COAB-Coastal-Vulnerability-Assessment---061219-Final
Coastal Vulnerability Assessment
Planning & Community Development Department
800 Seminole Road
Atlantic Beach, FL 32233
June 2019
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Table of Contents
Executive Summary 1
Introduction 1-1
1.1 Overview 1-1
1.2 Coastal Resiliency Planning in Florida 1-2
1.3 About this Project 1-2
1.4 Scope of the Vulnerability Assessment 1-4
Methodology 2-1
2.1 General Methodology 2-1
2.2 Sea Level Rise Projections 2-2
2.3 Nuisance Flooding 2-5
2.4 Future Flood Risk 2-6
2.4.1 Storm Surge Modeling 2-6
2.4.2 Stormwater Inundation Modeling 2-8
2.4.3 Combined Inundation 2-9
Future Conditions with Sea Level Rise 3-1
3.1 Projected Mean Higher High Water Levels 3-1
3.2 Projected Extents of Nuisance Flooding 3-2
3.3 Projected 100-Year Event Storm Surge 3-3
3.4 Projected Rainfall Induced Flooding 3-4
3.5 Projected 100-Year Storm Event Flood 3-5
Vulnerability Assessment 4-1
4.1 Properties and Buildings 4-1
4.2 Critical Facilities 4-2
4.2.1 Critical Facilities and Sea Level Rise - 2044 and 2069 4-2
4.2.2 Critical Facilities and Nuisance Flooding - 2044 and 2069 4-3
4.2.3 Critical Facilities and Future Flood Risk Maps for 2044 and 2069 4-3
4.2.4 Summary of Critical Facilities Vulnerability 4-5
Next Steps 5-1
5.1 Adaptation Planning 5-1
References 6-1
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Appendices
Appendix A – Coastal Flooding Assessment – Applied Technology & Management, Inc.
Appendix B – Vulnerability Assessment Tech Memo – Jones Edmunds & Associates
Appendix C – Future 100-Yr Flood Risk Maps
List of Tables
Table 2-1 - Projected Future Mean Sea Levels - Mayport Bar Pilot’s Dock (ft - NAVD88) ....... 2-2
Table 2-2 – Projected Sea Level Rise – NOAA Intermediate High 2017 ................................. 2-3
Table 4-1 – Vulnerability of Property ....................................................................................... 4-1
Table 4-2 – Summary Critical Facilities Vulnerability by Scenario ........................................... 4-5
List of Figures
Figure 1-1 – Atlantic Beach Zoning Map ................................................................................. 1-1
Figure 1-2 – Global Average Sea Level Change (US Global Change Research Program) ...... 1-3
Figure 1-3 – Relative Sea Level Rise – Mayport Bar Pilot’s Dock (NOAA) .............................. 1-4
Figure 2-1 – Comparison of Projected Sea Level Rise Data Sets............................................ 2-2
Figure 2-2 – Hurricane Matthew Water Levels - October 2016 at Mayport Bar Pilot’s Dock .... 2-3
Figure 2-3 – Hurricane Irma Water Levels - September 2017 at Mayport Bar Pilot’s Dock ...... 2-4
Figure 2-4 – Comparison of Matthew and Irma Water Levels with Projected Mean SLR ......... 2-4
Figure 2-5 – Annual Exceedance Probability Curve – Mayport Bar Pilot’s Dock (NOAA) ........ 2-5
Figure 2-6 – Illustration of a Coastal Wave Transect ............................................................... 2-7
Figure 2-7 – Illustration of Modeling Effects of Sea Level Rise ................................................ 2-7
Figure 2-8 – Future Conditions Impervious Update Area ......................................................... 2-8
Figure 3-1– NOAA 2017 Intermediate-High SLR Projects for 2044, 2069 and 2119 ................ 3-1
Figure 3-2 – Projected Nuisance Flooding Due to SLR ........................................................... 3-2
Figure 3-3 – Projected 100-Year Event Storm Surge .............................................................. 3-3
Figure 3-4 – Projected 100-Year Storm Event Rainfall Induced Flooding ................................ 3-4
Figure 3-5 – Projected 100-Year Storm Event Flood ............................................................... 3-5
Figure 4-1 – Location of Critical Facilities in Proximity to SLR for 2044 and 2069 ................... 4-2
Figure 4-2 – Location of Critical Facilities in Proximity to Nuisance Flooding .......................... 4-3
Figure 4-3 – Critical Facilities and Future Flood Risk Maps for 2044 and 2069 ....................... 4-4
Coastal Vulnerability Assessment
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Executive Summary
Sea levels have risen measurably over the years in Atlantic Beach. The question is how will this
rate of sea level rise change in the future and how will it affect us as a City?
