Credit ©GaryJ.Kohn

Global and Regional Sea Level Rise 

Scenarios for the United States
Global and Regional Sea Level Rise Scenarios for the United States | ii

Cover Image: Flooding from 15-knot northerly winds on Smith Island, Maryland, on November 23, 2015. 

Credit ©Gary J. Kohn

National Oceanic and Atmospheric Administration

U.S. Department of Commerce

National Ocean Service

Silver Spring, Maryland

February, 2022

Recommended Citation:

Sweet, W.V., B.D. Hamlington, R.E. Kopp, C.P. Weaver, P.L. Barnard, D. Bekaert, W. Brooks, 

M. Craghan, G. Dusek, T. Frederikse, G. Garner, A.S. Genz, J.P. Krasting, E. Larour, D. Marcy,

J.J. Marra, J. Obeysekera, M. Osler, M. Pendleton, D. Roman, L. Schmied, W. Veatch, K.D. White,

and C. Zuzak, 2022: Global and Regional Sea Level Rise Scenarios for the United States: Updated Mean Projections and Extreme Water Level Probabilities Along U.S. Coastlines. NOAA

Technical Report NOS 01. National Oceanic and Atmospheric Administration, National Ocean

Service, Silver Spring, MD, 111 pp. https://oceanservice.noaa.gov/hazards/sealevelrise/noaa-nostechrpt01-global-regional-SLR-scenarios-US.pdf
Global and Regional Sea Level Rise Scenarios for the United States | iii

Global and Regional Sea Level Rise 

Scenarios for the United States: 

Updated Mean Projections and 

Extreme Water Level Probabilities 

Along U.S. Coastlines

Notice:

Mention of a commercial company or product does not constitute an endorsement by NOAA. Use of information from this publication for 

publicity or advertising purposes concerning proprietary products or the tests of such products is not authorized.

Authors

William V. Sweet 

NOAA National Ocean Service

Benjamin D. Hamlington 

NASA Jet Propulsion Laboratory,

California Institute of Technology 

Robert E. Kopp

Rutgers University

Christopher P. Weaver

U.S. Environmental Protection Agency

Patrick L. Barnard

U.S. Geological Survey

David Bekaert

NASA Jet Propulsion Laboratory, 

California Institute of Technology

William Brooks

NOAA National Ocean Service

Michael Craghan

U.S. Environmental Protection Agency

Gregory Dusek

NOAA National Ocean Service

Thomas Frederikse

NASA Jet Propulsion Laboratory

California Institute of Technology

Gregory Garner

Rutgers University

Ayesha S. Genz

University of Hawai‘i at Mānoa, Cooperative 

Institute for Marine and Atmospheric Research

John P. Krasting

NOAA Geophysical Fluid Dynamics Laboratory

Eric Larour

NASA Jet Propulsion Laboratory,

California Institute of Technology 

Doug Marcy

NOAA National Ocean Service

John J. Marra

NOAA National Centers for Environmental 

Information

Jayantha Obeysekera

Florida International University

Mark Osler

NOAA National Ocean Service

Matthew Pendleton

Lynker

Daniel Roman

NOAA National Ocean Service

Lauren Schmied

FEMA Risk Management Directorate

Will Veatch

U.S. Army Corps of Engineers

Kathleen D. White

U.S. Department of Defense

Casey Zuzak

FEMA Risk Management Directorate
Global and Regional Sea Level Rise Scenarios for the United States | iv

Table of Contents

List of Figures............................................................................................................................................................vi

List of Tables...............................................................................................................................................................x

Executive Summary................................................................................................................................................. xii

Section 1: Introduction ...............................................................................................................................................1

Section 2: Future Mean Sea Level: Scenarios and Observation-Based Assessments.................................6

2.1. Overview of Regional and Global Sea Level Rise........................................................................................6

2.2. Updates from Sweet et al. (2017) ....................................................................................................................9

2.2.1 Inclusion of Near-Term Time Period (2020–2050)...................................................................................9

2.2.2 GMSL Scenario Divergence and Tracking .................................................................................................9

Box 2.1: Uncertainties.......................................................................................................................................... 10

2.2.3 Updates to the 2017 Sea Level Scenarios..............................................................................................11

2.2.4 Observation-Based Extrapolations .........................................................................................................12

2.3. Near-Term Sea Level Change (2020–2050) .............................................................................................13

2.4. Long-Term Sea Level Change (2050–2150) .............................................................................................20

