What Is A Barrier Island?

Barrier islands are natural island formations that occur parallel to the coast. Barrier islands are constantly changing and can provide a natural habitat for marine life and birdlife.

How are Barrier Islands Formed?

Barrier islands form as a result of sediment being deposited parallel to the coast. The exact formation is debated somewhat and there are several theories regarding barrier island formation:

Barrier Island Formation Theory 1: Offshore Bar

First published in 1845, this theory suggests that barrier islands form as a result of waves churning sand in shallow water and then depositing it when losing their energy and breaking.

Barrier Island Formation Theory 2: Spit Accretion Theory

In 1885, Grove Karl Gilbert argued that barrier island development occurs as a result of longshore sediment. He believed that the sediment moved in from the breaker zone after agitation from longshore drift.

Barrier Island Formation Theory 3: Submergence Theory

William John McGee believed coastal ridges were being separated from the mainland as a result of submergence and that lagoons formed behind these ridges.

Where Are Barrier Islands Located?

Barrier islands are usually:

  • Long
  • Narrow
  • Located close to the mainland

There are barrier island chains all over the world, including many examples right here in the United States.

Some of the most famous barrier islands include:

Hatteras Island, North Carolina

Hatteras Island is popular with tourists and spans 50 miles in length, making it one of the longest in the US. It is home to seaside communities and wildlife and is also unique in that it has a curved section.

Padre Island, Texas

Padre Island is home to one of the many barrier islands in the United States. It is also the longest barrier island in the world, spanning 113 miles in length.

There are longer barrier island chains, though. In 2011, for instance, a much longer chain was discovered near the coast of Brazil.

Great Barrier Island, Hauraki Gulf, New Zealand

Great Barrier Island has an area of 110 square miles, making it the sixth-largest island in New Zealand.

There is a lot of wildlife living on the island and it’s also home to around 1,000 people. It has been described as being a time capsule of sorts, with the locals seemingly living several decades in the past.

Louisiana Barrier Islands

It has been estimated that Louisiana’s barrier islands will soon disappear as they are eroding at a rapid rate. There were created as a by-product of the Mississippi River Delta and Grand Isle is the only one that’s home to a permanent settlement.

Why are Barrier Islands Important?

Barrier islands help to protect coastal communities from extreme weather. They absorb energy from the waves and reduce the devastating impact of hurricanes.

Barrier islands are thought to protect around 10% of the world’s coastlines, reducing wave energy that would otherwise cause billions of dollars in infrastructure damage.

However, rising sea levels are causing problems for many barrier islands around the world. In North Carolina’s Outer Banks, for instance, sea levels rose by up to 5 inches from 2011 to 2015, and these problems are dooming the state’s famous barrier island.

When the sea levels rise and the barrier islands disappear, the coastline could be hit with regular flooding. There are also thousands of residents on the Outer Banks and a billion-dollar tourism industry, all of which could be eradicated.

Summary: What is a Barrier Island?

Barrier islands form naturally and help to protect coastlines all over the world. But with rapid sea-level rise, they are being threatened and the communities built upon them are seemingly doomed.

The Outer Banks is a great example of this, and it could be completely eradicated in just a couple of decades.