To help answer these questions, the City embarked on a study to evaluate the vulnerability of the
City with respect to nuisance flooding and storm induced flooding from sea level rise in the 25-,
50- and 100-year timeframe. This report details the methodology utilized to develop a statistically
based approach to vulnerability from sea level rise and assessed the vulnerability of critical
facilities and infrastructure. The assessment also included an evaluation of the potential impact
to all properties and structures within the city limits.
The results of this effort are series of maps that are essentially future versions of the FEMA Flood
Insurance Rate Maps utilized for planning and building requirements today. The analysis reveals
that there may be significant future impacts from sea level rise in the not so distant future that will
have to be taken into account with respect to planning, development and redevelopment.
This report forms the basis for the next step in planning for the impacts of sea level rise through
development of an adaptation plan. The adaptation plan will consider policies, planning
measures, future projects, etc. to help adapt to and mitigate for impacts to vulnerable areas of the
City.
This project was made possible by a Resiliency Planning Grant provided by the Florida
Department of Environmental Protection’s Resilient Coastlines program. Special thanks to
Whitney Grey and Angel Baratta for their assistance.
The following City of Atlantic Beach staff provided content:
Shane Corbin; AICP, Director of Planning
Steve Swann; P.E., City Engineer
Amanda Askew; AICP, Principle Planner
Brian Broedell; AICP, Planner
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Introduction
1.1 Overview
The City of Atlantic Beach is one of three small coastal communities in northeast Florida that
make up the “Beaches” of Jacksonville. The City consists of three square miles with a population
of approximately 14,000, is located between two miles of Atlantic Ocean beachfront on the east
and the expansive marsh and estuarine environment of the San Pablo Creek / Atlantic Intracoastal
Waterway (AICW) on the west. Atlantic Beach is a near fully-developed municipality where the
predominant land use is residential consisting of stable and well-established neighborhoods.
Figure 1-1 – Atlantic Beach Zoning Map
Atlantic Beach contains two commercial corridors: the north side of Atlantic Boulevard (SR10)
extending from the ocean westerly to the AICW, and Mayport Road (SR A1A), extending from
Atlantic Boulevard northerly to the municipal limits of the City at Dutton Island Road.
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The City possesses a unique character and “personality” where a high quality of life, diverse
recreational activities, preservation of community character and protection of natural resources
are priorities to both residents and elected officials. Since the City is near full build out, current
development consists of redevelopment and scattered infill. In 2019, City staff began observing
the development of lots that were historically untouched primarily due to low lying topography and
proximity to the 100-year floodplain. This trend is likely due to a lack of undeveloped land and the
continued attractiveness of the area.
1.2 Coastal Resiliency Planning in Florida
Scientists from around the world have been studying climate change and the resulting sea level
rise impacts for decades. Today, multiple sources of data are available to predict realistic
scenarios of future sea levels and their impacts on coastal communities. Some cities, such as
Miami, are already seeing impacts from sea level changes prompting immediate adaptation
measures.
The state of Florida began their first organized adaptation planning efforts in 2009 which led to
the Community Planning Act (CPA) in 2011. The CPA gave local governments the option to create
adaptation plans. However, the state did not require municipalities to address sea level rise until
2015 when the “Peril of Flood” statute was passed which forced municipalities to address sea
level rise in their comprehensive plans. Atlantic Beach incorporated “Peril of Flood” amendments
in to its comprehensive plan in 2019.
In 2018, recognizing the need for coastal communities to assess potential impacts from sea level
rise, the Florida Department of Environmental Protection’s Resilient Coastlines Program awarded
its 16 resiliency planning grants to coastal communities including Atlantic Beach. The purpose of
Atlantic Beach’s grant is to provide funding for planning purposes to help prepare our community
for current and future effects of rising sea levels, initially through the preparation of this
Vulnerability Assessment.
1.3 About this Project
On average globally, the sea level has risen by about 8 inches since scientific record keeping
began in 1880. This rate has increased in recent decades to a little more than an inch per decade.
Global average sea level has risen by about 7–8 inches (about 16–21 cm) since 1900, with about
3 of those inches occurring since 1993. In addition to the global average sea level rise, local sea
level rise – sometimes called “relative sea level rise” – happens at different rates in different
places. Local sea level rise is affected by the global sea level rise, but also by local land motions,
and the effects of tides, currents, and winds.
Figure 1-2 shows an increase in global average sea level since 1880, in inches. Note that the
blue line, tide gauge data, becomes steeper in more recent decades. This indicates an increasing
rate of change. The surrounding light blue-shaded area shows upper and lower 95% confidence
intervals and the orange line shows sea level as measured by satellites for comparison (1993-
2016). (U.S. Global Change Research Program, 2017)
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As sea levels have risen, the incidence of nuisance flooding or “sunny day” flooding during spring
tide events at certain times of the year have increased five to ten fold since the 1960s in several
U.S. coastal cities and rates of increase are accelerating in over 25 Atlantic and Gulf Coast cities.