2.5. Scenario Divergence and Tracking ............................................................................................................. 24

Section 3: Extreme Water Levels and Changing Coastal Flood Exposure .................................................. 28

3.1. Overview of Extreme Water Levels and Coastal Flooding .....................................................................28

3.2. Regional Frequency Analysis of Tide-Gauge Data................................................................................... 31

3.3. Average Event Frequencies of Extreme Water Levels ........................................................................... 32

3.4. Methods to Localize the Gridded Extreme Water Level Event Probabilities ................................... 35

3.5. The Changing Nature of Coastal Flood Exposure .................................................................................37

Box 3.1: Wave Contributions to Extreme Water Levels.................................................................................41

Section 4: Use Cases ............................................................................................................................................. 43

4.1. Mapping of NOAA High Tide Flood Thresholds and Flood Frequencies........................................... 43

4.2. Application of Scenarios, Observation-Based Extrapolations, and Extreme Water Levels .......... 45

4.3. Growing Risk to Combined Storm and Wastewater Systems from Sea Level Rise ........................ 53

4.4. Use of InSAR Technology for Determining Regional Vertical Land Motion and Its Suitability for 

Computing Long-Term Sea Level Rise Projections ..................................................................................55

Section 5: Conclusions ..........................................................................................................................................60

Section 6: Acknowledgments .............................................................................................................................. 63

Section 7: References ............................................................................................................................................ 64
Global and Regional Sea Level Rise Scenarios for the United States | v

Appendix ...................................................................................................................................................................74

Section A1: Tables and Figures.........................................................................................................................74

Section A2: Methods Appendix: Extreme Water Levels and Alaska Coastal Flood Height................86

A2.1: Data and Regional Frequency Analysis....................................................................................................86

A2.2: Gridded (Regional) Extreme Water Level Probabilities........................................................................88

A2.3: Localized Extreme Water Level Probabilities......................................................................................88

A2.3.1: Local Index Estimates from Short-Term Installations..........................................................................89

A2.3.2: Obtaining a Local Index from Tide Range Information .....................................................................91

A2.3.3: Uncertainties Using Alternative Methods to Estimate EWLlocal Probabilities .............................93

A2.3.4: Adjusting Local Extreme Water Level Probabilities to Time Periods............................................93

A2.4: Alaska Coastal Flood Heights................................................................................................................93

Section 8: Acronyms .............................................................................................................................................. 95
Global and Regional Sea Level Rise Scenarios for the United States | vi

List of Figures

Figure 1.1: ................................................................................................................................................................................................... 1

Schematic (not to scale) showing physical factors affecting coastal flood exposure. Due to the clear and strong 

relative sea level rise signal (i.e., combination of sea level rise and sinking lands), the probability of flooding and 

impacts are increasing along most U.S. coastlines.

Figure 1.2: ................................................................................................................................................................................................. 2

a) Observed annual global mean sea level (GMSL) change from global tide gauges (blue line), along with the 

sum (orange line) of contributions from thermal expansion (thermosteric) and four distinct water-mass-driven 

increases in GMSL. b) GMSL change (blue line) as shown in a) with the annual average relative sea level change 

measured by tide gauges around the contiguous United States (black line; with a linear regression estimate of 

28 cm of sea level rise from 1920 to 2020). (Adaptation of Frederikse et al., 2020).

Figure 1.3: ..................................................................................................................................................................................................3

a) Annual probability density and b) annual expected exceedances for daily highest water levels relative to the 

1983–2001 mean higher high water (MHHW) tidal datum showing increases in NOAA minor, moderate, and major 

high tide flooding (HTF) probabilities/frequencies due to relative sea level (RSL) rise at the NOAA tide gauge in 

Charleston, South Carolina. 

Figure 2.1................................................................................................................................................................................................... 8

Regional sea level linear rates of rise (mm/year) from satellite altimetry over three different time periods: (a) 

1993–2006, (b) 2007–2020, and (c) 1993–2020. Linear rates of change of relative sea level (ocean and land 

height changes) from tide gauges over the same time period are also shown (circles).

Figure 2.2: ...............................................................................................................................................................................................14

Observation-based extrapolations using tide-gauge data and five Scenarios, in meters, for a) global mean sea 

level and b) relative sea levels for the contiguous United States from 2020 to 2050 relative to a baseline of 2000. 

