FLOOD HAZARD IN THE URBAN ENVIRONMENT: IMPLICATIONS FOR DEVELOPERS, DESIGNERS, AND ATTORNEYS

Transcription

1 FLOOD HAZARD IN THE URBAN ENVIRONMENT: IMPLICATIONS FOR DEVELOPERS, DESIGNERS, AND ATTORNEYS PRESENTED BY: CHAD W. COX, P.E. DANIEL C. STAPLETON, P.E. BOSTON, MA JAN. 24, 2014

2 PRESENTATION Flood Vulnerability - Boston FEMA - Flood Insurance Rate Maps Risk-Informed Decision-Making Property Development

3 Boston Flood Vulnerability It could happen here

4 Boston Flood Vulnerability Rt. 35 in the Ortley Beach section of Toms River on Oct. 31, 2012 two days after superstorm Sandy struck New Jersey (file photo by Doug Hood)

5 Boston Flood Vulnerability MARKO GEORGIEV/STAFF PHOTOGRAPHER

6 Boston Flood Vulnerability

7 Boston Flood Vulnerability

8 Boston Flood Vulnerability Credits: Timothy A Clary

9 Boston Flood Vulnerability: Flood Mechanisms Three Primary Flood Mechanisms: Local Intense Precipitation Riverine Flooding Coastal Flooding

10 Boston Flood Vulnerability: Flood Mechanisms A. Local Intense Precipitation Return Period 60 min. Precip. 1 yr yr yr yr yr yr yr yr yr. 4.43

11 Boston Flood Vulnerability: Flood Mechanisms B. Riverine Flooding Return Period 24 Hr. precip. 1 yr yr yr yr yr yr yr yr yr

12 Boston Flood Vulnerability: Flood Mechanisms C. Coastal Flooding Storm Surge Photo by Jeremy Fox in Boston Harbor Assoc. Report

13 Boston Flood Vulnerability: Flood Mechanisms C. Coastal Flooding Waves Ocean waves crash over a seawall and into houses along the coast in Scituate, Mass., Thursday, March 7, A nor'easter is bringing wind-whipped, wet snow to Massachusetts, and coastal flooding is expected in communities still recovering from February's blizzard. (AP Photo/Steven Senne)

14 Boston Flood Vulnerability: Storm Types Nor-Easters Top Ten Boston Flood Events No.1 Blizzard of 1978

15 Boston Flood Vulnerability: Storm Types Hurricanes

16 Boston Flood Vulnerability: Coastal Flooding Storm Surge and Waves GEOGRAPHICAL FACTORS STORM FACTORS

17 Property Development FEMA INSURANCE STUDIES FLOOD MAPS

18 FEMA Flood Insurance Rate Maps Federal Emergency Management Agency NFIP = National Flood Insurance Program FIRM = Flood Insurance Rate Map FIS = Flood Insurance Study BFE = Base Flood Elevation

19 FEMA Flood Insurance Rate Maps: Base Flood Elevation BFE Base Flood Elevation The computed elevation to which floodwater is anticipated to rise during the base flood. Base Flood Elevations (BFEs) are shown on Flood Insurance Rate Maps (FIRMs) and on the flood profiles.the BFE is the regulatory requirement for the elevation or floodproofing of structures. The relationship between the BFE and a structure's elevation determines the flood insurance premium.

20 FEMA Flood Insurance Rate Maps: Special Flood Hazard Area SFHA Special Flood Hazard Area The land area covered by the floodwaters of the base flood is the Special Flood Hazard Area (SFHA) on NFIP maps. The SFHA is the area where the National Flood Insurance Program's (NFIP's) floodplain management regulations must be enforced and the area where the mandatory purchase of flood insurance applies. Special Flood Hazard Areas are divided into various Zones

21 FEMA Flood Insurance Rate Maps: Zone AE Zone A, AE, Coastal AE Areas subject to inundation by the 1-percent-annualchance flood event determined by detailed methods. Base Flood Elevations (BFEs) are shown. Mandatory flood insurance purchase requirements and floodplain management standards apply.

22 FEMA Flood Insurance Rate Maps: Coastal High Velocity Zones Zone V, VE Areas subject to inundation by the 1-percent-annualchance flood event with additional hazards due to storminduced velocity wave action. Base Flood Elevations (BFEs) derived from detailed hydraulic analyses are shown. Mandatory flood insurance purchase requirements and floodplain management standards apply..