In Atlantic Beach, nuisance flooding resulting in overtopped roads is occurring now in areas of
Atlantic Beach such as Dutton Island Road and West Plaza.
Figure 1-2 – Global Average Sea Level Change (US Global Change Research Program)
The closest National Oceanic and Atmospheric Association (NOAA) primary tidal gauge to
Atlantic Beach is located at the Mayport Bar Pilot’s Dock (NOAA tide gauge No. 8720218) near
the ferry slip. Figure 1-3 depicts the relative change is sea level at the Mayport Bar Pilot’s Dock
over the 90-year history of this station. The current local rate of sea level change is approximately
one-inch every decade. (https://tidesandcurrents.noaa.gov/sltrends/)
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Figure 1-3 – Relative Sea Level Rise – Mayport Bar Pilot’s Dock (NOAA)
Although there is uncertainty relating to the change in rate of sea level rise, there is no uncertainty
that sea level is rising in our area. As sea levels rise, incidents of nuisance flooding will increase
and flooding due to severe weather events will affect larger areas of the City. To aid in both
planning and assessing the City’s potential vulnerability under future scenarios with higher sea
levels, the City conducted a rigorous technical analysis to determine just what those effects may
be and how they will impact residents and critical infrastructure.
1.4 Scope of the Vulnerability Assessment
The vulnerability assessment is focused on providing a quantitative analysis of property,
infrastructure and habitats within the City’s municipal boundaries under future predicted sea level
scenarios using widely accepted scientific analyses.
To complete the analyses required to make these predictions, the City selected two engineering
consulting firms, Jones Edmunds & Associates and Applied Technology & Management, Inc.
(ATM). Both firms have many years of local experience as well as experience conducting similar
analyses throughout the coastal areas of the Southeast United States. Their task was to perform
an analysis of potential future flood risks under projected sea level rise, storm surge and rainfall
induced flooding scenarios to provide geographic information systems (GIS) based predictive
flood risk map layers for years 2044, 2069 and 2119. City staff then utilized these GIS maps to
perform a vulnerability assessment of sea level rise within its municipal boundaries for 2044 and
2069. Only years 2044 and 2069 are used for the vulnerability assessment due to the level of
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uncertainty beyond 50 years. In addition, most infrastructure and many buildings only have a life
span of 50 years.
The technical analyses that form the basis of the vulnerability assessment began with the current
Federal Emergency Management Association (FEMA) Flood Insurance Rate Maps (FIRMs) as
the baseline condition and utilized NOAA 2017 Intermediate-High Sea Level Rise (SLR) scenarios
for predicted 2044, 2069 and 2119 conditions as follows:
Mean Higher High Water (MHHW) modeling to predict frequency of nuisance flooding
Storm surge modeling to predict coastal flooding
Stormwater modeling to predict upland rain induced flooding
Composite coastal flooding and upland rain induced flood mapping to delineate future
flood hazard areas
Assessment of property, infrastructure and habitat impacted within flood zones of
composite future flood mapping
MHHW is the higher of the two daily tides averaged over a 19-year tidal epoch. The
methodology is summarized in Section 2 and the results of these analyses are presented in
Sections 3 & 4 of this report. A more detailed description of the methodology is attached in
Appendices A & B.
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Methodology
2.1 General Methodology
For this vulnerability assessment, the baseline is the existing mean higher high water (MHHW)
level and the current FEMA FIRMs for the City. The MHHW level, which is the average of the
higher of each of the two daily high tides, provides an indication of the frequency of sunny day
flooding occurrences due to normal tidal cycles and does not include storm events.
The FIRMs for the City of Atlantic Beach provide a prediction of what the 100-year flood event
water levels will be. While FEMA does not consider sea level rise (SLR) in the development of a
FIRM, they do conduct a rigorous analysis of storm surge flooding and flooding due to upland
inundation from rainfall. FIRMs are currently used to map properties with respect to the 100-year
flood event to set flood insurance premiums as well as to determine where stricter building and
development standards apply for flood protection.
Given the common use of FIRMs for regulatory purposes and general familiarity many people
have with these maps, this vulnerability assessment utilizes the FEMA methodology to predict the
extents of a 100-year flood event in the future considering the effects of SLR. The technical
analyses that serve as the foundation for this vulnerability assessment resulted in essentially
producing maps of what the FIRM may look like in 25, 50 and 100 years considering sea level
rise. The analyses also incorporated the loss of soil storage that may result from rising sea levels
as well as predicted future build-out conditions within the city boundaries.
Surge analyses were conducted for both the Atlantic Ocean side of the City and the Intracoastal
Waterway side of the City utilizing the same methodology FEMA used to develop the FIRMs for
this area. It is important to note that as water depth increase with SLR, there is a corresponding
increase wave heights and wave runup. Hence, the surge analyses being specifically analyzed
with future water level conditions and not just added to the predicted increased sea level height.