Median values are shown by the solid lines, while the shaded regions represent the likely ranges for the observation-based extrapolations and each scenario. Altimetry data (1993–2020) and tide-gauge data (1970–2020) are 

overlaid for reference. 

Figure 2.3: ...............................................................................................................................................................................................18

Observation-based extrapolations and five regionalized global mean sea level scenario projections, in meters, of 

relative sea levels for eight coastal regions around the United States from 2020 to 2050 relative to a baseline of 

2000. Median values are shown by the solid lines, while the shaded regions represent the likely ranges for the 

observation-based extrapolations and each scenario. Tide-gauge data (1970 to 2020) are overlaid for reference, 

along with satellite altimetry observations, which do not include contributions from vertical land motion.

Figure 2.4: ..............................................................................................................................................................................................20

Relative sea level rise, in meters, in 2050 for the a) Intermediate-Low and b) Intermediate-High scenarios relative 

to the year 2000.

Figure 2.5: ..............................................................................................................................................................................................24

Regional deviations of relative sea level from the global mean sea level (GMSL; in meters) value for each scenario 

in 2100. To obtain the regional projection in 2100 for each scenario, the mapped values must be added to the 

GMSL value for the associated scenario.

Figure 2.6: ..............................................................................................................................................................................................25

Divergence of global mean sea level (GMSL) trajectory and scenarios. The time series shows the observation-based GMSL trajectory and the five GMSL scenarios from 2000 to 2100. The dots denote where each scenario significantly (2 sigma) deviates from the a) observation-based trajectory and from the b) Intermediate scenario.
Global and Regional Sea Level Rise Scenarios for the United States | vii

Figure 2.7:...............................................................................................................................................................................................27

Proportions of the contributions from different IPCC AR6 sea level trajectories to each of the five global mean 

sea level (GMSL) rise scenarios used in this report: Low, Intermediate-Low, Intermediate, Intermediate-High, and 

High. The IPCC AR6 trajectories are Low Emissions; Low Emissions, LC (where LC indicates inclusion of low-confidence ice-sheet processes); Intermediate Emissions; Intermediate Emissions, LC; High Emissions; and High 

Emissions LC. The emissions pathways associated with the IPCC AR6 trajectories are as follows: Low Emissions 

= Shared Socioeconomic Pathway (SSP) 1-1.9 or SSP1-2.6; Intermediate Emissions = SSP 2-4.5; High Emissions = 

SSP3-7.0 or SSP5-8.5. Shifts between different GMSL rise scenarios approximately reflect the relative odds of being close to a given scenario under different emissions pathways; e.g., the Low scenario is much more plausible 

under a low emissions pathway, while Intermediate and higher scenarios are much more likely to be associated 

with high emissions pathways, as well as with low-confidence ice-sheet processes. 

Figure 3.1:................................................................................................................................................................................................29

National median rate of minor high tide flooding and relative sea level, in meters, from 98 NOAA tide gauges 

along U.S. coastlines outside of Alaska used to monitor and track flood-frequency changes (from Sweet et al., 

2021). Relative sea levels reference the lowest annual (1925) level.

Figure 3.2: ..............................................................................................................................................................................................32

Regional Frequency Analysis 1-degree grids and local index values (u) relative to local mean higher high water 

tidal datum at the NOAA tide gauges used in this study.

Figure 3.3:...............................................................................................................................................................................................33

a) Empirical probability densities of hourly water levels and their daily maxima measured by the NOAA tide gauge

at The Battery (New York City), as well as the tidal datums of mean lower low water (MLLW), great diurnal tide

range (GT), local high tide flood (HTF) heights, and the local index (u) used to localize the RFA-gridded EWL for

this location (see Figure A2.2f). All values are referenced to the mean higher high water (MHHW) tidal datum and

shown in b) as a return interval curve with the 95% confidence interval (2.5% and 97.5% levels) normalized to year

2020 RSLs.

Figure 3.4: ..............................................................................................................................................................................................34

Current (circa 2020 relative sea levels) EWLlocal that a) occur annually on average and b) have a 0.01-year average event frequency. Note: the scales in the two figures are not the same, and to be useful for decision-making, 

a conversion to land-based heights (e.g., NAVD88) should be made.

Figure 3.5: ..............................................................................................................................................................................................35

Comparison between (a–c) this study’s EWLlocal to those of NOAA (Zervas, 2013) based on a GEV fit of annual 

highest water levels and to (d–f) the stillwater (storm surge, tides, and wave set-up) components of FEMA used 

in their Flood Insurance Study at the 0.01-year, 0.1-year, and 0.5-year average event frequency levels.

