Ben Duckworth spent the night of August 17, 1969, clinging to an old oak tree in Pass Christian, Mississippi. He held tight to the tree trunk as sustained winds of over 175 miles-per-hour whipped in off the Gulf of Mexico, and a 24-foot wall of water slammed into the coast, washing away everything in its path. Hurricane Camille came ashore about midnight and started ripping apart the Richelieu Manor Apartments, where Ben huddled with several other people. His escape to the roof of the three-story building was cut short when wind and water swept him from the roof, carried him inland, and slammed him into the tree that saved his life. In the morning, there was nothing left of the Richelieu except for the foundation slab.
Thirty-six years after Ben’s night from hell, hurricane Katrina charged northward across the Gulf of Mexico, bringing a 25-foot storm surge. At landfall on August 29, 2005, a mountain of water collided with the Louisiana coast, overwhelming New Orleans’ flood defenses and submerging the city. Katrina became the costliest tropical cyclone on record, leaving over 1800 people dead and a final damage bill of $168 billion (inflation-adjusted).
Storm surge is only one of several types of flooding triggered by hurricanes, but its onslaught is rapid, and the damage it wreaks is sometimes unpredictable. Storm surges are killer events driven by low atmospheric pressure and wind, not rain.
How storm surge works
The two factors controlling storm surge are atmospheric pressure and wind strength. Atmospheric pressure in the center of a hurricane is lower than on the outer edges. This pressure differential causes water to mound up beneath the eye of the storm. The lower the pressure, the higher the water rises. But the pressure surge is not as devastating as the wind-driven surge.
Hurricane winds in the northern hemisphere blow around the eye of the storm in a counterclockwise direction. When Camille and later Katrina made landfall, the winds on the east side of the eye blew landward. Caught between wind shear at the ocean surface and frictional resistance on the shallowing ocean bottom, the seas mounded up, creating a massive wind-driven surge.
The pressure and wind work together to produce the total storm surge. By the time the Richelieu Apartments collapsed during Camille, the storm surge had inundated the two lower floors. The surge is more akin to a tidal wave that a normal wave. The pressure it applies against any structure is a relentless push landward. A push that lasts until the storm passes. Very little can stand in the way of a massive storm surge.
Storm surges and climate change
Storm surges are driven by wind, pressure, and water, and are not a product of climate change. But climate change makes storm surges more dangerous. Climate change brings warmer ocean waters and stronger hurricanes. Recently published research (Kossin et al.) analyzed 40 years of hurricane data showing the frequency of category-3 storms has increased since the 1980s. This observation doesn’t mean every hurricane is stronger, or more category-3 hurricanes occur every year. But it does tell us category-3 storms are more likely in any given year, and storm intensity is increasing on a decade-by-decade basis.
Due to climate change, increasing storm intensity means the risk of severe storm surge flooding is on the rise—bad news for coastal communities on the Atlantic and Gulf coasts.
ArcheanWeb:
Hurricanes more dangerous than in the past (Source: ArcheanWeb) – https://archeanweb.com/2020/06/01/hurricanes-more-dangerous-than-in-the-past/ Also:
Natural storm barriers threatened by rising seas and climate change (Source: archeanWeb) – https://archeanweb.com/2020/06/15/natural-storm-barriers-threatened-by-rising-seas-and-climate-change/ Also:
Cascading natural events: The perfect storm (Source: ArcheanWeb) – https://archeanweb.com/2020/06/02/cascading-natural-events-the-perfect-storm/ Also:
Sources
Hurricane Camille (Source: PassChristian.net) – http://camille.passchristian.net/hurricane_party.htm Also:
Global increase in major tropical cyclone exceedance probability over the past four decades (By James P. Kossin, Kenneth R. Knapp, Timothy L. Olander, and Christopher S. Velden; PNAS) – https://www.pnas.org/content/117/22/11975 Also:
Feature Image: The aftermath of Hurricane Camille (Modified) – By NOAA – http://www.photolib.noaa.gov/historic/nws/wea00597.htm, Public Domain, https://commons.wikimedia.org/w/index.php?curid=1364878