The New York Times

As emergency management authorities struggled to help thousands of flood victims recover, Louisiana surveyed the scale of the disaster.

Using everything from hand-drawn maps and 911 reports to radar data and sophisticated mapping software, geographers at Louisiana State University have produced a preliminary atlas of the flood across two dozen parishes in the state.

In some parishes with more resources, the maps show fine detail. Others are still rough. “In many parishes, they are trying to establish basic services for their people,” said Brant Mitchell, director of the Stephenson Disaster Management Institute at L.S.U. “They are not focused on extents.” He said that some parishes, like Ascension, where flooding was widespread, have not yet produced maps. Ascension’s flooding was estimated from 100-year flood maps from FEMA.

Using Blackouts to Map Flooded Areas

Satellite photos of southeast Louisiana show damage to the electric grid during the storm. The images were released by NASA at the request of the Federal Emergency Management Agency and are used to determine power outages in order to map impact zones.

Assessing 140,000 Homes

The Baton Rouge Area Chamber has used the maps to estimate that more than 140,000 homes in the metropolitan area were in flood areas and could have been affected. Livingston and East Baton Rouge parishes appear to have suffered the most damage.