When it comes to the marshes, beaches and barrier islands along the Gulf Coast, big storms like Hurricane Katrina give -- and they take away. That's the lesson becoming clear from satellite images and aerial photography that federal government researchers are now releasing.
The before-and-after images show that, in many places, high winds, heavy waves and powerful storm surges picked up tons of sand and silt and pushed it far inland, filling navigation canals and burying roadways and railroad tracks. In others scenes, the storm has gouged holes in wetlands and washed away sand beaches, creating huge submerged sandbars offshore and leaving remaining patches of green vulnerable to further erosion.
Coastal researchers says it's common for big storms to create such dramatic changes. And they predict that, over time, some beaches will naturally rebuild themselves. But they are eyeing the damage that Katrina has done to the region's coastal wetlands with concern. That's because the marshes provide an important buffer against big storms. Some scientists estimate that a three-mile-wide band of healthy wetlands can reduce storm surges by about foot - often just enough to prevent floodwaters from surging over levees.
That wetland buffer has been shrinking over the last century. In Louisiana, for instance, officials estimate the state has lost nearly 2,000 square miles of wetlands over the last 70 years. And despite restoration efforts, researchers say losses continue at a rate of about 25 square miles a year. Within a few months, researchers studying the before-and-after images from Hurricane Katrina should be able to show just how much wetland damage the storm did.
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