatee Counties Perform coastal floodplain delineation and develop workmaps Develop coastal Risk MAP Products Support Discovery and Outreach to create ownership of the coastal analysis at state and local level Work to be done by BakerAECOM (PTS): Perform the preliminary map production Perform post-preliminary map production and CCO/Open House Meeting CCO: Consultation Coordination Officer PTS: Production Technical Services 9

10 Why Update Surge in West Florida Flood risk changes over time Effective study based on an outdated hurricane modeling and topographic data We chose your counties to review due to risk and ongoing studies in the area Significant flood risk from coastal storms (hurricanes, tropical storms, nor'easters) Increase in population and development since effective coastal FIRMs were published Ongoing riverine watershed flood studies To gain a complete and current picture of coastal flood risks. This helps the community: Plan for the risk Communicate the risk to your citizens Take action to reduce flood risk to lives and property Build smarter and safer 10

11 Why Update Surge in West Florida Current surge analysis is 33 years old Citrus: 1984 (HUD Standard Storm Surge Model) Hernando: 1984 (HUD Standard Storm Surge Model) Pasco: 1981 (FIA Standard Storm Surge Model) Pinellas: 1981 (FEMA Standard Storm Surge Model) Hillsborough: 1984 (FEMA Standard Storm Surge Model) Manatee: 1992 (FEMA Standard Storm Surge Model) 11

12 Why Update Surge in West Florida Your risk is better defined through Implementation of new guidelines Atlantic Ocean and Gulf of Mexico Guidelines Update (2007) Sheltered Water Report (2008) PM 50 Limit of Moderate Wave Action (LiMWA) (2008) Base data updated: topographic dataset and aerial imagery to high resolution products and seamless Digital Elevation Model (DEM) New climatological data based on recent storms Updated coastal hazard methodologies/modeling Improvement in GIS technologies to improve coastal mapping accuracy 12

13 Why Update Surge in West Florida FDEM Evacuation Study 2010 study to map inundation levels for evacuation planning Project area includes all of Florida coast Base data includes recent LiDAR data Uses SLOSH model West Florida Coastal Study Study to map 1% annual chance flood hazard area Project includes West FL counties only Base data includes recent LiDAR data Uses ADCIRC and SWAN Models Source: 13

14 Storm Surge Approach High-Resolution Bathy / Topo Mesh Storm Surge Modeling Waves Winds Return Period Analysis JPM-OS 10%, 4%, 2%, 1%, & 0.2% annual chance Tide Gage Analysis 50% & 20% annual chance Still Water Elev. Water Levels Storm Forcing -Extratropical Wind Fields - Hurricane Tracks Surge (m) jpm 6 stochastic 4 8 jpm stochastic jpm Return 6 Period stochastic (years) Surge (m) Surge (m) Return Period (years) Return Period (years) JPM-OS: Joint Probability Method- Optimum Sampling 14

15 Development of ADCIRC Mesh ADCIRC: ADvanced CIRCulation Model Finite element difference model Uses unstructured, triangulated mesh Node spacing set to accurately represent underlying topography/bathymetry Created feature arcs to represent elevated features (i.e. roads) 15

16 Development of ADCIRC Mesh Feature Arcs 16

17 Development of ADCIRC Mesh ADCIRC Mesh 17

18 West Florida Draft Results - Mesh MacDill Air Force Base, Tampa 18

19 West Florida Draft Results - Mesh MacDill Air Force Base, Tampa 19

20 West Florida Draft Results - Mesh Alafia River 20

21 West Florida Draft Results - Mesh Alafia River 21

22 West Florida Draft Results - Mesh Little Manatee River 22

23 West Florida Draft Results - Mesh Little Manatee River 23

24 West Florida Draft Results - Mesh Entrance to Manatee River, Terra Ceia Bay 24

25 West Florida Draft Results - Mesh Entrance to Manatee River, Terra Ceia Bay 25

26 West Florida Draft Results - Mesh Palma Sola Bay 26

27 West Florida Draft Results - Mesh Palma Sola Bay 27

28 Current surge analysis is 33 years old Citrus: 1984 (HUD Standard Storm Surge Model) Hernando: 1984 (HUD Standard Storm Surge Model) Pasco: 1981 (FIA Standard Storm Surge Model) Pinellas: 1981 (FEMA Standard Storm Surge Model) Hillsborough: 1984 (FEMA Standard Storm Surge Model) Manatee: 1992 (FEMA Standard Storm Surge Model) 28

29 FEMA Standard Surge Model vs ADCIRC SWFL ADCIRC mesh. Spacing 90 to 300 feet. FEMA Standard Surge Model. Cells are 1500 feet x 1500 feet 29

30 Storm Climatology Tropical Storms The quiet corner of the Gulf: Typically Category 1 or less at landfall Tropical Storms: Tropical Storms:

31 Storm Climatology Extra-Tropical: Intense storms can develop in the Gulf before crossing Florida and racing up the East Coast as a Nor easter 52-knot wind speed maxima analyzed during March 1993 Super Storm 31

32 Storm Climatology Storm events were determined using NOSmeasured hourly water level data from eight measurement stations. Period from 1965 to 2012 was considered. NOS: National Ocean Service 32

