Davie, Fla., August 27, 2005 — Winds from Hurricane Katrina knocked over this tree crushing this Mobile home. The residents had evacuated. Many Mobile homes were damaged and residents are displaced. MARVIN NAUMAN/FEMA photo
M. Kieper took this photograph of the Spinnaker Point condos in Pascagoula MS that were destroyed by surge. The partially-remaining damaged condo that remains was one of 40, with the remainder washed away, as seen on page 8 in the MS Press, in a photo taken the day after the hurricane made landfall: http://www.gulflive.com/mississippipress/pdf/083105.pdf
Notice the two deck railing planters, with the plants still in them, remain on the deck of the 2nd floor (three stories above ground level).
Surge (storm tide, technically) here in eastern Pascagoula reached 16-18 feet, and there would have been waves on top of the surge at a location on the waterfront such as this one. The sheetrock has been pulled away from the studs about four feet up on the 1st floor; this likely tallies with the height of the surge.
Source: M. Kieper

Gulfport, Miss., September 6, 2005 — Destroyed houses in Gulfport, Miss. Hurricane Katrina caused extensive damage all along the Mississippi gulf coast. New Orleans is being evacuated as a result of flooding from hurricane Katrina and is still 60% under water. FEMA/Mark Wolfe

Hurricane Katrina damage in Bayou La Batre, Alabama, showing the cargo ship M/V Caribbean Clipper and 4 fishing boats pushed ashore near the bayou.Excerpt from larger NOAA photo: http://www.noaanews.noaa.gov/stories2005/images/katrina-bayou-la-batre-ala-2005.jpg
Two images of the Chandeleur Islands off the coast of Louisiana, USA. The left image is from 2004 and the right is from 2005, after Hurricane Katrina. October 15, 2004 and September 16, 2005. NASA Earth Observatory, Landsat Project Science Office.
Floodwaters from Hurricane Katrina reached the steps of the John A. Campbell U.S. Courthouse in Mobile, Alabama.
In the Southern District of Alabama, flood waters from Mobile Bay reached all the way to the front steps of the John A. Campbell U.S. Courthouse in Mobile, and GSA reported about two feet of seawater in the basement. Power was restored to both the district and bankruptcy courts within a few days. While the court was back in operation, DCN access from Sprint was down for a full three weeks, and it took a month to restore long distance service.
August 29, 2005

New Orleans, Louisiana in the aftermath of Hurricane Katrina (2005:08:29 17:24:22), showing Interstate 10 at West End Boulevard, looking towards Lake Pontchartrain
The 17th Street Canal is just beyond the left edge of the image. The breach in the levee of that canal was responsible for much of the flooding of the city in the hours after the hurricane.
This photo provided by the U.S. Coast Guard shows flooded roadways as the Coast Guard conducted initial Hurricane Katrina damage assessment overflights of New Orleans, Monday Aug. 29, 2005.

Structural bridge damage caused by Hurricane Katrina can be seen from aboard Air Force One Wednesday, Aug. 31, 2005.
Source: White House photo by Paul Morse
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New Orleans, Louisiana.
Gulfport and Long Beach, Mississippi.
Mobile, Alabama.
Cities that were devastated by Hurricane Katrina.
Cities that will not go quietly into the night.
Cities that still live.
Lest we forget.