Upland rainfall induced flooding was analyzed using the Interconnected Pond Routing (ICPR)
model developed for the City’s 2018 Stormwater Master Plan Update for every drainage basin
within the City. This was a necessary step given the flat topography of the City and impacts of
tide height on the performance of the drainage systems.
Both analyses utilized current conditions as a reference check and used the intermediate-high
NOAA 2017 SLR projections. Surge analyses were conducted for the 25-, 50- and 100-year
planning horizons to develop future 100-yr storm event predictions. Upland flooding analyses
utilized the same planning horizon to develop associated flood risks from the 10-, 25- and 100-
year return period storm events for each time period. The future storm surge flood risk maps that
were produced were then combined with the rainfall-induced flood risk for the 100-year return
period storm to produce a spatial estimate of future flood risks. MHHW mapping over the same
planning horizons were also produced to assess areas where increased sunny day nuisance
flooding might be expected.
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2.2 Sea Level Rise Projections
A comparison review regarding the projected local sea level rise was performed at the Mayport
Bar Pilot’s Dock NOAA tide gauge No. 8720218 which is the closest gauge to the City. The
projected local sea-level-rise estimates examined were for years 2044, 2069, and 2119 (i.e., the
25-, 50-, and 100-year scenarios). Several studies have published projected SLR estimates at
this gauge and are presented graphically in Figure 2-1 and in tabular form in Table 2-1.
Figure 2-1 – Comparison of Projected Sea Level Rise Data Sets
Table 2-1 - Projected Future Mean Sea Levels - Mayport Bar Pilot’s Dock (ft - NAVD88)
Year USACE 2013 NOAA 2012 CARSWG 2016 NOAA 2017 IPCC AR5
RCP 8.5
Int High Int-
High High Medium High Highest Int Int-
High High Extreme Median
2044 0.1 0.86 0.63 1.24 0.48 0.86 1.24 0.54 1.00 1.45 1.83 0.28
2069 0.58 2.25 1.74 3.08 1.41 2.24 3.08 1.53 2.58 3.73 4.63 0.96
2119 1.86 6.4 5.03 8.66 4.13 6.4 8.66 3.77 6.69 10.53 13.62 2.90
The NOAA 2017 intermediate-high data was chosen for this effort due to its general acceptance
as a moderate estimate of future sea level conditions and its use in other communities throughout
Florida. Table 2-2 summarizes the selected sea level rise scenarios utilized in this vulnerability
assessment.
0
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CARSWG 2016 - Highest
USACE 2013 - High
USACE 2013 - Int
IPCC AR5 RCP 8.5 - Median
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Table 2-2 – Projected Sea Level Rise – NOAA Intermediate High 2017
Scenario
Projected Sea Level Rise
(Feet)
Tidal Boundary Stage*
(Feet NAVD 1988)
2019 0 2.00
2044 1.06 3.06
2069 2.65 4.65
2119 6.75 8.75
* Predicted future mean higher high water (MHHW) level
For comparison, water elevations recorded during Hurricane Matthew in October 2016 and
Hurricane Irma in September 2017 are presented below. The highest water level recorded during
Hurricane Matthew was 5.23 feet NAVD88 and was 5.58 feet NAVD88 during Hurricane Irma.
Figure 2-4 compares estimated future sea levels with the highest tides from these two events.
Figure 2-2 – Hurricane Matthew Water Levels - October 2016 at Mayport Bar Pilot’s Dock
-2
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10/6/2016 10/7/2016 10/8/2016 10/9/2016
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Figure 2-3 – Hurricane Irma Water Levels - September 2017 at Mayport Bar Pilot’s Dock
Figure 2-4 – Comparison of Matthew and Irma Water Levels with Projected Mean SLR
-2
-1
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2.3 Nuisance Flooding
Nuisance flooding, sometimes referred to as "sunny day" flooding, is flooding that leads to public
inconveniences such as road closures. The City currently experiences a limited degree of
nuisance flooding in several locations. As sea levels continue to rise, nuisance flooding will
become more prevalent and extensive.
For this effort, nuisance flooding is considered to be occurring when the tide level is approximately
one foot greater than the Mean Higher High Water (MHHW) level at Mayport. This occurs at least
once every year as can be seen in the statistical summary presented in Figure 2-5. This chart
indicates that there is 99% probability of water levels exceeding MHHW by at least 1’ (0.3 m) on
an annual basis. Similarly, there is a 50% probability of tidal levels exceeding MHHW by 1.5’
(0.45 m) in any given year and a 10% probability of tidal levels exceeding MMHW by 2’ (0.6 m) in
any given year.
