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al., 2010). Recent evidence also confirms the instability of glaciers
in West Antarctica, which has the potential to raise global sea
levels significantly, particularly beyond AD 2100 (Joughin et al.,
2014; Rignot et al., 2014). As global sea levels rise and the
Chesapeake Bay region subsides, storm surges are projected to
increase both in frequency (IPCC, 2013) and magnitude (Tebaldi
et al., 2012). Superimposing Hurricane Isabel water levels on the
range of RSLs we predict for the Cheapeake Bay region would
cause a storm tide of ~3.8–4.6 m in Washington D.C. and ~2.8–
3.5 m for Chesapeake Bay (NOAA, 2003). Given the location of
the Chesapeake Bay region along the path of storms tracking up
the Atlantic coast (Fig. 1), increasing RSL rise will further exacer-
bate already high costs of storm damage, such as the US$65
billion price-tag associated with Hurricane Sandy (NOAA, 2013).
Even the most conservative estimate of projected RSL rise poses
significant threats to the Chesapeake Bay region. Bridges, military
facilities, national monuments, and portions of the rapid transit
system would be flooded in Washington D.C., and ~70,000 resi-
dents would be impacted by a 0.4 m rise in sea level (Ayyub et al.,
2012). Island communities in Chesapeake Bay are particularly
vulnerable to RSL rise. The last two inhabited islands in
Chesapeake Bay are ~1 m above sea level; they occupy the same
geomorphic surface as the western portion of our field area and
will experience similar rates of subsidence. In the Blackwater
National Wildlife Refuge, a LiDAR-based inundation study using
a conservative model for sea-level rise shows that the majority of
tidal marsh will be inundated by AD 2050 (Larsen et al., 2004).
The elevated risk of flooding in the Chesapeake Bay region is
already triggering a societal response. At the Blackwater National
Wildlife Refuge, managers are designing corridors for the land-
ward migration of habitat through easements and land acquisition
to ensure the persistence of tidal marsh beyond AD 2100. Similar
options are increasingly limited on other coastlines, where
continued development and site modification for housing severely
limit the potential for inland migration of habitat, and wetland
loss significantly reduces natural buffers to storms in these regions
(Titus et al., 2009). Island communities have limited options;
some Chesapeake Bay islands have been abandoned due to sea-
level rise in the past century (e.g., Gibbons and Nicholls, 2006).
For Washington D.C. and other coastal cities, risk assessment
and adaptation planning based on the full range of possible RSL
rise scenarios is critical. The analysis by Ayyub et al. (2012) indi-
cates significant losses for Washington D.C. with a rise of 0.4 m,
well below the minimum predicted rise of sea level for AD 2100 of
0.49–0.98 m. This analysis under-predicts the most likely RSL rise
over the next century, in part because it does not explicitly
consider that GIA will drive increased RSL independent of climate
change. We conclude that risk assessments and adaptation plan-
ning for sea-level rise should consider the full range of sea-level
estimates (e.g., Miller et al., 2013) and take local subsidence values
into consideration, particularly for high-density population
centers like Washington D.C.
ACKNOWLEDGMENTS
This research is supported by the U.S. Geological Survey. M. Whitbeck
(USFWS) granted access to the Blackwater National Wildlife Refuge. USGS
drillers E. Cobbs and J. Grey made this work possible. We thank M. Nelson,
A. Benthem, I. Clark, H. Pierce, J. McGeehin, D. Powars, S. Zimmerman,
J. Smoot, and D. Granger for help with this research. M. Pavich and one
anonymous reviewer reviewed this manuscript.
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