Since Hurricane Katrina was a weather-related event, it might be useful to check into the web sites for some of the key meteorological organizations that played some part in the story. They will have both background information and follow-up reports on the storm and its effects.
If you need numeric data related to Hurricane Katrina or weather in general, please contact the Research Computing Lab in Brown Library, the Scholars' Lab in Shannon Library and/or the Climatology Office in the Department of Environmental Sciences in Clark Hall. The Climatology Office maintains a web page at http://climate.virginia.edu/