Figure 3.6: .............................................................................................................................................................................................. 37

a) Map showing active NOAA tide gauges indicating Grand Bay, Mississippi, which has about 4–5 years of hourly

data, b) tide range to local index (u) regression relative to the 1983–2001 tidal datum epoch with fit equation,

goodness of fit (R2), and associated root mean square error (RMSE) for the surrounding region, c) RMSE for

estimates of u based on 1–19 years of consecutive data over the 2001–2019 period based on the regional tide

gauges for the surrounding region; and d) a 2020 EWLlocal return level curve for Grand Bay using a local index

(u) from tide range regression. Note: to be useful for decision-making, a conversion to land-based heights (e.g.,

NAVD88) should be made.

Figure 3.7:...............................................................................................................................................................................................38

NOAA minor (red layer: land between mean higher high water [MHHW] and minor high tide flood [HTF] height 

above MHHW), moderate (orange layer), and major (yellow layer) HTF maps showing a regional layered map with 

individual layer panes to the right for a) Charleston, South Carolina, and b) West Palm Beach, Florida. MHHW for 

1983–2001 is the shoreline edge. Note: to be useful for decision-making, a conversion to land-based heights 

(e.g., NAVD88) should be made.
Global and Regional Sea Level Rise Scenarios for the United States | viii

Figure 3.8: ..............................................................................................................................................................................................39

Average event frequencies in 2020 of a) minor high tide flooding (HTF); b) number of “days” (as compared to 

“events”) of HTF estimated in NOAA’s annual outlook (Sweet et al., 2021) and regression between events and 

days; c) average event frequencies in 2020 of moderate HTF; and d) average event frequencies in 2020 of major 

HTF. Flood height-severity definitions are from NOAA (Sweet et al., 2018) and, specifically for Alaska locations, 

from Sweet et al. (2020b).

Figure 3.9: ..............................................................................................................................................................................................40

Coastal high tide flooding (HTF) frequencies projected at 2050 applying the sea level scenario that upper-bounds 

the regional observation-based extrapolations for NOAA a) minor, b) moderate, and c) major HTFs

Figure Box 3.1: .......................................................................................................................................................................................42

Water level contribution due to a) wave set-up and b) wave swash; c) percent contribution of wave-driven water 

levels (i.e., wave run up = wave set-up and swash) relative to all components: tide, storm surge, and waves; and 

d) percent contribution of wave set-up relative to the sum of tide, storm surge, and wave set-up based on model

reanalysis of Vitousek et al. (2017).

Figure 4.1:................................................................................................................................................................................................45

Maps of the NOAA minor, moderate, and major high tide flooding layers for a) Charleston, South Carolina, and 

b) West Palm Beach, Florida (as in Figure 3.7 but providing average event frequencies for each layer). Note: the

shoreline on these maps is mean higher high water, but to be useful for decision-making, a conversion to landbased heights (e.g., NAVD88) should be made.

Figure 4.2: ..............................................................................................................................................................................................46

Tide gauges selected for the application of sea level scenarios and extreme water level methods.

Figure 4.3: .............................................................................................................................................................................................. 47

a) RSL projections for the scenarios providing the upper bound to observation-based extrapolations to 2060 for

the selected tide gauges. The corresponding scenario for each tide gauge is shown in parentheses in the legend. b) RFA-based EWL (see Section 3) return level curves relative to the 1983–2001 MHHW tidal datum. Notes:

(1) to be useful for decision-making, a conversion to land-based heights (e.g., geodetic datum such as NAVD88)

should be made. (2) Average event frequency (x-axis label) is the reciprocal of average recurrence interval, which

is also known as return period.

Figure 4.4: ..............................................................................................................................................................................................48

Recurrent flood frequency estimates for a) Sewells Point (Norfolk), Virginia, and b) Galveston Pier 21, Texas. For 

both, the relative sea level projection for the scenarios and the return level are the same as in Table 4.1. Note: to 

be useful for decision-making, a conversion of the return level to land-based heights (e.g., geodetic datum such 

as NAVD88) should be made.

Figure 4.5: ..............................................................................................................................................................................................50

Conceptual illustration of increasing exceedance probability (hence decreasing average recurrence interval) that 

assumes that the location parameter is a function of the magnitude of the relative sea level rise.