23 FEMA Flood Insurance Rate Maps Courtesy of FEMA

24 FEMA Flood Insurance Rate Maps Wave Action (VE, AE) Surge Inundation (AE) This photo provided by 6abc Action News

25 FEMA Flood Insurance Rate Maps

26 FEMA Flood Insurance Rate Maps Flood Hazards 2009 Preliminary Flood Hazards SOURCE: Federal Emergency Management Agen

27 FEMA Flood Insurance Rate Maps: Current FEMA FIRM South Boston Seaport District

28 FEMA Flood Insurance Rate Maps: Preliminary FEMA FIRM South Boston Seaport District

29 FEMA Flood Insurance Rate Maps SOME IMPORTANT DETAILS! Previous FIS: The Preliminary Maps are not yet final and are subject to appeal.

30 Risk-Informed Decision-Making: Understanding Flood Risk Flood Risk = Hazard Probability x Consequence The flood hazard(s) leading to the site flood impact (i.e., adverse outcome). The likelihood(s) (probability) of the flood hazard(s) occurring. The performance of the structure during the flood event (i.e. probability of failure). The consequence(s) (qualitative or quantitative of the site flood impact; e.g., damage, business losses, loss of life, etc.) of the scenario occurring.

31 Risk-Informed Decision-Making: Understanding Flood Risk Ref. FEMA

32 Risk-Informed Decision-Making: Understanding Flood Risk

33 Risk-Informed Decision-Making: Understanding Flood Risk 100-YR 1,000-YR

34 Risk-Informed Decision-Making: Understanding Flood Risk Estimated Superstorm Sandy Return Period for Manhattan Approx. 300 to 500Years Credits: Timothy A Clary

35 Risk-Informed Decision-Making: Determining Flood Hazard Stillwater Elevation - Tide Gage Data Stillwater Elevation (feet, NAVD88) Observed Annual Max Calculated Stage-Frequency Curve - GEV Fit Boston - Preliminary FIS Nov Return Period (Years) NOAA Co-op Tide Gage, Boston Harbor, Massachusetts (Station )

36 Risk-Informed Decision-Making: Determining Flood Hazard STILLWATER ELEVATION - STORM SIMULATION HURRICANE PARAMETERS Central Pressure Peripheral Pressure Radius of Maximum Winds Track Direction Forward Translational Speed

37 Risk-Informed Decision-Making: Determining Flood Hazard HURDAT Database Synthetic Storms (Atmospheric Models)

38 Risk-Informed Decision-Making: Determining Flood Hazard NOAA SLOSH Storm Surge Model Computationally efficient simulate thousands of synthetic storms Reference: GZA Hydraulic & Hydrology Modeling Services

39 Risk-Informed Decision-Making: Determining Flood Hazard AdCIRC Model Sandy simulation Reference: GZA Hydraulic & Hydrology Modeling Services

40 Risk-Informed Decision-Making: Determining Flood Hazard AdCIRC Model Wind Field for Sandy Reference: GZA Hydraulic & Hydrology Modeling Services

41 Risk-Informed Decision-Making: Determining Flood Hazard WIND-GENERATED WAVES Wave Height Wave Period Deepwater Nearshore Refraction Wave Runup Overtopping

42 Risk-Informed Decision-Making: Determining Flood Hazard Wind and Wave Buoy Data UASCE WIS Data

43 Risk-Informed Decision-Making: Determining Flood Hazard SWAN2D WAVE MODEL Reference: GZA Hydraulic & Hydrology Modeling Services

44 Risk-Informed Decision-Making: Determining Flood Hazard Overland Inundation WHAFIS 1D MODEL Reference: GZA Hydraulic & Hydrology Modeling Services

45 Risk-Informed Decision-Making: Determining Flood Hazard TWO-DIMENSIONAL FLOOD INUNDATION MODELING Reference: GZA Hydraulic & Hydrology Modeling Services

46 Property Development PROPERTY DEVELOPMENT SITE SELECTION BUILDING CODE PERMITTING RISK STRATEGY

47 Property Development: Siting Considerations GZA Phase I and II Flood Vulnerability Assessments: Flood Hazard Design Flood Elevation Existing Site Grades Floodway Encroachment Scour and Erosion Potential Shoreline and Waterfront Structures Utilities Permit and Code Requirements Site Plan Flood hazard areas Floodways Design Flood Elevations

48 Property Development: Building Code Requirements/Local Ordnances How Flood Regulations Influence Buildings NFIP Regulations, 44 Part 60 Floodplain Management Ordinance (varies by community) Building Building Codes IBC NFPA 5000 Consensus Standards ASCE 7 (Minimum Design Loads for Buildings and Other Structures) ASCE24 (Flood Resistant Design and Construction) Source: WBDG

49 Property Development: Building Code Requirements Building Code: IBC: Chapters: 1 - Administration 11 - Accessibility 14 - Exterior Walls 16 Structural Design 18 Soils and Foundations Highlights: Land Use Regulations and Codes NFIP Facility Category (ASCE 7) Load Combinations (ASCE 7) Siting Considerations (ASCE 24) Freeboard (ASCE 24) Fill (ASCE 24) Foundations (ASCE 24) Erosion and Scour (ASCE 24)

