HOME          SITE MAP          NEWS          CONTACT



Erosion
Storm Effects on Dauphin Island

Tropical hurricanes and winter storms have devastated the island over time.  Historic data indicate that 2005 was the most active year of record for the Atlantic Basin. A total of 28 named storms occurred in that year, with five making landfall along the northern Gulf Coast.

Of these Katrina and Rita were the most noteworthy since they were classified as Category 5 storms during a part of their life and were extremely powerful events when they struck the coast, affecting extensive coastline areas well to the east of the actual landfall point.

Hurricane Katrina resulted in the loss of an average of 2.3 feet in elevation on the south beach at Dauphin Island’s west end, with the island shifting between 87 to 492 feet to the north during this single catastrophic event.

Tide Lines with Lot Line Overlays
Pre-Isadore (2002) & Post-Katrina (2006)
(click photo to enlarge)

Other storms which have exacted severe damage to the island:

  • Hurricane Frederick (Category 3) caused major damage to the island in September 1979, being the “signature” storm event for many years.

  • Hurricane Elena (weak Category 3) came close enough to the island to have a significant impact in August 1985.

  • The decade between 2000 and 2010 saw a large number of tropical systems impact Dauphin Island. Hurricane Ivan (Category 3) and Hurricane Katrina (Category 3) in September 2004 and August 2005, respectively, are the most recent hurricanes to have severely altered the shoreline configuration of and elevations on Dauphin Island.

  • Tropical Storm Isidore in September 2002 destroyed the FEMA berm along the island’s western south shore.

  • Although Hurricane Ike (strong Category 2) made landfall in Galveston, Texas, in September 2008, the immense size of that storm generated considerable wave action at Dauphin Island that aggravated coastal erosion problems.

Each year since Hurricane Katrina, small but more frequently occurring storm events are having increasingly adverse effects on the morphology of Dauphin Island. The heightened tropical storm activity between 2000 and 2010 has lowered the elevation of the West End of Dauphin Island and greatly eroded the shoreline.

As a result, small storm events that would previously not have had much effect on Dauphin Island are now causing significant overwash events that carry increasing quantities of sand to the northern shoreline. The frequency of these events hinders the establishment of vegetation necessary to hold the sand, which allows further losses due to wind between storm events.

Overwash
(click photo to enlarge)

The effects of the smaller storms began to be especially apparent during the winter and spring of 2008-2009 and are continuing to impact Dauphin Island beginning in November 2009. The only tropical system to affect Dauphin Island made landfall on November 9. Ida barely met the wind strength as a weak Category 1 hurricane and was downgraded to a tropical storm before it made landfall. But while Ida only produced maximum sustained winds of 45 mph, the extremely weakened state of the western end of Dauphin Island made it susceptible to considerable shoreline erosion. Examination of the hourly wind speeds and maximum gusts created by this 3-day (November 8-10) storm event on Dauphin Island show that sustained winds during Ida generally ranged between 20 and 30 mph during this period.

There is no question that naturally-occurring storms effect damage to Dauphin Island and contribute to erosion. Yet even with heavy storm activity, the island was able to reestablish itself in the past.  This reestablishment pattern has been all but lost since the interruption in the natural littoral drift system caused by maintenance dredging in the Mobile Outer Bar Channel.


Related Links

More factors contributing to erosion

 

 

Copyright © Dauphin Island Restoration