Tropical storm surge from Hurricane Katarina

Hurricane Katarina triggered the late August 2005 flooding of the city of New Orleans,

one of the most catastrophic natural disasters in the history of the USA.

Katarina became a hurricane two hours before hitting the coast of Florida on 25 August, weakened overland, and then became stronger as it moved into and over the Gulf of Mexico. It gained energy over the warmer waters of the Gulf and reached its peak as a Category 5 storm around 1.00 pm CTD on 28 August. At that time the maximum sustained winds were 280 km/hr (175 mph) and the central pressure was 902 mb. By August 29 hurricane force winds extended some 165 km (100 miles) from the centre.

New Orleans after Katarina United States Coast Guard

Landfall on the Louisiana coast was at 0610 am CDT on 29 August. There were record storm surges along the Mississippi Gulf Coast, peaking at 10.4 m (34 ft) at Bay St Louis, Mississippi; even as far away as Mobile, Alabama, there was a surge of 4 m (13 ft).

SLOSH (Sea, Lake and Overland Surges from Hurricanes) Model Category 4 Output (from NOAA) See Box on page 153 of the book

Forecasts for surge levels in field of strongest winds, the right-front quadrant of the hurricane, were forecast at 8.5 m (28 ft). The surge height was increased because of the intensity and extreme size of the storm, the local bathymetry, and the fact that it continued as Category 5 (maximum) Hurricane until just before landfall; the wind intensity also generated extreme waves. New Orleans officials ordered an evacuation as 80% of the population were living below sea level along Lake Pontchartrain. On 29 August the storm surge caused a breaches of the levees around New Orleans, and most of the city was flooded, in some places to more than 6 m (20 ft).

Disaster declarations covered a huge area, 233,000 square km (90,000square miles), an area almost the size of the United Kingdom. Total lives lost may finally easily exceed 2000, and damage to property has been estimated in the range $25 to $100 billion. The social and environmental impacts are impossible to cost.Some idea is given in NOAA space images.

There are now pressures to rebuild the wetlands south of New Orleans, as coastal wetlands can help to reduce the impacts of hurricanes and of the surges they generate. The disaster was anticipated by scientists running computer models, including SLOSH (see Box on page 153 of the book), but needed strengthening of levees was not undertaken, perhaps in part because of the very high estimated costs. For example, in 1998 a collection of State and Federal Agencies mad proposals for a $13 billion strategy to restore the Louisiana wetlands. Other researchers are considering whether the frequency and intensity of hurricanes will increase as a result of climate changes.

NOAA