Presented by:

Joseph L. DiLorenzo, Ph.D.NAJARIAN ASSOCIATES

COASTAL STORM CHARACTERISTICS AND CHANGES IN FLOOD INSURANCE RATE MAPS FOR COASTAL MONMOUTH COUNTY

OVERVIEW OF PRESENTATION

• Characteristics of coastal storms in New Jersey

• Changes in new FEMA Flood Insurance Rate Maps (FIRMs) for Monmouth County

• Map accuracy

Najarian Associates

TWO TYPES OF COASTAL STORMS

Tropical cyclones(hurricanes)

Najarian Associates

Extra-tropical storms

(Nor’easters)

No central eye

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

Najarian Associates

HURRICANE TRACKS (SINCE 1850)

Najarian Associates

Most hurricanes skirt NJ and weaken

HURRICANE DONNASeptember 12, 1960 at Sandy Hook

Najarian Associates

-6

-4

-2

0

2

4

6

8

9/12/600:00

9/12/606:00

9/12/6012:00

9/12/6018:00

9/13/600:00

9/13/606:00

9/13/6012:00

9/13/6018:00

9/14/600:00

EL

EV

AT

ION

(ft

, MS

L)

Predicted Observed

MSL

MONMOUTH COUNTY INUNDATION ZONES

Category 1 & 2 hurricanes since 1850

On Sept. 3, 1821, a Category 4 hurricane passed over LBI

EXTRATROPICAL STORMS (NOR’EASTERS)

– cold-core cyclonic systems

– formed in areas where strong surface temperature gradients coincide with a strong jet stream aloft

Najarian Associates

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

Najarian Associates

HISTORIC NOR’EASTERDecember 11, 1992 at Sandy Hook

-4

-2

0

2

4

6

8

12/10/9212:00

12/11/920:00

12/11/9212:00

12/12/920:00

12/12/9212:00

12/13/920:00

12/13/9212:00

12/14/920:00

EL

EV

AT

ION

(ft

,MS

L)

PREDICTED OBSERVED

MSL

TIDAL DATUMS AT SANDY HOOK

Najarian Associates

(Source: NOAA)

Sea level Datum of 1929

1.09 ft

North American Vertical Datum of 1988

Mean Sea Level

0.86 ft

Mean Lower Low Water

Mean High Water

1992 NOR’EASTER – NOAA SITES

Najarian Associates

Maximum Stillwater Elevations

Highest observed water level over ~100 year record

(January 1910 - present)

JOLINE AVENUE, LONG BRANCHDEC. 11, 1992

Najarian Associates

1992 NOR’EASTER – USGS SITES

Najarian Associates

Amplification at head of funnel-shaped Raritan Bay

Like Atlantic City maximum elevation (7.35 ft)

COASTAL FLOOD RANKINGS

Najarian Associates

RANKDATE 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

Top Eight Coastal Storms at Sandy Hook (1910-present; Source: NOAA)

FEMA’s BASE FLOOD

Najarian Associates

• 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)

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

Najarian Associates

BASE FLOOD ELEVATION (BFE)IN NO WAVE ZONES

Najarian Associates

Community100-Year Stillwater

Elevation (ft)

NGVD29 NAVD88

Highlands 10.8 9.7

Atlantic Highlands 11.6 10.5

Middletown 11.6 10.5

Keansburg 11.6 10.5

Union Beach 11.8 10.7

Keyport 11.8 10.7

Sea Bright 9 7.9

Monmouth Beach 10.1 9.0

Long Branch 8.6 7.5

Neptune 8.5 7.4

Asbury Park 8.5 7.4

Avon 8.5 7.4

Belmar 8.5 7.4

Spring Lake 8.5 7.4

Manasquan 8.5 7.4

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)

Najarian Associates

NEW FLOOD INSURANCE RATE MAPS (FIRMS)

Najarian Associates

• 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

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?

CHANGES IN THE NEW FIRMSFOR MONMOUTH COUNTY

Najarian Associates

• 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

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)

Najarian Associates

CommunityPrevious stillwater elevation (ft)

NGVD29 NAVD88

New stillwater elevation (ft)

NGVD29 NAVD88

Highlands 10.8 9.7 10.8 9.7

Atlantic Highlands 11.6 10.5 11.6 10.5

Middletown 11.6 10.5 11.6 10.5

Keansburg 11.6 10.5 11.6 10.5

Union Beach 11.8 10.7 11.8 10.7

Keyport 11.8 10.7 11.8 10.7

Sea Bright 9 7.9 9 7.9

Monmouth Beach 10.1 9.0 10.1 9.0

Long Branch 8.6 7.5 8.6 7.5

Neptune 8.5 7.4

Asbury Park 8.5 7.4 8.5 7.4

Avon 8.5 7.4

Belmar 8.5 7.4 8.5 7.4

Spring Lake 8.5 7.4 8.5 7.4

Manasquan 8.5 7.4 8.5 7.4

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

Najarian Associates

MAJOR CHANGES ALONG BAYSHORE

• Massively expanded flood hazard area due to more stringent FEMA standards for protective dunes/levees

Najarian Associates

PROJECT HISTORY

• 1968-73: Keansburg area project constructed 1968-1973. 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

Najarian Associates

PROJECT HISTORY

• 2000-2007: 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

Najarian Associates

PROJECT HISTORY

• 2007: FEMA revises standards (44 CFR 65.10-11)

– No longer considers the “levee” a levee or a protective dune

Najarian Associates

LEVEE STANDARD

• 44 CFR §65.10– 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-1988 (10.5 ft + 6.2 ft+ 1 ft)

Najarian Associates

DUNE STANDARD

• 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

Najarian Associates

PRESENT DILEMMA

• 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

Najarian Associates

ISSUE: AGENCY DISCONNECTIN 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

Najarian Associates

BIGGER DISCONNECT INLONGEVITY 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

Najarian Associates

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.).

RECOMMENDATION

• Beneficially use dredged sand from offshore navigation channels to enlarge protective dune

(using geotextile tubes)

Najarian Associates

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)

Najarian Associates

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

Najarian Associates

WHAT CAN BE DONE TO CORRECT MISTAKES?

• LOMA– land survey of site– File application (Next Presentation)

Najarian Associates