Geomorphic Recovery of the Chandeleur Islands, Louisiana, after a Major Hurricane

Jacob H. Kahn

Abstract


 

Geomorphic changes in the Chandeleur Islands, Louisiana, were monitored during the two years following the passage of Hurricane Frederic in September 1979. Rates of beach accretion and closure of hurricane channels on these transgressive, microtidal barrier islands were affected by subsequent storms, including major  frontal passages in the winters of 1978-79 and 1979-80 and three tropical cyclones that passed through the Gulf of Mexico in 1980. The hurricane's modification of barrier geomorphology was still evident twenty-four months after Frederic. Fourteen hurricane channels remained open and the mean beachwidth of the islands was 60 m in September 1981. Prior to the hurricane the beach was continuous throughout the study area and the mean beach width was 170 m. The slow, incomplete recovery of the barriers lends support to the hypothesis that the Chandeleurs are evolving from a continuous chain of barrier islands into a series of small islets and shoals. This transformation is a consequence of the frequent passage of tropical cyclones through the northern Gulf of Mexico, the lack of a sediment supply to the Chandeleur barrier system, and the subsidence of the relic St. Bernard Delta surface underlying the islands.


Keywords


Barrier island; beach accretion; Chandeleur Islands; geomorphic change; Hurricane Frederic; overwash; tropical cyclone

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