Storm Surge & Inundation

Storm surge is an abnormal rise of water generated by a storm, over and above the predicted astronomical tides. Storm surge is produced by water being pushed toward the shore by the force of the winds moving around the storm. The impact on surge of the low pressure associated with intense storms is minimal in comparison to the water being forced toward the shore by the wind. Storm surges are extremely dangerous because they are capable of flooding large coastal areas, causing severe devastation. Along the coast, storm surge is often the greatest threat to life and property from a hurricane. In the past, large death tolls have resulted from the rise of the ocean associated with many of the major hurricanes that have made landfall.

A storm surge driven by winds from a weakening Hurricane Isabel produced the worst Chesapeake Bay flooding in 70 years. Waters up to 8 feet above normal tides surged into lower Fells Point and across Pratt and Light streets into downtown Baltimore. Hundreds of basements and businesses flooded. Hundreds of homes in Bowleys Quarters and elsewhere on the bay shore were badly damaged or destroyed. Property damage reached $410 million in Maryland alone.

Notable Storm Surge Events in the United States:
2012 Hurricane Sandy NY, NJ               13 foot storm surge
2008 Hurricane Ike Galveston, TX         15-20 foot storm surge
2005 Hurricane Katrina New Orleans  25-28 foot storm surge
2005 Hurricane Dennis Florida                7-9 foot storm surge
2003 Hurricane Isabel Maryland                8 foot storm surge
1989 Hurricane Hugo S. Carolina          19.8 foot storm surge

In Baltimore, Fells Point Historic District is in serious danger from flooding because of rising sea levels. Only 3 percent of Baltimore sits in a coastal floodplain, according to the EPA. But because the historic district and the Inner Harbor are in that area, increased flooding is likely to be quite costly for the city. Baltimore already has flooding problems, and they’re likely to be made worse by the rising sea levels coupled with storm surge.

• New research indicates that rising sea level from climate change will roughly double the risks of storm-related flooding in coastal communities in Maryland and nationwide.
• Even small amounts of sea level rise make rare floods more common by adding to tides and storm surge
• Historic local sea level rise rate is1.2 inches/decade. Conservative sea level rise projections by 2050 is 13 inches or more.

Coastal Inundation is the flooding of normally dry, low-lying coastal land, primarily caused by severe weather events along the coasts, estuaries, and adjoining rivers. These storms, which include hurricanes and nor’easters, bring strong winds and heavy rains. The winds drive large waves and storm surge on shore, and heavy rains raise rivers.

As destructive as Isabel was, recent computer simulations by government scientists – the most extensive ever for the Chesapeake Bay – show that hurricane storm surges here could get much, much worse. All low-lying coastal regions, which can cover tens of miles inland, are vulnerable to flooding from storms, and the impact can be substantial. Much of the densely populated Atlantic coastline lies less than 10 feet above mean sea level, within the reach of strong storm surge events.

Inundation events are among the more frequent, costly, and deadly coastal hazards that can impact coastal communities in the U.S. In confined harbors, the combination of storm tides, waves, and currents can severely damage boats, buildings and infrastructure. Salt water intrusion endangers the public health, kills vegetation, and can significantly impact underground infrastructure.

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