The current MHHW level in our area is at elevation 2’, and based on observations, nuisance
flooding can start to occur when water levels exceed 3’. Areas of the City that are at or below 3’
elevation include the Dutton Island access road and portions of West Plaza, both areas that
currently experience nuisance flooding. Given that there is a 99% probability of water levels of at
least 1’ above MHHW occurring on annual basis as shown on Figure 2-5, nuisance flooding in
portions of Atlantic Beach is expected to occur at least once every year at a minimum.
Figure 2-5 – Annual Exceedance Probability Curve – Mayport Bar Pilot’s Dock (NOAA)
To estimate nuisance flooding in the future, NOAA’s Digital Coast tools were utilized to overlay
one foot of water level on top of the predicted sea level rise over the planning period. As updated
digital elevation models become available, the City will undertake a more rigorous analysis of the
future frequency and extent of nuisance flooding will update the Vulnerability Assessment as
necessary.
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2.4 Future Flood Risk
As sea levels rise there will generally be an increase in flood risk. This increased risk is not
reflected in the current FEMA Flood Insurance Rate Maps (FIRMs) for the City. Estimating the
extent of future risk requires updating the FIRMs to account for impacts in both storm surge and
rainfall induced flooding under higher sea level conditions. The following sections describe the
methodology utilized to develop the information required to assess the future flood risk for the
City.
2.4.1 Storm Surge Modeling
Rising sea level will result in increased storm surge levels and wave heights as well as exacerbate
nuisance flooding from extreme high tides. The combination of a higher sea level with a storm
surge can result in larger storm impacts and coastal vulnerability from a flooding perspective than
are currently experienced.
FIRMs are updated on a regular basis (typically every 10 years) and FEMA only considers the
existing mean sea level at the time of the update and does not account for SLR. For the
vulnerability assessment, an analysis based on the FEMA flood mapping protocol was conducted
to evaluate coastal flooding and wave risks under projected SLR scenarios for 25, 50 and 100
years.
The storm surge modeling utilized existing FEMA stillwater elevation (SWEL) results (that don’t
include waves) for a 100-year event and increased the elevations to account for the projected
increase in sea levels in the future. The next step required updating wave transect modeling on
top of the increased SWEL elevations to predict 100-year base flood elevations under future
higher sea levels. Figure 2-6 depicts a typical FIRM cross-section and the concept of SWEL and
wave setup on top of the SWEL. Appendix A contains a detailed description of this approach.
Note that wave modeling is very sensitive to water depth and increased future sea levels will allow
larger waves to travel further inland during storms because there is more area inundated with
higher future SWEL. This is illustrated in Figure 2-7. The result of these analyses were FIRM type
flood maps for future higher sea level scenarios.
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Figure 2-6 – Illustration of a Coastal Wave Transect
Figure 2-7 – Illustration of Modeling Effects of Sea Level Rise
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2.4.2 Stormwater Inundation Modeling
To determine how rainfall-induced flooding may be impacted by sea level rise and new
development within the City, the hydrologic and hydraulic parameters in the Interconnected Pond
Routing (ICPR) Version 4 models that were developed during the City’s 2018 Stormwater Master
Plan update were adjusted to reflect projected increases in impervious area from future
development, increased boundary conditions and node initial conditions from rising sea levels,
and reduced soil storage from rising sea levels.
The rates of future development that were developed for the City’s 2018 Stormwater Master Plan
update were used to estimate the impervious area in the City in 2044, 2069 and 2119. The
estimated future impervious values were applied to the already modeled stormwater drainage
basins so that modeled runoff accurately reflects future conditions. The areas updated for future
increases in impervious area for the 2044, 2069 and 2119 conditions are shown in Figure 2-8.
Figure 2-8 – Future Conditions Impervious Update Area
The ground water table is also expected to rise with rising sea levels because of consistently
higher tides. This increase in ground water levels will reduce the amount of soil storage available
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for rainfall to infiltrate and will increase the volume of runoff during storm events. The decrease in
soil storage will be more marked in areas directly adjacent to the coastline and will be reduced
further inland. To account for these projected changes, the basin criteria in the stormwater model
were adjusted to decrease soil storage capacity in conjunction with expected future sea level
elevations.
Peak stage results from the future drainage conditions models were used to map the predicted
rainfall-induced flood risk in the City in 2044, 2069 and 2119 for a series of 24-hour rain events
including the 100-year return period rainfall events The results were then mapped using the 5-
foot-by-5-foot digital elevation model (DEM) generated from the 2007 City of Jacksonville Light
Detection and Ranging (LiDAR) data. Note that this does not account for grading changes that
have occurred since the LiDAR was collected, including the grading changes at the Atlantic Beach
Country Club. The models will be updated if necessary when newer data is available, expected
late 2019. See Appendix B for a detailed description of this modeling approach.
