Physical Map Revisions in Connecticut due to Updated Coastal Flood Hazards F8: Maps in Transition

Transcription

1 Physical Map Revisions in Connecticut due to Updated Coastal Flood Hazards F8: Maps in Transition Brian Caufield, P.E., CFM Principal Engineer CDM Smith Kerry Bogdan, CFM Senior Engineer FEMA Region I Thursday, June 13, 2013

2 Outline Where Why What How Input Conditions Methodology Products Regulatory Non-Regulatory Outreach

3 Where

4 Specifics FEMA funded coastal Physical Map Revisions in FY09 4 Counties (Fairfield, New Haven, Middlesex, New London) 27 Communities 168 FIRM Panels 218 Shoreline Miles yesteryearremembered.com

5 Why NAS Develops Wave Analysis Methodology NFIP Authorized Runup Methodology Accepted 1986 to 1988 PFD 1989 G&S for Wave Elevation and V Zone Mapping Proc. Memo No Proc. Memo No H b = 3' FEMA Adopts NAS Methodology Wetland Vegetation Muddy Bottom Erosion Analysis (540SF) CERC TR Appendix D Atlantic Ocean and Gulf of Mexico Guidelines Update (Final Draft)

6 Study Timeline Discovery Meeting May 5, 2010 Work Map Meetings June 8, 2011 Preliminary November 15, 2011 CCO Meeting January 17, 2011 Projected Effective February 2013 Projected LFD August 2012

7 How Detailed coastal analysis Stillwater Level Overland Wave Propagation Wave Runup and Overtopping Primary Frontal Dune

8 Stillwater Elevations Return period gage analysis Linear interpolation between gage points

9 Wave Heights Open water settings Use a return period analysis of wind data to define 1- percent-annual-chance wind speed Wind speed used to define the input wave height Restricted fetch setting Account for directional approach in restricted settings Wind speed used to define the input wave height

10 Topographic Data 2-foot contour data Contours generated from 2 LiDAR missions Connecticut River LiDAR Mission flown in 2004 Coastal LiDAR mission flown in 2007

11 Wave Setup

12 Wave Runup Effective studies used the Average value from the wave runup computation New guidance is to use the 2% value Important for steep slope areas Factor of 2.2 increase from effective studies to new studies Effective study wave runup of 10 feet above SWEL Translate to 22 feet above SWEL

13 Coastal Structures Intact Profile Use the existing conditions for topographic detail Failed Profile Use guidance in and Guides and Specs to fail the structure

14 Field Reconnaissance

15 Field Survey

16 Work Map Meeting One hour with each community Effective FIRM basemap Highlighted: V/A Boundary Primary Frontal Dune Limit of 1% Limit of 0.2% Limit of Moderate Wave Action Limit of Study

17 Flood Insurance Rate Maps / Flood Insurance Study

18 Limit of Moderate Wave Action Areas subject to wave heights greater than 1.5 feet Coastal A Zone Recommendation of building to V zone standards Currently non-regulatory in Connecticut

19 Changes Since Last FIRM SFHA Decrease SFHA Increase

20 Wave Height Grids Provided for 1% annual chance floods

21 Contributing Engineering Factors Provide insight into the factors behind the increase or decrease in the flood hazard areas Can prove to be useful for planning and mitigation measures

22 Countywide Changes Since Last FIRM County Area of Change Total Area [mi 2 ] Net Area Change [mi 2 ] Approximate Population Fairfield SFHA ,103 2,006 Velocity , Middlesex SFHA ,258 Velocity New Haven SFHA ,996 Velocity New London SFHA ,237 Velocity Approximate Buildings

23 Countywide Changes Since Last FIRM County Area of Change Total Area [mi 2 ] Net Area Change [mi 2 ] Approximate Population Fairfield SFHA ,103 2,006 Velocity , Middlesex SFHA ,258 Velocity New Haven SFHA ,996 Velocity New London SFHA ,237 Velocity Connecticut SFHA ,594 Velocity ,443 Approximate Buildings

24 Resilience Combination of Mitigation Planning and Insurance Looked for regional groupings to maximize participation Looked for unique opportunities City of Milford s 2012 Oyster Festival

25 Community Acceptance City of Milford Performed High Water Mark surveys post Irene & Sandy Town of Old Saybrook Adopted Coastal A Zone language into Building Ordinance Additional communities evaluating adopting Coastal A Zone language Maps hard to read FEMA Region I creating Coastal A Zone polygons from FIRM database

26 Surveyed Salt Burn

27 Zoomed In

28 Salt Burn versus 1-percent-annual-chance Flood

29 Map Effective Dates County Middlesex New Haven Fairfield New London Effective Date 6-FEB JUL JUL AUG-2013

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