Dan Rodricks

Maryland estimate for seawalls against rising tides: $27 billion

Several islands and properties in the lower Chesapeake Bay have been slowly eroding away as sea levels rise.

A third bridge to get more cars and trucks across the Chesapeake Bay, wider highways to move traffic along the Capital Beltway — those might be the ambitions of Maryland’s road-warrior governor, but they are fanciful luxuries compared to what could be the major infrastructure demand facing the state in the decades ahead: Seawalls to protect thousands of homes, businesses and farmlands, from Ocean City to Baltimore, at a cost of more than $27 billion.

And that’s a modest estimate based on moderate sea-level rise, according to a study from a team of engineers and geodata specialists who examined climate-change trends along the U.S. coast.


Ten Chesapeake counties could face the biggest seawall expenses before 2040 — $6.5 billion in Dorchester alone, the report says — and that does not include the costs of adapting or building new stormwater and drinking water systems. It does not include the costs of raising and repairing roads, extinguishing wildfires, replenishing beaches, building community cooling centers and air-conditioned public housing, dealing with droughts or recovering from extreme storms.

The report did not address the option of moving homes and businesses away from areas likely to frequently flood. It focused simply on the construction of seawalls.


The study came from the Institute for Governance and Sustainable Development, a Washington-based organization with an international reach. It focuses on environmental policy and helping governments address the challenges of climate change. The IGSD has partnerships with the United Nations and universities. It claims no corporate affiliations.

The report on the costs of seawalls came out of an IGSD initiative called the Center for Climate Integrity. The report was released June 20, just a day after the Trump administration reversed federal rules designed to reduce planet-warming carbon emissions. Carbon emissions have caused climate change, and climate change is a direct cause of sea-level rise. The University of Maryland Center for Environmental Science predicts that levels around the state could rise anywhere from a foot to seven feet by the end of the century. It depends on how much carbon dioxide the world puts into the atmosphere, and researchers use different carbon-emission scenarios in their studies. Based on current trends, UMCES predicts about 7 inches of rise by 2030 and 1.2 feet by 2050.

Let’s pause here for a word from the National Oceanic and Atmospheric Administration: “Carbon dioxide levels today are higher than at any point in at least the past 800,000 years. In fact, the last time the atmospheric CO2 amounts were this high … temperatures were 3.6 to 5.4 degrees Fahrenheit higher than during the pre-industrial era, and sea level was 50 to 80 feet higher than today. Carbon dioxide concentrations are rising mostly because of the fossil fuels that people are burning for energy. Fossil fuels like coal and oil contain carbon that plants pulled out of the atmosphere through photosynthesis over the span of many millions of years; we are returning that carbon to the atmosphere in just a few hundred years.”

Now back to today’s column: The report from the IGSD says the U.S. faces $400 billion in seawall construction in the next 20 years. Florida, far and away, faces the biggest threats from sea-level rise, and the biggest bill for protective barriers — an estimated $75 billion. Louisiana, North Carolina and Virginia each had costs above $30 billion. Maryland was fifth on the list, with a seawall bill of $27.4 billion. That, the report said, is “a conservative estimate of what it will take to safeguard businesses, homes, roads and entire communities in Maryland from chronic flooding by 2040 under a moderate sea-level-rise scenario.”

The team that conducted the study consisted of mapping and geodata specialists from the University of Colorado and a Colorado-based engineering company that specializes in “climate adaptation,” Resilient Analytics. They ran two different carbon-emissions scenarios to come up with sea-level rise models and factored in one-year storm surges for different parts of the country. “A one-year storm surge is the level to which the coastal water rises in any given year during a typical storm, according to historical sea-level data,” the report notes. “It is an extremely common storm event, as opposed to a 100-year storm surge, which represents a severe event that statistically occurs once every 100 years.”

That’s one of the reasons that the team considers its calculations conservative. “The situation may turn out to be much worse,” researchers say. “Sea levels could easily rise more than the estimates used in the study; they are very unlikely to rise less. And many localities will protect for more damaging storms than the modest one-year storm surge used in this analysis.”

The report gives estimates of seawall costs for the most vulnerable counties and specific communities. For instance, Anne Arundel County would need $1.9 billion, Somerset about $3 billion. Ocean City’s costs would be about $238 million, and Annapolis’ about $195 million. Saving places like Dames Quarter on Deal Island, and the island itself, would cost close to $1 billion. The report puts the price tab for seawall protection for all vulnerable areas of the 1st Congressional District, covering the Eastern Shore and parts of Baltimore, Carroll and Harford counties, at $20 billion. These are extraordinary amounts of money. (The current Maryland state government budget is $46.6 billion.) It’s hard to imagine taxpayers footing the bill. It’s easier to imagine some waterfront communities being abandoned.

The organization behind the study thinks the fossil fuel industry should pay most, if not all, of these costs. The city of Baltimore is among municipalities already on the case. City Solicitor Andre Davis filed a climate liability lawsuit against more than two dozen oil and gas companies last year in an effort to hold them financially responsible for their contributions to climate change. On June 11, a U.S. District judge ruled in the city’s favor, sending the case to be heard in state, rather than federal, court.