2.4.3 Combined Inundation
The future storm surge flood risk maps were then combined with the rainfall induced inundation
maps for the 100-year return period storm for 2044, 2069 and 2119. These maps are attached as
Appendix C separately. Where there was overlap between the flood risk mapping, the higher
inundation estimate from the two mapping efforts was selected. These maps provide for a spatial
estimate of future flood risk that will serve as the basis for the vulnerability assessment.
Note that rainfall induced flood risk and coastal surge flood risk are usually evaluated relatively
independently because the two forms of flood risk are neither fully dependent nor fully
independent. Therefore, traditional statistical approaches are not applicable and the standard
procedure to deal with this is to evaluate the two independently using common sea level rise
scenarios and then take the higher of the combined identified risk at each location.
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Future Conditions with Sea Level Rise
3.1 Projected Mean Higher High Water Levels
Figure 3-1 depicts the extent of Mean Higher High Water (MHHW) levels, the average of the
higher of the daily high tides over a 19 year tidal epoch for NOAA’s intermediate-High sea level
rise projections for years 2044, 2069 and 2119 in Atlantic Beach. This is also referred to as a
“bathtub model” because the higher water levels are just mapped to fill in areas of the City below
the projected MHHW level. This model does not incorporate rainfall induced flooding or storm
surge. The boundaries shown in this figure project where the future shoreline may be located
absent any adaptative measures.
Figure 3-1– NOAA 2017 Intermediate-High SLR Projects for 2044, 2069 and 2119
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3.2 Projected Extents of Nuisance Flooding
Figure 3-2 depicts nuisance, or sunny day, flooding that the City may experience based on
anticipated sea level rise. The mapped extent of projected nuisance flooding is based on the
annual probability of experiencing tide levels of at least 1 foot greater than the MHHW.
Figure 3-2 – Projected Nuisance Flooding Due to SLR
Future nuisance flooding is predicted to increase substantially on the western side of the City
adjacent to the Intracoastal Waterway and along Sherman Creek and the Aquatic Gardens
neighborhood. Nuisance flooding seaward of the mapped extents are expected to be more
frequent than an annual event.
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3.3 Projected 100-Year Event Storm Surge
Figure 3-3 illustrates the projected extent of the storm surge expected from a 100-year storm
event in Atlantic Beach in 2044, 2069 and 2119. This map builds on the previous “bathtub model”
by predicting the potential extent of future storm surge resulting from increased sea levels during
a 100-year storm event. Note that sea level projections for 2119 have a very high degree of
uncertainty and is shown here for illustrative purposes only.
Figure 3-3 – Projected 100-Year Event Storm Surge
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3.4 Projected Rainfall Induced Flooding
Figure 3-4 illustrates the projected rainfall induced flooding from a 100 year storm in Atlantic
Beach for years 2044, 2069 and 2119. This map reflects future conditions with increased
impervious surface from development. In addition, stormwater infrastructure is inhibited and the
water table is elevated due to sea level rise projections. This map is combined with the projected
previous storm surge map to create the projected 100 Year Future Flood Zones used in the
vulnerability assessment
Figure 3-4 – Projected 100-Year Storm Event Rainfall Induced Flooding
.
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3.5 Projected 100-Year Storm Event Flood
Figure 3-5 illustrates the extent of a projected 100-year storm event for years 2044, 2069 and
2119 by combining the previous 2 maps (Figure 3-4 and Figure 3-5). This map was developed
using the same process FEMA utilized to create current Flood Insurance Rate Maps that depict
the current extent of flooding expected from a 100-Year storm event. The extent of flooding from
a 100-year storm event associated with projected sea levels in 2119 are provided for illustrative
purposes only. The 2044 and 2069 scenarios are used for the Vulnerability Assessment due to
the high level of uncertainty in sea level rise projections beyond 50 years.
Figure 3-5 – Projected 100-Year Storm Event Flood
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Vulnerability Assessment
4.1 Properties and Buildings
Based on the projected impacts of sea level rise, there will likely be additional properties in the
future that will be subject to both nuisance flooding and located within a Special Flood Hazard
Area (SFHA, which is the area inundated by flood waters from a 100-year storm event). Table 4-
1 illustrates the total value of land and buildings impacted for the bathtub model, nuisance flooding
and projected 100 year flood risk maps for 2044 and 2069. For the 100 year flood risk assessment,
parcels were only counted if water was projected to reach their center. Counting every parcel
touched would have included beach front parcels which are actually at higher elevations and
typically have higher assessed values. All values are provided in today’s dollar.