Figure 4.6: ...............................................................................................................................................................................................51

a) Average recurrence interval (due to rising RSL) curves (T versus T_0) at each tide gauge using the selected

scenario’s RSL projection (see Table 4.1). b) Risk curves as a function of design life: stationary (black curve), actual

risk resulting from incorporating the site’s RSL scenario projection (red curve), and risk curve for a specific risk

(blue curve).

Figure 4.7:...............................................................................................................................................................................................55

Location of combined stormwater and sewer system outfalls that are likely draining regions exposed to HTF 

within the Camden, New Jersey, region, with the minor (red: MHHW to 0.58 m [1.9 feet] above MHHW), moderate 

(orange: MHHW to 0.86 m [2.8 feet] above MHHW), and major (yellow: MHHW to 1.25 m [4.1 feet] above MHHW) 

HTF layers stacked in the enlarged map and individual layers mapped to the right. Note: heights are relative 

to the 1983–2001 tidal epoch, and to be useful for decision-making, a conversion to land-based heights (e.g., 

NAVD88) should be made.
Global and Regional Sea Level Rise Scenarios for the United States | ix

Figure 4.8: ..............................................................................................................................................................................................57

Comparison of vertical land motion (VLM) rate estimates (mm/year) from a) the scenario-based framework used 

in this report, and b) GPS-imaging estimates from Hammond et al. (2021). c) The difference between GPS-derived 

rates and scenario-derived rates and d) a comparison of the VLM estimates at the U.S. tide-gauge locations are 

also shown. Negative values of VLM reflect subsidence, while positive values reflect uplift.

Figure 4.9: ..............................................................................................................................................................................................58

Map showing VLM rates (mm/year) for the Hampton Roads region displayed on top of satellite imagery. Higher 

rates of subsidence are indicated by darker orange colors. Of particular interest is the range of rates in such a 

small region (e.g., on the order of up to 5 mm/year difference in places). Based on Buzzanga et al. (2020).

Figure A1.1: ............................................................................................................................................................................................. 74

Region definitions for observation-based extrapolations and scenarios in Section 2. These regions are used both 

to group tide gauges and also to generate regional averages for the gridded scenarios. A bathymetry mask is 

used to define the regions for the gridded scenarios.

Figure A1.2: ............................................................................................................................................................................................ 75

Shown for each tide gauge record with at least 30 years of record length between 1970 and 2020 are a) range, 

in meters, between median projection of Low and High Scenarios in 2050, and b) difference, in meters, between 

median observation-based extrapolation and Intermediate scenario in 2050.

Figure A2.1:.............................................................................................................................................................................................86

NOAA tide gauges used in the regional frequency analysis to generate extreme water level probabilities for 

U.S coastlines.

Figure A2.2: ...........................................................................................................................................................................................87

Example of data from grid number 46415 showing exceedances above each local index (u) relative to the 1983–

2001 mean higher high water (MHHW) tidal datum at a) Kings Point, New York; b) The Battery, New York; c) Bergen Point, New York; and d) Sandy Hook, New Jersey, which are e) aggregated into a single dataset and f) fit by 

a Generalized Pareto Distribution to form a return level interval curve for the grid.

Figure A2.3: ...........................................................................................................................................................................................89

Additional tide-gauge data available from NOAA that can be used to localize the 1-degree gridded set of regional frequency analysis-based extreme water level probabilities. 

Figure A2.4: ...........................................................................................................................................................................................90

Root mean square error for regional estimates of flood indices (u) based on 1–19 years of consecutive data over 

the 2001–2019 period, based on regional sets of tide gauges used in this study. Note: these regions are not the 

same as those shown in Figure A1.1 and used to describe results in Sections 2 and 3 of the report. 

Figure A2.5: ...........................................................................................................................................................................................92

Tide range to local index (u) regressions with equations, goodness of fit (R2), and root mean squared error (RMSE) 

shown by regions. Note: all local indices (u) are relative to the 1983–2001 tidal datum epoch. In the equations, y 

represents the local index (u) and x represents tide range. 

Figure A2.6: ...........................................................................................................................................................................................94

a) Quadratic regression of U.S. West Coast minor flood heights of NOAA’s National Weather Service, following 

methods of Sweet et al. (2020b), to obtain a minor HTF definition for Alaska’s coastline. The NOAA flood heights 

for b) minor, c) moderate, and d) major HTF are shown relative to mean higher high water.
Global and Regional Sea Level Rise Scenarios for the United States | x

List of Tables

Table 2.1:...................................................................................................................................................................................................15

Observation-based extrapolations and five scenarios, in meters, for global mean sea level and relative sea level for the contiguous United States from 2020 to 2050 relative to a baseline of 2000. Median [likely ranges] 

are shown.

