How do barrier islands protect the mainland

Because the Mississippi River has been dredged and enclosed between levees to keep it from spilling over its banks, this area does not receive the sediment loads that the river once deposited in this part of the Gulf. As a result, the islands are eroding and disappearing. To slow this process, state and federal agencies are artificially nourishing the islands to keep them in place and preserve the cities, livelihoods and ecological habitats behind them.

Geologically, barrier islands are not designed to stay in one place. But development on them is intended to last, although critics argue that climate change and sea level rise will inevitably force a retreat from the shore.

People will always be drawn to the coast, and prohibiting development is politically impractical. However, there are some ways to help conserve barrier islands while maintaining areas for tourism activities. First, federal, state and local laws can reduce incentives to build on barrier islands by putting the burden of rebuilding after storms on owners, not on the government.

Many critics argue that the National Flood Insurance Program has encouraged homeowners to rebuild on barrier islands and other coastal locations, even after suffering repeated losses in many storms. Second, construction on barrier islands should leave dunes and vegetation undisturbed. This helps to keep their sand transportation systems intact. When roads and homes directly adjacent to beaches are damaged by storms, owners should be required to move back from the shoreline in order to provide a natural buffer between any new construction and the coastline.

Third, designating more conservation areas on barrier islands will maintain some of the natural sediment transportation and barrier island migration processes. And these conservation areas are popular nature-based tourism attractions. Finally, development on barrier islands should be done with change in mind and a preference for temporary or movable infrastructure. The islands themselves are surprisingly adaptable, but whatever is built in these dynamic settings is likely sooner or later to be washed away.

Portsmouth Climate Festival — Portsmouth, Portsmouth. It is remarkable that although they constantly change and may become badly eroded some even disappear entirely , they can rebuild if left alone. There are several theories as to how barrier islands form.

During glacial advances, huge amounts of water were locked in glaciers causing the sea level to fall. Then, during interglacial periods when it was warmer, the ice melted, causing sea level to rise. Georgia was never covered by glaciers but it was affected by the rising and falling of the sea level about 40 million years ago. During the Pleistocene, in warm periods, sea level may have been as much as 50 to feet higher than today with the ancient coastline lying along a sand ridge known as Trail Ridge.

During times of extreme cold, the shoreline lay as much as 80 miles seaward of its current position. The older islands formed thousands of years ago when sea level rose flooding the coastline. Dates for their formation are unclear and could have been any where from 25, to , years ago. Ridges of sand dunes were left above sea level and gradually built into barrier islands. Over the next few thousand years sediments from rivers added material to fill in the area between these new islands and the mainland producing mud in which the vast expanses of salt marsh formed.

As sea level stabilized these small remnants of old sand dunes gradually built into our older barrier islands. About 11, years ago near the end of the Pleistocene, sea level rose again, flooding the coastline to its present location. About 5, years ago the rise in sea level slowed to about four to six inches per century, allowing the formation and growth of our newer Holocene islands.

Today sea level is rising a little more than one foot per century. Each period of ice formation and melting created a new sequence of barrier islands along the coast of Georgia. The oldest series of islands, the Wicomico Shoreline, formed when sea level was as much as 95 to feet higher than it is today and is responsible in part for the creation of the Okefenokee Swamp. The next series of barrier islands, called the Penholoway Shoreline formed when sea level was 70 to 75 feet above its present level.

The Talbot shoreline formed when sea level was 40 to 45 feet higher; the Pamlico shoreline formed when sea level was 25 feet higher. The Princess Anne shoreline formed when sea level was 15 feet higher, the Silver Bluff shoreline formed when sea level was 5 feet higher. The Georgia Department of Natural Resources DNR will host an online public meeting to receive input on a proposed mariculture zone for oyster farming in Chatham County at 5 pm.

Tuesday, Nov. Spotlighting the latest Buzzworthy news from Coastal Resources Division. Geological Survey A significant effect of storms is the excavation of new inlets.

This type of barrier breaching is more likely to originate from the bay side than from the ocean side, which may come as a surprise. According to Pinet , the excavation results from a combination of factors.

First, the bay becomes swollen with water due to abnormal storm precipitation, increased runoff from both the mainland and the barrier island, and inflow driven by the storm surge offshore. Second, the strong onshore winds that lash the area create a storm surge not only against the seaward side of the barrier but against the mainland, so that the water surface of the bay slopes downward toward the barrier island.

As the storm and its onshore winds dissipate, water in the bay sloshes back against the barrier, occasionally overtopping the island at its most vulnerable, low-lying points and cutting a channel through it.

The new inlet serves as a discharge conduit for the large volume of excess water trapped in the bay. Additionally, the process of inlet construction may be enhanced by winds that veer from an onshore to an offshore direction as the storm center passes the site, blowing bay water though the newly formed inlet.

In many cases, the storm-generated inlet is short-lived because the nearshore drift of sand quickly closes the passage on its ocean side. However, along narrow barriers that have few tidal inlets e. Stormflow from major rivers on the mainland can also scour an inlet, helping to maintain the opening Webb et al.

Inlets along microtidal coasts, such as the Gulf Islands, tend to close unless substantial outflow from a major river interferes. Storm surge enables large waves to reach far into the interiors of barrier islands, at times breaching the islands. At Gulf Islands National Seashore, overwash during surges of major hurricanes e.