Table 4-1 – Vulnerability of Property
2044
Scenarios
Number of
Parcels
Impacted (% of
All Parcels)
Number of
Buildings on
Impacted
Parcels
Land Value
of Impacted
Parcels
Building Value
of Impacted
Parcels
Taxable Value
of Impacted
Parcels
SLR Only 180 (3%) 302 $26,554,830 $81,875,481 $82,960,215
Nuisance
Flooding 249 (4%) 370 $29,661,062 $100,480,967 $112,541,757
100-Yr Flood
Risk 1260 (20%) 1296 $126,371,130 $242,039,789 $287,288,200
2069
Scenarios
Number of
Parcels
Impacted (% of
All Parcels)
Number of
Buildings on
Impacted
Parcels
Land Value
of Impacted
Parcels
Building Value
of Impacted
Parcels
Taxable Value
of Impacted
Parcels
SLR Only 261 (4%) 380 $31,589,467 $93,090,754 $97,408,620
2069
Nuisance
Flooding
797 (13%) 902 $90,618,199 $193,768,543 $232,210,034
2069 100-Yr
Flood Risk 2371 (38%) 2360 $270,534,021 $436,009,087 $603,815,032
Nuisance flooding totals are important because they reflect what is likely to happen at least
annually year. By 2069, nuisance flooding is predicted to impact 13% of properties in Atlantic
Beach totaling $232,210,034 in taxable value. In 2069, 38% of properties will fall within the
projected 100 year flood risk map totaling $603,815,032 in taxable value.
Existing development standards in place will help mitigate the impacts from sea level rise on
property up to a certain point. These standards relate to the required minimum finished floor
elevation (FFE) for all new construction that creates a buffer between flood water and living areas.
The City currently requires a minimum finished floor elevation of 7.5 feet above mean sea level
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or 2.5 feet above the 100- year flood elevation or base flood elevation (BFE) per Chapter 24, Sec.
24-251(c) of the Land Development Code. However, the buffer provided by FFE standards that
apply today to properties located in a SFHA will be reduced in the future as sea levels rise. Note
that many structures currently located in a SFHA were built before these standards were required
and will experience higher risk unless they are elevated.
4.2 Critical Facilities
4.2.1 Critical Facilities and Sea Level Rise - 2044 and 2069
The impact of SLR with respect to the vulnerability of critical facilities and infrastructure within the
City is important with respect to planning. Critical facilities and infrastructure within the city limits
located within areas subject to future inundation were picked up in the assessment. Facilities and
infrastructure located outside of the city limits are noted and will be assessed in a separately to
this report. The assessment showed no direct impacts from the projected sea level in 2044 and
direct impact to one wastewater lift station from the 2069 projection. However, one additional lift
station, the City Commission Chambers, and sections of five of the nine critical roadways are
located within just twenty feet of the projected 2069 sea level.
Figure 4-1 – Location of Critical Facilities in Proximity to SLR for 2044 and 2069
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4.2.2 Critical Facilities and Nuisance Flooding - 2044 and 2069
An assessment of critical facilities and infrastructure within the city was also completed for
projected nuisance flooding in years 25 and 50. The results show one lift station projected to be
impacted by nuisance flooding in 2044 and four lift stations projected to be impacted in 2069.
Further, the models show the City Commission Chambers, the City Hall parking lot, and various
sections of critical roadways may be prone to nuisance flooding by 2069.
Figure 4-2 – Location of Critical Facilities in Proximity to Nuisance Flooding
4.2.3 Critical Facilities and Future Flood Risk Maps for 2044 and 2069
Using the projected 100-year flood zones in 2044 and 2069, an assessment of critical facilities
and infrastructure within the city limits was completed. In both scenarios, critical facilities including
the Police and Fire Station, City Hall, the Gail Baker Community Center, and Atlantic Beach
Elementary School are located within the projected flood zones. In addition, the only water plant
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located within city limits, four gas stations, and sections of all nine identified critical roadways are
within both flood zone scenarios. Lastly, one potable water well is within the projected 2044 flood
zone and two potable water wells are located within the projected 2069 flood zone.
Figure 4-3 – Critical Facilities and Future Flood Risk Maps for 2044 and 2069
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4.2.4 Summary of Critical Facilities Vulnerability
Table 4-2 summarizes the projected vulnerability of critical facilities for Atlantic Beach for the 25-
and 50-year scenarios (2044 and 2069). As depicted in this table, sea level rise alone is not
projected to become problematic for critical facilities until 2069. However, nuisance flooding in
conjunction with sea level rise begins to impact wastewater and transportation infrastructure by
2069.
Table 4-2 – Summary Critical Facilities Vulnerability by Scenario
2044
Scenarios
Critical
Roads
City
Hall,
Police
& Fire
Station
Public
Utilities
Facility
Public
Works
Facility
Lift
Stations
(#)
Potable
Water
Wells
(#)
Potable
Water
Plants
(#)
Waste-
water
Facility
Atlantic
Beach
Elem.
