Ivan causes an 'extreme coast change'

Experts are comparing this weekend's photos with ones from 2001.
SCRIPPS HOWARD NEWS SERVICE
An initial round of aerial photo comparisons shows there's a lot less barrier between the Gulf of Mexico and the mainland coast of Alabama and Florida after Hurricane Ivan's passage.
A storm surge capped with breaking waves rose two stories or better along the northeast path of the hurricane as it made landfall with winds near 130 mph near Gulf Shores, Ala., early Thursday.
"The Gulf spilled across the barrier islands in a strong current capable of transporting massive amounts of sand landward, undermining buildings and roads, and opening new island breaches," said Abby Sallenger Jr., a Florida-based oceanographer with the U.S. Geological Survey.
"We've certainly seen examples of extreme coast change in the comparisons we've done so far."
Making a comparison
The researchers have been using photos from a survey of the coastline done in July 2001 and comparing buildings and natural features in them with new images taken over the weekend.
Sallenger has been working over the past several years on a project to map changes in the U.S. coastline that affect its vulnerability to hurricanes and other strong storms. He is also studying the long-term effects of sea-level changes.
The new photos clearly show that eroding sand from the beaches of places such as Alabama's Romar Beach, Orange Beach and Pine Beach contributed to the undermining and collapse of some structures. Complete understanding of the causes of the damage -- how much from erosion, how much from waves and how much from high winds -- will have to await analysis by engineers.
"There were a lot of areas that had only 6 feet of elevation above sea level to begin with," said Sallenger, who refers to those dunes as the "first line of defense" for any coastal community facing a storm.
Getting detailed data
More precise information about new elevations of dunes and beaches will come from radar scans done from a NASA aircraft flying along the coast Sunday in a pattern that had to dodge airspace closed because of President Bush's visit to the region. That information won't be analyzed for several more weeks.
In the meantime, Sallenger and colleagues are looking at clues from the ground and air to calculate the lost sand -- how high the now-exposed pilings from a lost cottage extend into the air, when they were once mostly beneath a dune or how far inland an over-washed section of beach dropped sand.
At least one stretch of Pine Beach near Gulf Shores was scoured out completely by the storm surge, leaving a shallow new inlet to Little Lagoon several hundred feet wide.
It will take months for Sallenger's team to update the detailed maps they've done to estimate storm-surge-damage potential for this section of coastline, as they've done for all the more hurricane-prone waterfronts of the nation.