The flooding of New Orleans by Hurricane Katrina provides many lessons for the environmental and engineering communities and raises serious public policy questions about risk management. Although serious environmental and waste management concerns were highlighted as a result of the flooding, many were not observed in the extensive environmental sampling that occurred. The potential environmental consequences were of concern because of the many chemical plants, petroleum facilities, and contaminated sites, including Superfund sites, in the areas covered by floodwaters. The potential sources of toxics and environmental contaminants included metal-contaminated soils typical of old urban areas. Compounding these concerns is the presence of hazardous chemicals commonly stored in households adn commercial establishments and the fuel and motor oil in approximately 350,000 flooded automobiles. Uncontrolled biological wastes from both human and animal sources also contributed to the pollutant burden. There were concerns associated with the immediate impacts of the flooding, the disposal of the debris and wastes in the aftermath, as well as the long-term legacy associated with contaminants in homes and yards. This discussion focuses on successes and failures in responding to each of these concerns as well as lessons learned for future disasters. Special attention is paid to some of the unique hazards posed by Katrina, including airborne contaminants associated with disposal, high indoor concentrations of contaminants due to fractionation from outdoor soils, and mold.