individuals’s reactions to sea level rise differ from those of individuals who live inland along Louisiana’s Gulf Coast in areas where the road to the closest grocery store already floods on a typical high tide without any storm in sight. To them, it’s not abstract. It’s the water seeping under the back door in October, the sandbags that are now a permanent feature in garages, and the school system that subtly rearranged the schedule to avoid the twice-weekly flooding on the access road. The NOAA and NASA Sea Level Rise Technical Report quantifies the difficulties these communities are presently facing and predicts that it will occur ten times more frequently than it does now.
The report is based on an average national sea level rise of 10 to 12 inches by 2050. In theory, the figure seems doable, especially for those who live far from the shore and consider sea level rise in terms of far-off worst-case situations. In actuality, this implies that by the middle of the century, every storm surge, severe downpour, and king tide will function from a baseline that is one foot higher than it is now. The 10- to 12-inch national average translates into flooding that occurs more than ten times as frequently as the current baseline because coastal flooding is nonlinear, meaning that a few extra inches of elevation in the water column dramatically expands the area affected and the frequency of damaging events.
Compared to the national average, the regional statistics provide a clearer picture. By 2050, the Gulf Coast, where land subsidence exacerbates ocean rise, would see an increase of 14 to 18 inches, the highest regional rates in the nation. The East Coast faces 10 to 14 inches of above-average rise along the Atlantic seaboard due to AMOC weakening. The additional flooding that storm surges will cause on top of a higher baseline is not taken into account by either of these figures. In major events, hurricane storm surges in the Gulf of Mexico already reach heights of ten to fifteen feet; adding 14 to 18 inches to the starting elevation from which those surges operate expands their inland reach in ways that are not accurately represented by current flood maps, many of which are based on historical data that predates the accelerating rise of recent decades.
The aspect of this that local governments are starting to deal with in really challenging practical terms is the infrastructural consequences. When roadways flood during high tides in September and October, schools in coastal Virginia and Maryland already close. Power plants, natural gas terminals, and substations are among the energy infrastructure located close to sea level that are more vulnerable to saltwater intrusion, which corrodes equipment and interferes with service. During the course of the project, wastewater treatment facilities in South Florida will operate at elevations below high-tide water levels. These effects are not speculative. They are the extension of patterns already apparent to the people in charge of the communities this infrastructure serves as well as the engineers overseeing it.
The $500 billion figure that is attached to this image is an estimate of the total economic damages that the projected flooding levels would cause to coastal communities in the United States by 2050. These damages include property losses, infrastructure replacement costs, disrupted economic activity, and emergency response expenditures. It’s the kind of figure that makes headlines before being lost in the general cacophony of climate economics and failing to elicit the necessary planned reaction. The fact that the costs don’t appear as a single occurrence that necessitates an obvious reaction is part of the issue. They build up through recurrent, small-scale damage to buildings, roads, and systems that, on their own, seem like manageable issues until the pattern of recurrent costs becomes apparent.
The planning tool that federal agencies have developed to assist local governments in converting the projections into site-specific risk information is NOAA’s Sea Level Rise Viewer, a publicly accessible interactive tool that maps projected flooding levels at various rise scenarios for any coastal location in the United States. It is effective for its intended use, which is to show a planning department in Miami or a flood manager in Norfolk what their shoreline would look like in several 2050 scenarios. It is unable to address the financial and political obstacles that make it difficult for towns without the institutional ability, tax base, or state-level backing to finance the extent of infrastructure alteration that the forecasts suggest.
