Mississippi–Alabama barrier islands

The Mississippi–Alabama barrier islands are a chain of

Recurring major tropical cyclones have periodically altered the islands' shapes through wind, waves, and accompanying storm surges.^[2]: 10 Although severe storms often noticeably disrupt the morphologies and ecosystems of the islands on the timescale of days, vegetation and land area normally recover over a period of years following a major weather event.^[5] The gradual sea level rise in the Gulf during the past century has contributed to the decrease in land area of the island chain, but the effect is not thought to have been large compared with the influence of the removal of sediment from the system through the dredging of shipping channels.^{[2]: 22–24}

Ecology

The interiors of the islands are vegetated, with

Cat Island runs for 3.5 miles (6 km) along the western end of the Mississippi Sound, south of Gulfport. This island has maintained a relatively stable morphology since surveys began, partly due to its relatively high interior elevation. It has a T-shape, with northward and southward spits extending out from its eastern end. Since surveys began, the southward spit has experienced more erosion than the northward one, and all parts of the island have narrowed.^[2]: 8–9

Ship Island

Ship Island runs for 7 miles (11 km) along the western part of the Mississippi Sound, south of Biloxi. This island has experienced major morphological changes over the past two centuries, with its eastern spit rapidly receding, and its narrow central segment shifting toward the mainland. The island's central portion has been repeatedly breached by major storms, most recently by Hurricane Camille in 1969;^[2]: 8 the so-called "Camille Cut" between the western and eastern portions of the island was filled by the United States Army Corps of Engineers in 2019.^[8]

Dog Key Island/Isle of Caprice

The shoals between Ship Island and Horn Island have intermittently formed small islands known as the Dog Keys (the namesake of Dog Keys Pass), which have been mapped at various dates between 1848 and 1940.^[3]: 8 Several smaller shoals grew together into one larger island around the beginning of the 20th century, appearing on a 1917 map from the United States Coast and Geodetic Survey,^[2]: 7 around 3 miles (5 km) long. In 1925 a group of property developers in Biloxi purchased this "Dog Key Island" from the federal government, built a resort and casino on the island, and renamed it the "Isle of Caprice".^[9] By 1932, the island had entirely vanished beneath the surface.^[2]: 7–8

Horn Island

Horn Island runs for 13 miles (21 km) along the central part of the Mississippi Sound. Since surveys began, the island's east end has receded through erosion, while its west end has grown through spit formation at the down-current end. The east end has lost more land than the west has gained, and the island has generally narrowed over the same period.^[2]: 7

Petit Bois Island

Petit Bois Island runs for 6 miles (10 km) along the eastern part of the Mississippi Sound, south of Pascagoula. This island has undergone the most dramatic morphological changes in the island chain during the past two centuries. The wider triangular segment that now forms the island's eastern end was its extreme western end as recently as the 1840s, but, as with neighboring Horn Island, the eastern spit has receded rapidly, while a new western tail has grown more slowly.^[2]: 6–7

Dauphin Island

Dauphin Island, which has over 1200 residents, runs for 15 miles (24 km) at the east end of the Mississippi Sound and marks the western edge of the mouth of Mobile Bay. The eastern quarter of the island is wider and more elevated, while the western end is narrow and more prone to disturbance by storms. The east end includes the town of Dauphin Island. Since surveys began, the long western tail has generally lengthened, due to sand deposition from the longshore drift, and shifted toward the mainland, due to erosion on the Gulf shore and overwash during major storms.^[2]: 5–6

Island maps

• 
  Cat Island
• 
  Ship Island
• 
  Horn Island
• 
  Petit Bois Island
• 
  Dauphin Island

References