AVHRR IMAGERY USED TO IDENTIFY HURRICANE DAMAGE IN A FORESTED WETLANDOF LOUISIANA

Certain events provide a unique opportunity to test the monitoring cap ability of AVHRR imagery. On 26 August 2992, Hurricane Andrew passed t hrough Louisiana, impacting a large area of forested wetlands. One res ponse to the widespread defoliation resulting from the hurricane impac t was an abnormal bloom of new leaves and new growth in the underlying vegetation between September and October. To capture this atypical ph enology, a time sequence of AVHRR images was transformed into a normal ized difference vegetation index, NDVI, as an indicator of vegetation changes in the forest impacted by the passage of a hurricane. Using ge ographic information system functions, three sites in the impacted for est were vectorized as polygons, and the inclusive pixels were extract ed for subsequent graphical and univariate statistical analysis. Tempo ral curves of mean NDVIs for the three sites for before, during, and a fter the hurricane passage, and aggregate curves of the impacted fores t to an undisturbed forest, were compared. These comparisons corrabora ted the atypical phenology of the impacted forested wetland and direct ly related the cause to the hurricane passage.