33 Event Name Date Surge at St. Petersburg, FL (NAVD88 feet) Great Gale of /25/ Tampa Bay Hurricane 10/25/ Labor Day Hurricane 9/4/1935 Hurricane Easy 9/5/ Hurricane Brenda 7/29/ Hurricane Alma 6/9/ Hurricane Gladys 10/19/ Hurricane Agnes 6/19/ Subtropical Storm One 6/25/ Subtropical Storm One 6/18/ Hurricane Elena 8/31/ Hurricane Juan 11/1/ March '93 Super Storm 3/13/ Hurricane Opal 10/4/ Tropical Storm Josephine 10/8/ Hurricane Gordon 9/17/ Hurricane Frances 9/6/ December '04 extra-tropical 12/26/ Hurricane Dennis 7/10/

34 Validation Storm Selection Validation storms Tropical Storms Tropical Storm Josephine (1996) Hurricane Frances (2004) Hurricane Dennis (2005) Extra-tropical Storms March 1993 (Storm of the Century) 34

35 Synthetic Storms Define synthetic storms using six parameters Central pressure, Radius to maximum winds, Forward speed, Storm heading, Holland s B (shape parameter), and landfall location Ensure covers whole range of possible storms for West FL Based on historic data for the area Total of 600+ synthetic storms were developed for West FL 35

36 Completed Work Summary Set up mesh for hurricane/surge model Validated hurricane/surge model Ran hundreds of synthetic storms Computed return periods for study area (0.2%, 1%, 2%, 4%, 10%, 20%, 50% - annual chance) Resulting storm surge stillwater elevations for the 1% annual chance event 36

37 West FL Stillwater Elevation Results Calculated 1-percent-annual-chance stillwater elevations (SWEL) These are intended to give you an idea of the results we are seeing Does not correlate directly to what FIRM may show because the published SWEL does include wave heights Results are variable throughout study area 37

38 Hillsborough County Stillwater Results 38

39 Hillsborough County Stillwater Results 39

40 Manatee County Stillwater Results 40

41 Manatee County Stillwater Results 41

42 Upcoming Work Overland Wave Modeling Mapping of Special Flood Hazard Areas (VE and AE zones), Base Flood Elevations (BFEs), Limit of Moderate Wave Action (LiMWA) Develop draft work maps and present at Flood Risk Review Meeting Develop Risk MAP non-regulatory products and present at Resilience Meeting 42

43 Basic Elements of a Coastal Study Base Flood Elevation (BFE) on a FIRM includes 4 components: Storm surge stillwater elevation (SWEL) Wave setup Determined from storm surge model Wave height above total stillwater elevation Wave runup above storm surge elevation (where present) All applied to an eroded beach profile (when applicable) The above components are computed through Terrain processing and profile erosion Storm surge study for SWELs determination Coastal Hazard Analysis 43

44 Basic Elements of a Coastal Study 44

45 Limit of Moderate Wave Action (LiMWA) FEMA Procedure Memorandum No. 50, 2008 & Operating Guidance 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 than 1.5 feet 45

46 Primary Frontal Dune (PFD) 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 NFIP regulations 46

47 Risk Map Program Overview FEMA works with communities to develop flood risk products and flood hazard maps that are: Based on the best available data from the community and latest technologies Conducted by watershed (Riverine) Conducted by affected communities and counties (Coastal) Strengthened by partnerships You can use Risk MAP tools and data to: Create or improve your Local Mitigation Strategies Make informed decisions about development, ordinances, and flood mitigation projects Communicate with citizens about flood risk 47

48 Program Product Comparisons Regulatory Products Non-Regulatory Products DFIRM Database Traditional products are regulatory and subject to statutory due-process requirements Risk MAP products are nonregulatory and are not subject to statutory due-process requirements 48

49 Flood Risk Map Visually Promotes Risk Awareness Contains results of Risk MAP project non-regulatory datasets Promotes additional flood risk data not shown but located within the Flood Risk Database 49

50 Changes Since Last FIRM Makes it easy for communities and homeowners to identify impacts of new FIRM Assists in prioritizing mitigation actions Helps identify reasons for changes 50

51 Mitigation Actions Local activities you could take to address flood risk Building Code Enforcement Enhanced Building Code Post Disaster Code Enforcement Community Identified Program CRS Land Use Ordinance Coastal Zone Management Open Space Preservation Stormwater Management Zoning Mitigation Projects Acquisition Elevation Erosion Control Retrofit Management Best Practices Integrate Natural Hazards into Planning Mechanisms 51

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53 Projected Schedule Flood Risk Review: Spring 2017 Resilience Meeting: Summer

54 Next Steps Questions & Answers We can meet you at the back of the room and capture your input Within two weeks, we would like from you: Feedback and comments Based on today s discussion, we will finalize and forward to you: Meeting Minutes & PowerPoint 54

55 Thank you We look forward to continuing to work with you to help the West Florida coastal area become more resilient to flooding. 55

56 Supplemental Resources Resource Community Rating System Fact Sheet FloodSmart.gov Website Fact Sheet HMA Grant Programs Fact Sheet Hazard Mitigation Assistance Unified Guidance Mitigation Planning Fact Sheet Mitigation s Value to Society Fact Sheet Region IV Mapping Analysis and Web Portal Fact Sheet Risk MAP and the NFIP: Answers to Frequently Asked Questions Risk MAP Flood Risk Products Fact Sheet Website act%20sheet_southeastunited%20states_eng pdf Acronyms: HMA = Hazard Mitigation Assistance, NFIP = National Flood Insurance Program, Risk MAP = Mapping, Assessment, and Planning 56

57 Questions Contact Information Mark Vieira Christina Lindemer Kevin Slover Emily Dhingra

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