The utility of geographic information systems (GIS) in rapid epidemiological assessments following weather-related disasters: Methodological issues based on the Tropical Storm Allison experience

Flooding is the most common natural disaster worldwide, and is the leading cause of weather-related deaths in the United States. Tropical storm Allison hit landfall near Galveston, Texas on June 5, 2001, causing the most severe flood-related damage ever recorded in the Houston metropolitan area. This devastating storm dumped 37 in of rain in 24 h on parts of the city, killing 22 people and causing more than $5 billion in damage. The main goal of the public health response to tropical storm Allison was to rapidly evaluate the immediate health needs of the community. Geographical information system (GIS) technology was instrumental to the timeliness of this effort. We conducted a rapid needs assessment in the areas most affected by flooding using modified cluster sampling facilitated by GIS methodology. Of the 420 households participating in the survey, we found a significant increase in illness (OR, 5.1; 95% CI, 2.7-9.4), injuries (OR, 4.8; 95% CI, 1.9-12.8), and immediate health needs (OR, 3.3; 95% CI, 1.7-6.1) among persons living in flooded homes compared to non-flooded homes. There were 60 households reporting serious damage, 24 of which were outside the 500-year flood plain. We also obtained reliable estimates of the extent of damage and household needs to help guide relief efforts. These findings underscore the usefulness of rapid needs assessment as a tool to identify actual health threats and to facilitate delivery of resources to those with the greatest and most immediate need. Our ability to swiftly plan and implement a rapid needs assessment over a large geographical region within 1 week following the damage would not have been possible without the utilization of GIS methodology and the availability of skilled personnel and timely data resources.