ASSESSING TORNADO DAMAGE VIA ANALYSIS OF MULTI-TEMPORAL LANDSAT 7 ETM+ DATA

On June 18, 2001 a powerful (F-3) tornado struck the village of Siren and other parts of Burnett County in northwestern Wisconsin, leaving a multi-million dollar swath of destruction more than 40 km long through a heavily forested area. This storm resulted in three deaths, eight serious injuries, complete destruction of 147 homes and damage to 451 others. Very shortly after the tornado, investigators at the University of Wisconsin-Madison obtained Landsat-7 imagery (from May 18 and June 19, 2001) and used a multitemporal principal components analysis (PCA) technique to produce change maps of the areas affected by the tornado. The Landsat imagery from both dates along with the change-assessment data, were reprojected and processed to suit the needs of the state and local emergency management team. Results were quickly distributed to emergency management staff over the Internet. Four days after the tornado, 1:10,000 normal color photographs were also acquired over the entire damage path. These have been used as reference data to assess the nature and accuracy of the damaged areas delineated by the above change detection methods as damaged. The satellite-based analysis has proven to be remarkably accurate and in many respects superior to information extracted from the aerial photography, in large measure due to the importance of the mid-IR ETM+ Band 5 data used in the multitemporal analysis. Thus, Landsat-7 data proved to be a very effective means of documenting the tornado damage and in aiding recovery efforts