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August 2012

Atlantic Hurricane Tracking Chart

Atlantic Hurricane Tracking Chart

The Gulf of Mexico covers more than 700,000 square miles in Southeast North America. It runs along the southern coast of the United States from Florida to Texas, and the eastern coast of Mexico from Tamaulipas to Yucatán. Near the entrance of the Gulf is the island of Cuba. It is connected to the Atlantic Ocean by the Straits of Florida; it connects to the Caribbean Sea by the Yucatán Channel. The Atlantic hurricane season officially ranges from June 1 through November 30.

Hurricane Isaac (category 1) hit Louisiana on August 29th, 2012, seven years after Hurricane Katrina (category 5) hit the in the same region. U.S. Geological Survey scientists are working to reduce this uncertainty. Through a complex modeling process that uses coastal elevations, wave forecasts, and potential storm surge, they can predict where and how a storm threatens to dramatically reshape the beaches and sand dunes that stand between the storm and coastal developments.

Elevated water levels and waves during tropical storms can lead to dramatic coastal change through erosion of beaches and dunes. USGS has developed a storm-impact scale that predicts the likelihood of coastal change by comparing modeled elevations of storm-induced water levels to known elevations of coastal topography in order to define three coastal change regimes. The three regimes are collision, overwash, and inundation. Collision occurs when waves attack the base of dunes and cause dune-front erosion. Under higher surge or wave runup conditions, waves can overtop dunes leading to overwash, which can include dune erosion, landward dune migration, and overwash deposition on low, narrow islands. In extreme cases, such deposition can bury roads and parts of buildings. The most extreme coastal change regime is associated with inundation, where the elevation of storm surge plus wave setup exceeds the elevation of the primary dune or beach berm. Under these conditions the beach and dune can be severely eroded and low, narrow islands may breach.

The deepest part of the Gulf, lies off the Mexican coast. The shoreline is generally low, sandy, and marshy, with many lagoons. Chief of the many rivers entering the Gulf are the Mississippi, Alabama, Brazos, and Rio Grande. The U.S. Intracoastal Waterway follows the Gulf’s coastline from southern Florida to the Rio Grande. Oil deposits from the continental shelf are tapped by offshore wells, especially along the coast of Texas and Louisiana. Most of the U.S. shrimp catch comes from the Gulf Coast.

The Columbia Gazeteer; USGS Coastal and Marine Science Center, 20120828; 20120828

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