Technical Bulletins on Climate Adaptation in Civil and Environmental Engineering
ASCE Committee on Adaptation to a Changing Climate
Climate Adaptation Engineering Bulletin No. 1 Using Federal Sea Level Rise Projections in Engineering Practice
The US Interagency Task Force for Sea Level Rise recently published the 2022 Sea Level Rise Technical Report, which provides updated projections of sea level rise through the year 2100 for coastal locations throughout the United States and its territories. The report, a joint product of several key Federal agencies including the NOAA, NASA, EPA, the U.S. Army Corps of Engineers and FEMA, provides an update to projections prepared in 2017, using the most up to date observations and models.
Sea levels have been rising globally since at least the late 1800s, but the rate of rise from 1901-2018 is easily the highest it has been in the last 3000 years. An accelerating trend has been especially noticeable since the 1970s, primarily driven by melting of the Greenland and Antarctic ice sheets and thermal expansion of ocean water due to near surface increases in water temperature. Sea level rise will have a continuing substantial impact on the planning and design of civil engineering projects in coastal areas.
The Sea Level Rise Technical Report, available at this link (2022 Sea Level Rise Technical Report (noaa.gov)), discusses the purpose and methodologies used in making the projections, and provides a variety of information resources for each coastal area in the
United States and its territories, including data downloads and a Sea Level Rise Viewer, available at this link (Sea Level Rise and Coastal Flooding Impacts (noaa.gov)). The viewer is user friendly and allows the user to click on any local data point to view 2017 and updated 2022 mean projections of sea level rise for various future global emissions scenarios in ten-year increments from 2030 through 2100 and to view potential impact areas in 1/2 foot increments. To further support the use of the Sea Level Rise Technical Report by local communities and decision makers, NOAA released an application guide (Application Guide for the 2022 Sea Level Rise Technical Report (noaa.gov)).
The increase in Mean Sea Level (MSL) is projected to increase by 2050 typically about 13-20 inches on the east coast, 15-23 inches on the gulf coast, and 4-13 inches on the west coast. Total 2080 sea level rise increases are projected to be typically 3-3.8 feet on the east coast, 3-5 feet on the gulf coast and 2.5-3 feet on the west coast as the rate of sea level rise is projected to accelerate later in this century. These are increases from Year 2000 levels. These ranges reflect the full range of combined greenhouse gas emission and ice melting uncertainties evaluated.
The table below presents projected sea level rise through 2050 and 2080 taken from the Sea Level Rise Viewer assuming the “intermediate high” scenario for selected coastal locations in the United States.
Table 1. Increase in Mean Sea Level from Year 2000 Levels due to Sea Level Rise, NOAA Sea Level Rise Viewer*
Coastal Location SLR, 2050, feet SLR 2080, feet
Portland, ME 1.31 3.02
New York City, NY 1.51 3.38
Charleston, SC 1.48 3.48
Miami, FL 1.31 3.38
St. Petersburg, FL 1.38 3.44
Pensacola, FL 1.31 3.28
Eugene Island, LA 2.49 5.25
Galveston, TX 1.97 4.40
San Diego, CA 1.05 3.12
Los Angeles, CA 0.85 2.79
San Francisco, CA 1.02 3.02
Seattle, WA 0.95 2.72
Honolulu, HI 1.21 3.74
* ”Intermediate High” Scenario
The scenario assumptions provide a range of uncertainty to each of these numerical projections. As an example, for the first location in the table above, Portland, ME, the variation in projected sea level rise from the “intermediate low” to the “high” scenario provides a projected range of 1.0 to 1.4 feet by 2050, and 1.6 to 3.8 feet in 2080. For any given location, civil engineers may need to refer to the Sea Level Rise Viewer and consider the design and service life for a given project and the full range of projections to assist them and their clients in making informed risk management decisions regarding design resilience.
Additional and varying projections of sea level rise may be available from State Coastal Zone Management agencies and/or local or regional governmental agencies.
The projection resources referenced herein can be used to add to the Mean Higher High Water Level (MHHWL) or the Highest Astronomical Tide (HAT) to provide estimates of future inundation levels from tidal sources (i.e. “sunny day flooding”). Sea level rise as reported by increases in mean sea level does not tell the whole story regarding coastal flooding risk. The 2022 sea level rise report cautions that the information referenced is a screening tool and does not include the significant additional impacts to water levels effected by storm surge, wind and wave run-up. Each of those factors vary considerably both locally and regionally and have a significant impact on the planning and design of civil engineering projects. There is generally less information currently available projecting future impacts of these factors, but work is underway, to be summarized in subsequent articles.
Technical Bulletins on Climate Change in Civil and Environmental Engineering are prepared by the American Society of Civil Engineers Committee on Adaptation to Climate Change, Dan Walker, Ph.D., and Craig Musselman, P.E., editors. NOTE: These Engineering Bulletins are intended to alert the reader to emerging topics related to climate change in engineering practice and are not intended to act as a substitute for any sources cited herein.