School
Adele
Grage
Center
Gail
Baker
Center
Jordan
Park
Center
Gas
Stations
(#)
SLR Only N N N N N N N N N N N N N
Nuisance
Flooding N N N N Y (1) N N N N N N N N
100-Yr
Flood
Risk
Y (9)* Y N N Y (10) Y (1) Y (1) N Y N Y N Y (4)
* Portions of Atlantic Blvd, Seminole Rd, Mayport Rd, Sherry Dr, Dutton Island Rd, Levy Rd, Plaza,
Main St & Selva Marina Dr
2069
Scenarios
Critical
Roads
City
Hall,
Police
& Fire
Station
Public
Utilities
Facility
Public
Works
Facility
Lift
Stations
(#)
Potable
Water
Wells
(#)
Potable
Water
Plants
(#)
Waste-
water
Facility
Atlantic
Beach
Elem.
School
Adele
Grage
Center
Gail
Baker
Center
Jordan
Park
Center
Gas
Stations
(#)
SLR Only N N N N Y (1) N N N N N N N N
Nuisance
Flooding Y (3)** N N N Y (7) Y (2) Y (1) N N N N N N
100-Yr
Flood Y (9)* Y N N Y (11) Y (2) Y (1) N Y N Y N Y (4)
* Portions of Atlantic Blvd, Seminole Rd, Mayport Rd, Sherry Dr, Dutton Island Rd, Levy Rd, Plaza,
Main St & Selva Marina Dr
** Portions of Seminole Rd, Levy Rd, & Selva Marina Dr
The projected 100-year floodplain in 2044 and 2069 is expected to significantly encroach on
critical facilities. This projected encroachment has implications for critical facility planning as
discussed in Section 5.0.
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Next Steps
5.1 Adaptation Planning
There is good news. The City of Atlantic Beach has time plan for the future and minimize the
negative impacts associated with SLR. The next step is for the City to begin an adaptation
planning process. The adaptation planning process would engage stakeholders to evaluate SLR
predictions and consider what actions, if any, should be taken. The Florida Department of
Economic Development (DEO) has resources available to assist local governments in this
process and multiple communities have already completed their adaptation plans.
DEO describes the following 5 strategies for adaptation planning:
1. Protection - Protection strategies involve "hard" and "soft" structurally defensive measures
to mitigate the impacts of current and future flooding, such as seawalls or beach
renourishment, in order to maintain existing development.
2. Accommodation - Accommodation strategies do not act as a barrier to inundation but rather
alter the design, construction, and use of structures to handle periodic flooding. Examples
include elevating structures and stormwater retrofits that improve drainage or use natural
areas to soak up or store water and runoff (i.e., green infrastructure).
3. Strategic Relocation - Strategic relocation involves the possible relocation of existing
development to safer areas through voluntary or incentivized measures in populated, hazard
prone areas that reduce the intensity of development and/or gradually increase setbacks over
time. Such options usually involve the transition of vulnerable land from private to public
ownership, but may also include other strategies such as transfer of development rights,
purchase of development rights, and rolling easements.
4. Avoidance - Avoidance involves anticipatory actions taken to direct new development away
from vulnerable lands to safer areas. Examples include land conservation, conservation
easements, transfer of development rights, and increased coastal setbacks.
5. Procedural - Procedural strategies aim to generate vulnerability and adaptation information,
increase awareness of vulnerabilities and adaptation options, or incorporate such information
into plans or policies. Examples include vulnerability assessments, community outreach and
education activities, new comprehensive plan language addressing sea level rise, and real
estate disclosures.
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References
2015 Unified Sea Level Rise Projection for Southeast Florida, Southeast Florida Regional
Climate Change Compact Sea Level Rise Work Group, 2015
Climate Science Special Report: Fourth National Climate Assessment, U.S. Global Change
Research Program, 2017
Contribution of Working Groups I, II and III to the Fifth Assessment Report of the
Intergovernmental Panel on Climate Change (IPCC) Climate Change 2014: Synthesis
Report, 2014
Adaptation Planning – Florida Department of Economic Opportunity
(http://www.floridajobs.org/community-planning-and-development/programs/community-
planning-table-of-contents/adaptation-planning)
Global and Regional Sea Level Rise Scenarios for the U.S., NOAA Technical Report NOS CO-
OPS 083, 2017
Global Sea Level Rise Scenarios for the United States, NOAA Technical Report OAR CPO-1
National Climate Assessment, 2012
Incorporating Sea Level Changes in Civil Works Programs, USACE Engineer Regulation (ER)
1100-2-8162, 2013
NOAA Tides & Currents – Water Levels (https://tidesandcurrents.noaa.gov/sltrends/)
Regional Sea Level Scenarios for Coastal Risk Management Report, Coastal Assessment
Regional Scenario Working Group (CARSWG) 2016