50 Property Development: Building Code Requirements Section 1612 Flood Loads:

51 Property Development : NFIP/Building Code Requirements GZA Flood Vulnerability Assessment Code Crosswalk Table:

52 Property Development : Permitting Federal Clean Water Act MA Chapter 91 MA Wetlands Protection Act Local Flood Plain Ordinance Local Wetlands Ordinance (Future Boston intended to explicitly account for sea level rise) Zoning (BOSTON - Article 80 Review)

53 Property Development : Permitting Article 80 Review Guidelines Appendix 7 (addition of a new section) Climate Change Resiliency and Preparedness Checklist

54 Property Development Issues: Permitting What Extreme Rain Event characteristics will be used for project planning Seasonal Rain Fall, Peak Rain Fall, and Frequency of Events per year? Inches / yr. Inches Events / yr. Sea-Level Rise and Storms Rising Sea-Levels and more frequent Extreme Storms increase the probability of coastal and river flooding and enlarging the extent of the 100 Year Flood Plain. This section explores if a project is or might be subject to Sea-Level Rise and Storm impacts. Location Description and Classification: Do you believe the building to susceptible to flooding now or in the full expected life of the building? Yes / No

55 Property Development Issues: Permitting Sea-Level Rise and Storms This section explores how a project responds to Sea-Level Rise and / or increase in storm frequency or severity. Analysis How were impacts from higher sea levels and more frequent and extreme storm events analyzed: Sea Level Rise: Ft. Frequency of storms: per year Building Flood Proofing Describe any strategies to limit storm and flood damage and to maintain functionality during extended periods of disruption. Has ground floor level been elevated in response to Sea Level Rise: First Floor Elevation: Boston City Base Elev.( Ft.) Height above 100 Year Floodplain: Boston City Base Elev. ( Ft.)

56 Property Development Issues: Permitting Building Resilience and Adaptability Describe any strategies that would support rapid recovery after a weather event and accommodate future building changes that respond to climate change: Will the building be able to withstand severe storm impacts and endure temporary inundation? Select appropriate: Yes / No Hardened / Resilient Ground Floor Construction, Temporary shutters and or barricades, Resilient site design, materials and construction

57 Climate Change Implications CLIMATE CHANGE MORE INTENSE STORMS SEA LEVEL RISE

58 Climate Change Implications: Global Changes Source: Intergovernmental Panel on Climate Change

59 Climate Change Implications: Increased Precipitation Intensity

60 Climate Change Implications: Increased Storm Intensity

61 Climate Change Implications: Increased Storm Intensity Source: Aslak Grinsted, John C. Moore, Jretiana Jevrejeva

62 Climate Change Implications: Sea Level Rise

63 Climate Change Implications: Sea Level Rise Source: CCSR,

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67 Climate Change Implications: Net Effect Increased Flooding and Flood Frequency Climate Change FEMA Base Flood Elevation Reference: GZA Hydraulic & Hydrology Modeling Services

68 Property Development Issues: Sea Level Rise 50 yrs Sea Level Rise ONLY High Moderate Low Source: CCSR, 2011

69 Risk Strategy MITIGATION RISK STRATEGY INSURANCE RESIDUAL RISK

70 Risk Strategy: Mitigation Architect: Perkins + Will Analytical diagrams P+W / Partners HealthCare

71 1. NFIP Risk Strategy: Insurance The Biggert-Waters Flood Insurance Reform Act of 2012 (BW-12) In July 2012, the US Congress passed the Biggert-Waters Flood Insurance Reform Act of 2012 (BW-12) which requires the NFIP to raise rates to reflect true flood risk, make the program more financially stable, and change how Flood Insurance Rate Map (FIRM) updates impact policyholders. Flood Insurance Reform Act of Comprehensive (Commercial) Coverage

72 Risk Strategy: Insurance Source: FEMA

73 Risk Strategy : Manage Residual Risk Emergency Response Plan Evacuation Plans Operations Personnel Pre-Positioned in Safe Area Auxiliary Power Supply Tested, Fueled, and Above Flood Level Emergency Communications Systems Data Backup Potential Environmental Issues Secured Contractor On-Call Employee / Tenant Communications Plan in Place

74 Risk Strategy How Goldman Sachs protects itself from a hundred-year storm -Reuters $1,000,000! (Picture from Stephen Foley) Source: Stephen Foley

75 FLOOD HAZARD IN THE URBAN ENVIRONMENT: IMPLICATIONS FOR DEVELOPERS, DESIGNERS, AND ATTORNEYS Mary Hall, P.E. Bruce Fairless, P.E. Chad Cox, P.E. Dan Stapleton, P.E. BOSTON, MA JAN. 24, 2014