Initially it was hoped that New Orleans had weathered the worst of Katrina, but within hours of the storm passing, it emerged that several key levees had been breached, causing floodwater to pour into the low-lying city.
By 31 August, an estimated 80% of New Orleans was underwater. The situation quickly deteriorated as it became apparent that thousands of people had been unable to evacuate or chosen to stay put.
Many took refuge in the city's Superdome, but without sanitation or proper supplies, conditions inside the crowded, overheated stadium became increasingly unbearable. Law and order across the city broke down, with reports of widespread looting and violence.
On 2 September a series of huge blasts, apparently at a chemical plant near the French Quarter, rocked the city. Large fires also broke out in several other districts.