Table 2.2: .................................................................................................................................................................................................19

Observation-based extrapolation and regionalized global mean sea level scenario–based estimates, in meters, 

of relative sea level in 2050 relative to a baseline of 2000 for eight coastal regions of the United States. Median 

[likely ranges] are shown. The two scenarios that bound the median observation-based extrapolation are also 

provided for each region and indicated by red dividing lines. In regions where the observation-based extrapolation is the same as a particular scenario, the scenario is indicated in red text and the bounding scenarios can 

be assumed to be the next higher or lower scenario (e.g., the Intermediate bounds the Northeast’s observation-based extrapolation).

Table 2.3: ................................................................................................................................................................................................20

Global mean sea level and contiguous United States scenarios, in meters, relative to a 2000 baseline.

Table 2.4: ................................................................................................................................................................................................22

IPCC warming level–based global mean sea level projections. Global mean surface air temperature anomalies 

are projected for years 2081–2100 relative to the 1850–1900 climatology. Sea level anomalies are relative to a 

2005 baseline (adapted from Fox-Kemper et al., 2021). The probabilities are imprecise probabilities, representing a consensus among all projection methods applied. For imprecise probabilities >50%, all methods agree that 

the probability of the outcome stated is at least that value; for imprecise probabilities <50%, all methods agree 

that the probability of the outcome stated is less than or equal to the value stated.

Table 2.5: ................................................................................................................................................................................................23

Scenarios of relative sea level, in meters, for eight coastal regions of the United States in 2100 and 2150 relative 

to a baseline of 2000. Median values are shown. 

Table 3.1:..................................................................................................................................................................................................30

Physical processes affecting U.S. coastal water levels and their temporal and spatial scale properties (modification of Sweet et al., 2017). Extreme water levels, which, as measured by tide gauges, generally exclude 

high-frequency wave effects, include processes between tsunami and ocean-basin variability and, to a lesser 

extent, low-frequency changes or trends associated with land ice melt/discharge, thermal expansion, and vertical 

land motion.

Table 3.2: .................................................................................................................................................................................................41

Annual average event frequencies for NOAA-defined minor, moderate, and major HTF heights by region that 

were typical (median values) in 1990, under current (circa 2020) sea levels and projected to occur considering 

the upper-bounding scenario of the observations-based extrapolations in 2050 (see Table 2.2).

Table 4.1:..................................................................................................................................................................................................46

Tide-gauge locations, scenarios bounding the observation-based extrapolations, and the extreme value distribution Generalized Pareto Distribution (GPD) model parameters estimated using the regional frequency 

analysis (RFA).

Table 4.2: ................................................................................................................................................................................................49

Summary of design parameters to constrain the average event frequency, N, to 1 per year by 2060 (end-year of 

the design life). The 2005–2060 RSL projections are the local values associated with the scenarios providing 

the upper bound to the regional observation-based extrapolations shown in Table 2.2. Note: to be useful for 

decision-making, a conversion of the return level to land-based heights (e.g., geodetic datum such as NAVD88) 

should be made.
Global and Regional Sea Level Rise Scenarios for the United States | xi

Table 4.3: .................................................................................................................................................................................................51

The parameters of generalized extreme value computed using the peaks-over-threshold Generalized Pareto 

Distribution model (Coles 2001).

Table 4.4: ................................................................................................................................................................................................53

Results of the risk-based design for all tide gauges shown in Figure 4.2. Average recurrence interval (ARI) is listed 

and is the reciprocal of average event frequency. Values in the last column have been rounded to the closest 

5-year interval. Note: to be useful for decision-making, a conversion of the return level to land-based heights

(e.g., geodetic datum such as NAVD88) should be made.

Table A1.1:................................................................................................................................................................................................ 76

Projections methods employed. 

Table A1.2: .............................................................................................................................................................................................. 76

Offsets, in meters, for different time periods and for each region considered in Section 2. These offsets are assessed using the trajectory determined from the available tide-gauge data in each region.

Table A1.3: .............................................................................................................................................................................................. 77

Regional designation, tide gauge information, extreme water level metadata, and high tide flood heights.