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
Outline Where Why What How Input Conditions Methodology Products Regulatory Non-Regulatory Outreach
Where
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
Why NAS Develops Wave Analysis Methodology NFIP Authorized 1973 1979 Runup Methodology Accepted 1986 to 1988 PFD 1989 G&S for Wave Elevation and V Zone Mapping Proc. Memo No. 37 2002 Proc. Memo No. 50 2007 1968 1977 1981 1988 1995 2005 2008 H b = 3' FEMA Adopts NAS Methodology Wetland Vegetation Muddy Bottom Erosion Analysis (540SF) CERC TR 89-15 Appendix D Atlantic Ocean and Gulf of Mexico Guidelines Update (Final Draft)
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
How Detailed coastal analysis Stillwater Level Overland Wave Propagation Wave Runup and Overtopping Primary Frontal Dune
Stillwater Elevations Return period gage analysis Linear interpolation between gage points
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
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
Wave Setup
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
Coastal Structures Intact Profile Use the existing conditions for topographic detail Failed Profile Use guidance in 89-15 and Guides and Specs to fail the structure
Field Reconnaissance
Field Survey
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
Flood Insurance Rate Maps / Flood Insurance Study
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
Changes Since Last FIRM SFHA Decrease SFHA Increase
Wave Height Grids Provided for 1% annual chance floods
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
Countywide Changes Since Last FIRM County Area of Change Total Area [mi 2 ] Net Area Change [mi 2 ] Approximate Population Fairfield SFHA 80.92 2.11 7,103 2,006 Velocity 15.10 2.88 1,561 469 Middlesex SFHA 50.79 0.84 1,258 Velocity 5.94 1.71 585 New Haven SFHA 71.53 1.22 3,996 Velocity 13.73 1.93 550 New London SFHA 84.02 1.25 1,237 Velocity 21.00 2.93 747 Approximate Buildings
Countywide Changes Since Last FIRM County Area of Change Total Area [mi 2 ] Net Area Change [mi 2 ] Approximate Population Fairfield SFHA 80.92 2.11 7,103 2,006 Velocity 15.10 2.88 1,561 469 Middlesex SFHA 50.79 0.84 1,258 Velocity 5.94 1.71 585 New Haven SFHA 71.53 1.22 3,996 Velocity 13.73 1.93 550 New London SFHA 84.02 1.25 1,237 Velocity 21.00 2.93 747 Connecticut SFHA 287.26 5.42 13,594 Velocity 55.47 9.45 3,443 Approximate Buildings
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
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
Surveyed Salt Burn
Zoomed In
Salt Burn versus 1-percent-annual-chance Flood
Map Effective Dates County Middlesex New Haven Fairfield New London Effective Date 6-FEB-2013 8-JUL-2013 8-JUL-2013 5-AUG-2013