John Metcalfe was CityLab’s Bay Area bureau chief, covering climate change and the science of cities.
How rising sea levels might overwhelm homes and military bases in the nation's capital.
It's amazing that with a 97 percent scientific consensus on human-caused climate change we still have politicians talking smack about its importance. Will their tune change at all, one wonders, once the flood waters are lapping at the base of the federal government?
This mapping tool can't answer that question, but it does give an indication of what a climate-enraged flood could mean for Washington, D.C. And to believe the folks at Climate Central, the independent group that created it with government data, such an epic dousing is nigh. They say the city will "likely see a record flood before mid-century," meaning one that would measure 8 feet above the high-tide level in the Tidal Basin. Such a deluge could endanger more than 1,000 homes and three military facilities, by their estimation, as well as possibly spreading contamination from many sewage-treatment sites and facilities that deal with hazardous materials.
The map assumes that sea levels will continue to rise as the atmosphere warms up, a result of melting glaciers and the heat-expansion of water. It also takes into account D.C.'s various flood-protection barriers (such as this new one that's supposed to protect Federal Triangle, home of the IRS and the Department of Justice). Should a walloping storm rush through town, bringing waters a foot higher than those of 2003's Hurricane Isabel, Climate Central predicts that flooded areas might include the National Mall, Foggy Bottom, Washington Navy Yard, and much of Southwest D.C.
How often could this happen? With a "medium" rise in sea levels, say the people at Climate Central, there's a one-in-two chance of a record-setting flood (above 7.9 feet) by 2040. In the worst-case scenario for a "highest" sea rise, these biblical-style floods could happen every year by 2100. And, of course, D.C. wouldn't be the only area affected, as the whole coastline is vulnerable to storm surges, they say:
Risks are rising with sea levels in the Delaware, Maryland, and Virginia area as a whole, threatening some 183,000 people, 116,000 homes, $42 billion in property value, and 3,400 miles of roads on land less than 5 feet above local high tide lines, after accounting for potential protection from ridges and levees. Flood threats vary by location, but across 11 study sites in the region and under a mid-range sea level rise scenario, the average risk for a local flood topping 5 feet by mid-century is 55 percent, according to Climate Central’s analysis.