Hurricane Katrina was one of the most intense and costliest hurricanes to hit the United States. On August 28, 2005, Katrina was a category 5 storm (on the Saffir-Simpson scale) in the middle of the Gulf of Mexico. It made landfall the next morning as a strong category 3 storm with sustained winds of 125 miles (200 kilometers) per hour.
Flooding in New Orleans began early that morning, and water continued pouring into the city until September 1. State health departments estimate that Hurricane Katrina caused about 2,000 deaths, most occurring in Louisiana. About 75 percent of the New Orleans metropolitan area was flooded. The storm caused an estimated $80 billion in damage.
Landsat recorded the devastation and continues to monitor the region’s wetlands. New Orleans, Louisiana, is near the bottom of the images along the Mississippi River. The city lies just south of Lake Pontchartrain. Hundreds of square miles of wetlands were lost after Katrina. Some marshlands became permanent water bodies. Some projects now aim to bring back marshlands because of their value in defending the coastline from storms.
(Black stripes run through the Sep. 15, 2005, images because of the Scan Line Corrector failure on Landsat 7 in May 2003.)
Lake Pontchartrain covers the northern part of these Landsat images. The curvy dark line is the Mississippi River as it meanders past New Orleans. The dark straight lines are canals, built for flood protection and as an aid to water navigation.
The September 7 image shows New Orleans days after Hurricane Katrina struck. The flooded areas are dark, giving the city a bruised appearance. A straight vertical line separates a dark flooded area of the city from the light green-pink unflooded area. The floodwaters appeared to have stopped at the 17th Street Canal. This canal failed but the west dike held, keeping that part of the city from flooding.
Floodwater from the Gulf of Mexico made its way to Lake Pontchartrain, which then flooded this part of the city with an 11-foot storm surge. Water entered the canals but the canal walls did not overtop. The walls failed when water had only risen part of the way up the wall. When these canals broke, water from Lake Pontchartrain poured into these neighborhoods.
By September 7, the city had started to drain. Pumps worked to return the water to Lake Pontchartrain. About 380 cubic meters (100,000 gallons) of water were pumped out of the city every second.
Green vegetation has returned by the 2006 image, one year after the storm. Comparing the image from before Katrina and the most recent 2014 image, the amount of vegetation appears similar.
The Mississippi River Gulf Outlet (MRGO) was built in the 1950s and 1960s as a shorter shipping route from New Orleans to the Gulf of Mexico. The 76-mile (122-kilometer) ship channel runs from northwest to southeast across these images. MRGO was one of the first levees to fail and flooded the neighborhoods visible in the upper left of the images. Sections of the MRGO levees crumbled early in the morning of August 29.
Notice how MRGO and other levees to the north form a < shape. Floodwaters from the Katrina storm surge funneled along this route and into the city. A short time later, a second line of levees meant to protect St. Bernard Parish failed and floodwaters quickly filled those neighborhoods.
The funnel effect amplified the storm surge by 20 to 40 percent. The resulting catastrophic flooding hit St. Bernard Parish and the Lower 9th Ward of New Orleans.