Coastal Change Hazards: Hurricanes and Extreme Storms

Hurricane Isaac

Lidar Elevation: Comparisons of the post-storm elevation data to lidar data collected prior to Isaac's landfall are used to characterize coastal change.

Pre- and Post-Storm Photo Comparisons: Before and after photo pairs show examples of coastal change resulting from Hurricane Isaac.

Post-Storm Photos: Photography for the Central Barrier Islands. View photos.

As Hurricane Isaac churned toward the northern gulf coast in August 2012, U.S. Geological Survey scientists worked to determine where and how the storm's waves and surge might dramatically reshape the beaches and dunes that stand between the storm and coastal developments. Through a complex modeling process that uses coastal elevations, wave forecasts, and potential storm surge, they predicted coastal change hazards, such as shoreline and dune erosion, that might be expected during an Isaac landfall.

Using the latest storm information available, USGS predicited the likelihood of a range of coastal change impacts within the region affected by this storm:

• Louisiana's Chandeleur Islands were very likely to inundate due to storm surge and waves.
• Dune erosion was very likely for the majority of the sandy beaches along the Mississippi and Alabama coasts.
• For islands west of the Mississippi River, models predicted extensive beach and dune erosion as well as intermittent overwash.

Alabama's Dauphin Island, which has suffered repeated impacts from hurricanes over the last decade, was again battered by hurricane waves and surge. In 2005, Hurricane Katrina hit this barrier island just as it was recovering from Hurricane Ivan's landfall one year earlier. Three years later, Hurricanes Gustav and Ike attacked an already eroded shoreline. Beach erosion and overwash from Hurricane Isaac has continued to reshape this tiny island, perhaps increasing its vulnerability to future storms.

Following landfall, oblique aerial photography and lidar surveys of beach elevations were used to document the changes that occurred as a result of the storm. Comparisons with data collected before the storm show the nature, magnitude and spatial variability of the coastal response. These data will be used to further refine predictive models for storm-induced erosion.

Repeated attacks by hurricane waves and surge have taken a toll on Dauphin Island, Alabama, carving a breach in the narrow island, toppling beachfront homes, and eroding large stretches of coast. [larger version]

Response Activities

Pre-landfall

• Updated assessment of potential coastal-change impacts (web post, updated 08/28/12)

Post-landfall (approx. 3-10 days)

• Pre- and post-storm photo comparisons (web post, updated 09/06/12)
• Oblique aerial photos of impacted coast (web post, updated 09/07/12)
• Post-storm airborne lidar topographic survey (web post, updated 10/19/12)

National Hurricane Center
National Weather Service