1. Joseph L. DiLorenzo, Ph.D. NAJARIAN ASSOCIATES
COASTAL STORM CHARACTERISTICS AND CHANGES IN FLOOD INSURANCE RATE MAPS FOR COASTAL MONMOUTH COUNTY
Presented by:
Joseph L. DiLorenzo, Ph.D. NAJARIAN ASSOCIATES

2. OVERVIEW OF PRESENTATION
Characteristics of coastal storms in New Jersey
Changes in new FEMA Flood Insurance Rate Maps (FIRMs) for Monmouth County
Map accuracy
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3. TWO TYPES OF COASTAL STORMS Extra-tropical storms (Nor’easters)
Tropical cyclones
(hurricanes)
Extra-tropical storms (Nor’easters)
No central eye
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4. TROPICAL CYCLONES (HURRICANES)
warm-core systems that derive energy from oceanic evaporation
cause intense, short-duration surges and wind
potential catastrophic damages, but somewhat localized
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5. HURRICANE TRACKS (SINCE 1850)
Most hurricanes skirt NJ and weaken
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6. HURRICANE DONNA September 12, 1960 at Sandy Hook
MSL
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7. MONMOUTH COUNTY INUNDATION ZONES
Category 1 & 2 hurricanes since 1850
On Sept. 3, 1821, a Category 4 hurricane passed over LBI

8. EXTRATROPICAL STORMS (NOR’EASTERS)
cold-core cyclonic systems
formed in areas where strong surface temperature gradients coincide with a strong jet stream aloft
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9. EXTRATROPICAL STORMS – NOR’EASTERS
Cause prolonged flooding when blocked by presence of high pressure systems in northeast Canada
large scale systems – can flood and erode east coast regions
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10. HISTORIC NOR’EASTER December 11, 1992 at Sandy Hook
MSL

