Planning for Annapolis Sea Level Rise and Future Extreme Water Levels

U.S. Naval Academy Sea Level Rise Advisory Council

31 October 2017

CAPT Emil Petruncio, USN (Ret.), PhD Associate Professor Gina Henderson

Photo Credit: https://marinas.com

https://www.forbes.com/pictures/eidm45hdm/united-states-naval-academy/#de0be7ef6918 Photo: Forbes Images

The U.S. Naval Academy is a 338 acre National Historic Landmark.

The buildings, monuments, and traditions of the U.S. Naval Academy preserve and promote the core values of the Navy and Marine Corps: Honor, Courage, and Commitment.

Naval Academy Sea Level Rise Advisory Council Constituted in July 2015 by direction of the Superintendent of the Naval Academy

• Mission: Develop a Sea Level Adaptation Plan for the Superintendent on matters pertaining to flooding due to sea level rise and severe weather events in the Annapolis area.

• This plan, developed in coordination with the City of Annapolis, the State of Maryland and key federal agencies, will suggest a path forward for planning for the impacts of sea level rise on the Naval Academy through 2100.

• Specific focus: impacts to operational requirements of the Naval Academy, including the USNA lower yard, upper yard and the federal property on North Severn.

Annapolis Hourly Sea Level Data for 1933 and 2003 Referenced to Mean Lower Low Water

Both years featured major flooding events due to storm surge, but average sea level in 2003 was 0.75 feet (9 inches) higher than in 1933, resulting in broader areal flooding for extreme events and much more frequent occurrences of minor flooding. According to NOAA (Sweet and Park, 2014), the number of nuisance flood days for Annapolis has increased from 3 per year during 1956-60 to 34 per year during 2006-10.

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1933 Avg = 0.11 ft

Hurricane Isabel Chesapeake – Potomac Hurricane

Dashed line indicates level of minor flooding at Annapolis City Dock (2.38 ft above MLLW)

Cumulative Hours of Flooding minor moderate 1933: 26 18 2003: 130 21

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Nuisance Flooding at Annapolis City Dock (NWS “Minor” Threshold = MLLW + 2.38 ft)

MLLW

Nuisance flooding events in Annapolis have increased significantly in the past several decades, and are more frequent during Mid-Spring to Mid-Autumn due to warmer surface waters and thermal expansion.

Annapolis Hourly Water Levels 15 April – 15 October 2014

Nuisance Flooding at USNA (MLLW + 2.75 ft)

MSL

Recent Sea Level Studies

• 2012 NRC Report on MSLR Processes, NOAA Sea Level Rise Scenarios for National Climate Assessment (NCA)

• 2013 IPCC Assessment Report 5 (AR5), MD Update of 2008 Assessment, Updated USACE Guidance

• 2014 National Climate Assessment

• 2016 DoD-led, Multi-Agency Report on Regional Scenarios (Hall et al., 2016),

UCS Report on 18 Military Installations,

Military Expert Panel Report on SLR

• 2017 NOAA Global and Regional SLR Scenarios for the U.S.

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Relative Sea Level Rise Scenarios for Annapolis from Hall et al. (2016) and Sweet et al. (2017)

with Annapolis Monthly Mean Sea Level Data for 1930-2016

The six Global Mean Sea Level (GMSL) scenarios in Sweet et al., 2017, identified by the height in meters in 2100 relative to MSL in 2000, span the range of scientifically plausible sea level rise scenarios. The shaded regions represent a central 80% probability range for each scenario. These curves have been adjusted to depict MSL relative to 1992. The five scenarios described in Hall et al., 2016 correspond to GMSL of 2.0m, 1.5m, 1.0m, 0.5m, and 0.2m relative to MSL in 1992, and are indicated by thick black lines.

Intermediate Low (0.5m)

Intermediate (1.0m)

Intermediate High (1.5m)

High (2.0m)

Extreme (2.5m)

Low (0.3m)

High Emission Scenario with Max Contribution from Ice Sheets

Low Emissions; Major Carbon Cuts and Carbon Removal

Moderate to High Emissions

Graphic by E.T. Petruncio

Graphics courtesy of Ocean Exploration Trust and Liu et al., 2004, Holocene development of the Yellow River’s subaqueous delta, North Yellow Sea. Marine Geology, 209(1-4): 45-67

During the Holocene Epoch, the rate of sea level rise has varied between still stands and periods of rapid rise (several meters per century), resulting in submerged marine terraces. The rapid rates of sea level rise indicate that ice shelves can break up rapidly. http://ocean.si.edu/sea-level-rise

MWP = Melt Water Pulse

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Hall et al. (2016) Annapolis Sea Level Rise Scenarios Referenced to MSL for 1983-2001 (MSL = 0 in 1992)

Ramsay Rd, McNair Rd, City Dock

Waffle Lot

Mid Store Lot, NW End Holloway Rd

Isabel

An average high tide (Mean High Water) will add 0.47 ft to these values twice daily.

For short range forecasts (2035 and earlier), interannual variability (+/- 4 inches) may be more significant than changes due to long term sea level rise.

