Baltimore and Annapolis are likely to suffer serious coastal flooding again before this century is over, and people and property in Ocean City and on the lower Eastern Shore face even greater risks as climate change accelerates sea level rise along Maryland's extensive shoreline, warns a new report.
Drawing on new government data and projections, Climate Central, a nonprofit research and information group, calculates that 41,000 homes with 55,000 residents in the state are in danger under mid-range sea-level rise projections if storm-driven flooding surges five feet above the high tide line -- which it did in the Baltimore area and elsewhere during Tropical Storm Isabel in 2003.
But the number at risk jumps to 94,000 homes with 132,000 residents if worst-case projections of rising seas combine with a major storm to cause flooding up to 9 feet above high tide, the group's report says.
Ben Strauss, lead author of Climate Central's report, said recent climate-change projections and land elevation data make it possible to get specific about the the threats to people, property and infrastructure from flooding worsened by climate change. The group has developed an online "surging seas risk finder" mapping how Maryland communities from Baltimore to Somerset and Worcester counties could be hit by storm flooding, depending on how much sea level rises.
Climate Central's report comes on the heels of a survey released Monday by the O'Malley administration that found 73 percent of Marylanders want state and local governments to protect their communities against the impacts of climate change. More than half also said shielding coastal areas from sea-level rise should be a high or very high priority.
"Marylanders clearly understand that extreme temperatures and more severe storms are likely results of climate change that will occur in their communities in the next decade or two," Governor Martin O'Malley said in a statement announcing the survey by George Mason University. It was underwritten by Town Creek Foundation.
But at the same time, most Marylanders surveyed also said they don't know whether sea level is currently rising along Maryland's shorelines.
"Many people in Maryland aren't sure if sea-level rise is happening, or if it is human-caused, which suggests the need for more education about how climate change will affect our families and communities," said Karen Akerlof, the survey's lead investigator at George Mason University.
Tide gauge readings have documented rising sea level along the Mid-Atlantic coast and in the Chesapeake Bay averaging 3 to 4 millimeters per year. Scientists say sea level has risen about one foot in the bay over the past century – a rate nearly twice the global historic average. Maryland's rate is higher because of land subsidence, which is estimated to be occurring at 1.3 millimeters annually.
Zoe Johnson, head of the Office for a Sustainable Future in the state Department of Natural Resources, said she hopes the detailed Climate Central map will help educate more Marylanders about the impact of rising seas.
Maryland is particularly vulnerable to flooding because of its lengthy ocean and Chesapeake Bay shoreline and extensive low-lying coastal lands. But the impact of rising sea level on potential flood damage varies around the state, the Climate Central analysis found.
More than $19.6 billion in property value -- more than 40 percent of it in Worcester County, and a third in Ocean City -- lies within five feet of the high tide line, putting it at risk of storm-driven flooding under even intermediate sea-level rise projections, the report says. The property in jeopardy increases to $42.3 billion if climate-aggravated flooding rises nine feet above current high tide, the group notes.
Warming-related sea level rise has already increased the likelihood of extreme floods by some 20 percent in and around Baltimore and Annapolis, the report estimates. The increased likelihood is more than 30 percent at Lewes, Delaware and Ocean City, more than 40 percent at Cambridge, and more than 70 percent at Solomons Island.
Somerset and Worcester counties face the biggest flooding impacts, Climate Central concludes, with between 30 and 50 percent of their homes and other assets located within five feet of the high tide line. In Somerset, 47 percent of homes are below five feet, and in Worcester, 30 percent of homes.