11. TIDAL DATUMS AT SANDY HOOK
Mean High Water
North American Vertical Datum of 1988
Mean Sea Level
1.09 ft
0.86 ft
Sea level Datum of 1929
Mean Lower Low Water
(Source: NOAA)
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12. 1992 NOR’EASTER – NOAA SITES
Maximum Stillwater Elevations
Highest observed water level over ~100 year record
(January present)
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13. JOLINE AVENUE, LONG BRANCH DEC. 11, 1992
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14. 1992 NOR’EASTER – USGS SITES
Amplification at head of funnel-shaped Raritan Bay
Like Atlantic City maximum elevation (7.35 ft)
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15. COASTAL FLOOD RANKINGS
Top Eight Coastal Storms at Sandy Hook (1910-present; Source: NOAA)
RANK
DATE
STILL-WATER ELEVATION (FT, NGVD-1929) 1
12/11/92
8.69 2
9/12/60
8.37 3
11/12/68
7.09 4
1/23/66
7.06 5
3/29/84
6.95 6
3/14/93
6.94 7
1/02/87
6.91 8
9/27/85
6.86
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16. FEMA’s BASE FLOOD
The flood event having a probability of 0.01 (1%) of being equaled or exceeded in any given year
Commonly called the “100-year flood” (on average)
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17. BASE FLOOD ELEVATION (BFE)
The corresponding water surface elevation of the 1% annual chance flood (100-year flood)
Often determined by numerical modeling of coastal hydrodynamic processes
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18. BASE FLOOD ELEVATION (BFE) IN NO WAVE ZONES
Community
100-Year Stillwater
Elevation (ft)
NGVD NAVD88
Highlands
10.8
9.7
Atlantic Highlands
11.6
10.5
Middletown
Keansburg
Union Beach
11.8
10.7
Keyport
Sea Bright 9
7.9
Monmouth Beach
10.1
9.0
Long Branch
8.6
7.5
Neptune
8.5
7.4
Asbury Park
Avon
Belmar
Spring Lake
Manasquan
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19. BASE FLOOD ELEVATION (BFE) IN AREAS AFFECTED BY WAVES
Combines 100-year stillwater elevation, 100-year wave crest elevation and inland extent of wave runup
BFEs used to delineate Flood Hazard Areas inundated by 100-year storms on Flood Insurance Rate Maps (FIRMs)
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20. NEW FLOOD INSURANCE RATE MAPS (FIRMS)
New FIRMS delineate Flood Hazard Areas inundated by 100-year flood with blue dot shading
BFEs labeled (in feet, NAVD-1988) in Zone AE (e.g., EL11)
Areas inundated by 500-year flood (0.2% chance flood) are shaded with black dots
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21. KEY QUESTIONS Najarian Associates
Are delineated flood hazard areas significantly different from previous maps for coastal Monmouth County?
What are the reasons for the changes?
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22. CHANGES IN THE NEW FIRMS FOR MONMOUTH COUNTY
Some changes are due to re-delineations of flood hazard areas based on updated topographic data
Major changes along Bayshore are due to new FEMA standards for dunes and flood control structures
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23. RE-DELINEATION OF FLOOD HAZARD AREAS
New maps re-delineate 100-year floodplain boundary using the SAME BFEs but with updated Monmouth County topography (2 foot contours)
Community
Previous stillwater
elevation (ft)
NGVD NAVD88
New stillwater
NGVD29 NAVD88
Highlands
10.8
9.7
Atlantic Highlands
11.6
10.5
Middletown
Keansburg
Union Beach
11.8
10.7
Keyport
Sea Bright 9
7.9
Monmouth Beach
10.1
9.0
Long Branch
8.6
7.5
Neptune
8.5
7.4
Asbury Park
Avon
Belmar
Spring Lake
Manasquan
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24. MINOR CHANGES IN MOST COASTAL AREAS
Example of minor re-delineation of 100-year (1%) flood lines due to use of updated topography
Old: Yellow Line
New: Blue Line
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25. MAJOR CHANGES ALONG BAYSHORE
Massively expanded flood hazard area due to more stringent FEMA standards for protective dunes/levees
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26. PROJECT HISTORY Najarian Associates
: Keansburg area project constructed Dune and levees built 15 ft high based on highest storm to date
Early 1980s: FEMA provisionally approves 14,700 foot long “levee,” with minimum flood insurance burden to residents
Over time, dune thickness decreased significantly - area vulnerable
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27. PROJECT HISTORY Najarian Associates
: Army Corps plans repairs
Beach renourishment proposed
Use same 15 ft dune crest elevation (not 18 ft BFE)
Benefit/Cost >1 Keansburg, Port Monmouth & Union Beach
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28. PROJECT HISTORY Najarian Associates
2007: FEMA revises standards (44 CFR )
No longer considers the “levee” a levee or a protective dune
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29. LEVEE STANDARD Najarian Associates 44 CFR §65.10 In this case:
Must be non-eroding structure during the 100-year storm
Must be 1 ft above 100-year storm wave height (i.e., no wave over-topping)
In this case:
“Structure” erodes
About 40% of “structure” below required height
17.7 ft NAVD (10.5 ft ft+ 1 ft)
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30. DUNE STANDARD Najarian Associates 44 CFR §65.11 (Dune standards)
Cross-sectional area must exceed 540 sq. ft and have vegetative cover
(seaward of dune crest and above 100-year SWE of 10.5 ft NAVD-1988)
In this case:
Bayshore dune cross-section too small (<70 sq. ft.)
FEMA still giving credit by eliminating V-zone behind dune
BFE 11 ft behind dune, essentially same as 100-year SWE
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31. PRESENT DILEMMA Najarian Associates
U.S. Army Corps shelved previous (non-compliant) dune repair plans which would not eliminate flood insurance burden
Compliant new plans will not satisfy benefit-to-cost criteria
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32. ISSUE: AGENCY DISCONNECT IN INITIAL DESIGN LEVEL
ARMY CORPS: whichever design level provides maximum net benefits to the government (may be as low as a 5-yr level with 50% assurance)
FEMA: 100-yr design with 95% assurance
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33. BIGGER DISCONNECT IN LONGEVITY REQUIREMENTS
USACE: 50-year design life is typical; however all maintenance is the local responsibility, and is subject to budgetary constraints
FEMA: Full design level required throughout actuarial policy life, NOT dependent on budgetary constraints or human intervention
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34. POSSIBLE SOLUTIONS (Chris Rasmussen, USACE)
USACE changes their optimum benefit requirement and only designs for a 100-yr event with 95% assurance for the full 50-year project life (e.g., the very few projects with benefits exceeding costs).
FEMA changes their actuarial rate calculations to allow varying levels of protection (e.g., homeowner would pay vastly higher rates reflecting a 20-yr level in year 1, a 15-yr level in year 3, etc.).

35. RECOMMENDATION Najarian Associates
Beneficially use dredged sand from offshore navigation channels to enlarge protective dune
(using geotextile tubes)
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36. MAP ACCURACY LIMITATIONS
FIRM delineations based on County’s topographic data
Aerial survey with 2-foot elevation contour intervals
Typical accuracy: about half a contour interval (~ 1 ft)
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37. ACCURACY ISSUE EXAMPLE
Our field survey crews checked the topography along 5 Hazlet streets as they crossed into the mapped A zone
Along Tavern and Central Avenue there are 4 homes that may be moved out of the FHA
Along Holly, Laurel and Pinewood there are 4 homes that should be in the FHA
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38. WHAT CAN BE DONE TO CORRECT MISTAKES?
LOMA
land survey of site
File application (Next Presentation)
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