Hospital Point, Dewey Field, Gate 1

Note: Increases in MSL may not be as smooth as depicted, especially for highest scenario (when most SLR would occur beyond 2070)

Severn River College Creek

Spa Creek

Graphic courtesy of Climate Central http://ss2.climatecentral.org/

Datum: Mean Higher High Water (.71 feet above MSL)

4 ft Above Mean Higher High Water (4.71 feet above MSL) (Mid Store Lot, Brownson Rd, 8th Wing Lot, Gate 1 area)

2.5m: 2058 2.0m: 2064 1.5m: 2075 1.0m: 2096

Dates at which MSL reaches this level for various scenarios

https://www.wunderground.com/wximage/awalex/0/

Hurricane Isabel 19 Sep 2003 4 hours (5 inches) prior to peak water level

Extreme Events

Inundation of the U.S. Naval Academy after Hurricane Isabel

Graphic courtesy of Climate Central http://ss2.climatecentral.org/

Datum: Mean Higher High Water (.71 feet above MSL)

6 ft Above Mean Higher High Water (6.71 feet above MSL) (Hurricane Isabel)

2.5m: 2073 2.0m: 2082 1.5m: 2096

Date at which MSL reaches this level for the highest scenario

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1% / 100 year

Isabel

Hospital Pt, Dewey Fld, Gate 1

Annapolis Historical Sea Level, Scenario for a 1.0m rise in Global Mean Sea Level and Extreme Water Levels based on Hall et al., 2016

Adjustment for MHHW

Ramsay Rd, McNair Rd, City Dock

Waffle Lot

Midstore Lot

Flooding Event 2035 2065 2100

20% / 5 Year 5.0 5.6 8.1

5% / 20 Year 5.9 6.5 9.0

2% / 50 Year 6.9 7.5 10.0

1% /100 Year 7.9 8.5 11.0

Extreme Water Levels (ft) for 1.0m GMSL Scenario (Hall et al., 2016)

• Uncertainties in future Sea Level Rise (SLR) include climate forcings (cloud cover, aerosols, etc.), physical system response (Antarctic ice shelves and glaciers, etc.), and human behavior (future greenhouse gas emissions). We should deal with these uncertainties by considering a range of SLR scenarios and risk tolerances for various projects.

• Range of plausible SLR scenarios for Annapolis, relative to Mean Sea Level (MSL) (MSL = 0 in 1992):

Under a conservative SLR scenario (1m / 3.28 ft rise in Global MSL by 2100), nuisance flooding at USNA will occur daily during the summer months beginning around 2050-2065.

• Flooding due to storm surge will be exacerbated by SLR. Most scenarios considered by Hall et al. (2016) show Hurricane Isabel-like water levels becoming a 1 in 20 year event by 2065 and a 1 in 5 year event by the end of the century. These projections are based on historical storm statistics, and assume no changes in storm frequency or intensity.

Hall et al. (2016) Sweet et al. (2017)

2050 0.7 – 2.7 ft 0.6 – 3.6 ft

2100 1.4 – 8.3 ft 0.9 – 11.7 ft

Summary

Diving Deeper

The Northern Channel Islands were connected during the last glacial maximum, when sea level was approximately 120m lower. As sea level rose, wave action shaped marine terraces.

San Miguel

Santa Rosa

Santa Cruz

Anacapa Marine Terraces

Comparison of Mean Sea Level Trend in Annapolis Tide Gauge Data to Highest and Lowest Scenarios in Hall et al. (2016)

The lower bound for sea level rise scenarios should be based on historical trends dating back at least 50 years, as shorter record lengths (such as satellite altimetry measurements) may be affected by interannual / decadal variability.

A plausible range of sea level rise in Annapolis by 2050 is from 0.2 m (0.7 ft) to 0.8m (2.6 ft), relative to Mean Sea Level for the current tidal epoch (1983-2001) (Hall et al., 2016)

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As of 2015, the rate of sea level rise in Annapolis was 3.53 +/- 0.21 mm/yr

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0.2m (0.7 ft)

0.8m (2.6 ft)

https://www.washingtonpost.com/news/energy-environment/wp/2017/10/26/new-science-suggests-the-ocean-could-rise-more-and-faster-than-we-thought/?utm_term=.7c852e09078f

Based on Figure 5 from Alexander Nauels et al 2017 Environ. Res. Lett. 12 114002 doi:10.1088/1748-9326/aa92b6

Scenario 2035 2065 2100

Lowest 4.3 4.3 5.1

Low 4.3 5.0 6.0

Medium 5.0 5.6 8.1

High 5.0 6.3 9.7

Highest 5.3 7.3 12.0

Scenario 2035 2065 2100

Lowest 5.2 5.2 6.0

Low 5.2 5.9 6.9

Medium 5.9 6.5 9.0

High 5.9 7.2 10.6

Highest 6.2 8.2 12.9

Scenario 2035 2065 2100

Lowest 6.2 6.2 7.0

Low 6.2 6.9 7.9

Medium 6.9 7.5 10.0

High 6.9 8.2 11.6

Highest 7.2 9.2 13.9

Scenario 2035 2065 2100

Lowest 7.2 7.2 8.0

Low 7.2 7.9 8.9

Medium 7.9 8.5 11.0

High 7.9 9.2 12.6

Highest 8.2 10.2 14.9

Combined Sea Level Rise and Extreme Water Level Values (Hall et al., 2016) Base Unit: Feet, Referenced to Mean Sea Level (add 0.05 for NAVD88)

These projections assume stationarity of historical storm statistics

20% / 5 Year Event 5% / 20 Year Event

2% / 50 Year Event 1% / 100 Year Event