Big green and blue dumpsters and a white ice-vending machine sailed like tubby boats down Water and Royal streets, past the submerged mail trucks at the city's downtown Post Office. Water submerged the first floor entrance of Mobile's Exploreum at the foot of Government, and the waves of Mobile Bay whipped the base of the RSA Battle House Tower, the city's half-completed signature skyscraper.
On Dog River, the Mobile Fire-Rescue Department's Swift Waters rescue team pulled at least 30 people to safety as sea water inundated homes along the banks of that river. Emergency workers fear they'll find hundreds of homes on Dauphin Island to be a total loss when the Gulf finally retreats to its familiar shoreline.
Katrina's storm surge, estimated to be somewhere between 11 and 12 feet at the Mobile state docks, was much higher than any recorded in Mobile's modern memory -- much higher than Hurricane Frederic's in 1979, and several feet higher than Hurricane Georges' wake, which pumped more than 8 feet of water into Mobile in 1998.
Katrina's reach may have been at least a few inches higher than downtown's previous high water mark -- a flood of water standing 11.6 feet above sea level, pushed into the city by an unnamed hurricane in 1916.
Storm surges -- a virtual wall of water bulldozed onto shore by the winds of tropical storms -- are often considered to be the most devastating aspect of a hurricane. Through much of the 20th century, storm surge accounted for the overwhelming loss of life associated with such storms.
Though reports have been slow to come in -- tidal guages were in many cases knocked out by the storm -- the height of Katrina's storm surge along the Mississippi Coast is apparently the worst since Camille, whose wall of water was responsible for more than 100 deaths. But Katrina's surge battered a coastline that is far more densely developed and populated than it was in 1969 when Camille struck, and the damage to property may be much greater.
Areas such as Mobile Bay and the Mississippi Coast are considered to be exceptionally vulnerable, primarily because their ragged, shallow-water coastlines are perfectly designed to maximize the effects of hurricane surges. Surges are produced when the deep-water turbulence stirred up by hurricane winds moves up onto the continental shelf. The turbulence, in essence, has nowhere to go but up, and the overall level of the ocean rises several feet above normal.
But the surge often continues to increase in height as it moves inland, encountering still shallower water, and the shores of islands and bays, which virtually squeeze the water to new heights. Surges are also much more severe on the east side of northern Gulf storms. On the east side of these circular storms, winds blow steadily from the south, driving waters into shore; on the west side, prevailing north winds can actually drain water away from shore.
As a result, storm surge heights greater than 20 feet are believed to have developed in the back bays and inlets around Bay St. Louis, Biloxi and Gulfport in Mississippi, just to the east of Katrina's landfall.
Katrina's surge effect was felt strongly as far east as Mobile Bay and Pensacola, even though the center of the storm struck more than a hundred miles away.
In some areas surrounding the Bay, the surge appeared to be even higher. Mike Eubanks, who was working with the Mobile rescue workers on Dog River, said that "every canal and tributary" connected to the River is flooded. He said his crew spent most of the day Monday rescuing some 30 stranded residents from waterside suburbs such as Cypress Shores.
Residents along Robinson Bayou estimated that Katrina's surge was at least 5 to 6 feet higher than the 8- to 9-foot surge produced by Georges, which was this generation's previous high water mark.
"Never in my life -- 33 years here -- have I seen water like this," said Voncille Sadka, who said she left her Austin Street home about 2:30 p.m. Monday when the water in her house rose to her waist.
Most of the other homes in the neighborhood also appeared to be flooded. Sadka added that she, like many of her neighbors, didn't have flood insurance.
Though Gulf Shores and Orange Beach appeared to have escaped with storm surge heights significantly below those recorded last year during Hurricane Ivan, Katrina's waters appeared to have risen to surprising heights in the more inland areas of Baldwin County. The swollen waters of Weeks Bay began pouring over U.S. 98 at Yaupon, near the Fish River Bridge. An emergency official working in the area said he never recalled that happening before.
(Register reporter Marc Anderson contributed to this story.)