Hurricane Katrina’s damage wasn’t all to man-made objects: the storm also hit the marshes and swamps surrounding New Orleans. The city has done a good job of regrowing over the last decade, but the landscape is still showing scars.
NASA has published a three images captured by its Landsat satellites. The first shows the marsh area to the souteast of New Orleans a week before Katrina hit; the second is from two months after Katrina, and the final image is from a few weeks ago. The false-colour images reveal how much damage Katrina caused which has not been healed: green shows healthy vegetation, brown shows flood-damaged areas, and blue is water.
The Earth Observatory explains how Katrina caused so much damage:
Pounding surf, driving winds, and a potent storm surge transformed the marshes by picking apart mats of dead grass, stirring up and disbursing soft underlying sediments, scouring several new channels, and depositing leftover sediment and debris in new areas.
Katrina delivered a massive surge of water that dramatically enlarged lakes, including Lake Lery and Petit Lake. It also scoured new channels and widened canals in ways that eliminated large amounts of marshland. As seen in the 2015 image, flood-damaged vegetation has returned to its normal colour, but the enlarged waterways have persisted.