Governments Plan for Development of Land Vulnerable to Rising Sea Level: District of Columbia
James G. Titus 2010. "District of Columbia". In The Likelihood of Shore Protection along the Atlantic Coast of the United States. Edited by James G. Titus and Daniel Hudgens. Report to the U.S. Environmental Protection Agency.
The summary is on this page. You can also download a printer quality version of this District of Columbia sea level rise planning study (pdf 1 MB, 36 pp).
As with Baltimore, New York, and most coastal cities, the primary question regarding the District's response to sea level rise is not whether these valuable lands will be protected, but how. Because most of the low-lying areas are lands reclaimed from the creeks or rivers through dredge-and-fill operations, a gradual elevation of low-lying areas would seem most probable, with shoreline armoring to prevent high grounds from eroding. Flood-prone areas such as K Street may continue to mitigate flooding through the use of structural solutions such as tide gates and check valves. This study does not, however, attempt to map the particular shore-protection technique that might be expected.
The summary map shows our assessment of the likelihood of shore protection for Washington, D.C. and adjacent areas of Maryland and Virginia. Table 1 quantifies the area of low land for each of the shore protection categories. Table 2 quantifies the length of the Ditrict's shoreline by likelihood of shore protection.
District planners generally expect the entire Potomac River shoreline to be protected. As the south end, the Blue Plains Sewage Treatment Plant, Naval Research Laboratory, Bolling Air Force Base, and the U.S. Naval Station are already armored. East Potomac Park is also armored, having been created from a dredge-and-fill operation; so to give this area up to a rising river would require reversing decisions made in the 1870s and constitute a return to the shorelines depicted in Pierre L'Enfant's original conception of the city (Figure 1). Allowing rising sea level to inundate filled creeks and canals where office buildings, museums, and the National Mall now sit would be even more implausible. From Georgetown to the Lincoln Memorial the shore is already armored, to prevent erosion of Rock Creek Parkway; a dike protects low-lying areas between the Lincoln Memorial and the White House from flooding. With the exception of a few boat launching areas, Georgetown is also armored (Photo 3). Therefore, the draft shore protection map shows the entire Potomac shore from Georgetown to the Maryland line as almost certain to be protected (brown).
The National Park Service owns the Potomac River shoreline from Georgetown to the head of tide at Little Falls near Chain Bridge. The historic Chesapeake and Ohio Canal parallels the river anywhere from 100 to 1000 feet from the shore. Because preserving the canal and the towpath is the essential mission of the C&O Canal National Historic Park, District and National Park Service planners indicate that these historic facilities will almost certainly be protected. For the most part, however, the National Park Service would not have to armor the existing Potomac River shoreline to protect the canal. Therefore, it is most appropriate to assume that most of the land between the river and the towpath probably will not be protected ; to preserve the integrity of the canal, the draft map assumed that the land within 100 feet of the canal will almost certainly be protected.
The District of Columbia also has two islands in the Potomac River: Columbia and Theodore Roosevelt islands. Columbia Island is across Boundary Channel from the Pentagon, and is often mistakenly assumed to be in Virginia given its proximity to the Virginia shore. The Potomac shore of Columbia Island is occupied by George Washington Parkway and the Mt. Vernon Bicycle Trail; the island also has a marina and a picnic area. Given its heavy use and the fact it is already armored, it will almost certainly be protected for the foreseeable future. Theodore Roosevelt Island, by contrast, has natural shores and is intended as an urban preserve. Therefore, this island will probably not be protected as sea level rises, and thus was depicted in blue.
Much of the Anacostia shore is also armored. Along the east bank from Poplar Point to the Potomac, the land reclaimed from the Anacostia River for the Naval Air Station is only a few feet above sea level, and hence is protected with a dike. On both sides of the river, bulkheads stabilize most of the shore. The federal government is working with the District of Columbia to restore this often-neglected river. Recognizing that the shore is less developed upstream from the CSX railroad bridge, the long-term plan embodied in the City's Anacostia Initiative aspires to achieving maximum ecological integrity upstream of the CSX crossing, with a more modest degree of habitat restoration downstream, as shown in Figure 4. The Anacostia Initiative has integrated the District of Columbia's assessments and plans for the river's shoreline and, as such, provides the basis for the shore protection map of this chapter.
The environment portion of the Anacostia Initiative has two key components that are closely related to the shore protection question. First, the City is specifying buffers of various magnitudes along the waterfront, as shown in Figure 5. Second, the City intends to replace the "seawall" along both sides of the river with more environmentally benign shore protection or, where possible, natural shores. Figure 6 shows the City's plan, which the City has summarized as follows:
---newly constructed bulkhead (Near Navy Yard): 1.1 miles
---other new bulkheads to be constructed: 0.82 miles
---existing bulkhead to be maintained: 2.5 miles
---existing seawall to be converted to bioengineered edge: 3.2 miles
---existing seawall to be removed as needed: 11.0 miles.
Unlike in suburban and rural areas, the conscious decision to maintain natural shores does not necessarily imply that shores will not be protected in an urban area like Washington. Just as the need to keep natural beaches has motivated populated oceanfront communities to use beach nourishment, the District of Columbia is currently inclined to use environmentally sensitive means of shore protection rather than allowing wetlands to migrate inland. Nevertheless, the relatively pristine land cover upstream of the Benning Road power plant, planned buffers, and projects to remove seawalls combine to suggest that shore retreat is possible-albeit unlikely-in these areas. Therefore, our shore protection map for the District of Columbia Anacostia Shoreline shows a number of areas in blue or red.
For further details, please see the discussion of the Districe of Columbia's likely response to sea level rise, which summarizes a conversation between Jim Titus and Uwes Brandes of the DC Office of Planning
Governments Plan for Development of Most Land Vulnerable to Rising Sea (PDF, 7 pp., 1.3 MB) was originally published in Environmental Research Letters , Issue 3, Volume 4 (2009).