Landsat Thematic Mapper-Derived Estimates of Marsh Cover and Vulnerability in Terrebonne, Barataria, and Breton Sound Basin Marshes, Southeastern Louisiana: Clear-sky Data Sets, 1984-2011

Twenty-five georeferenced sets of images and maps estimating marsh vegetation cover and vulnerability were derived from Landsat Thematic Mapper (TM) Path 022 and Rows 039 and 040 digital number data sets collected between 1984 and 2011 for a time-series analysis to evaluate the effect of the Deepwater Horizon oil spill (April 20 - September 19, 2010) on the Terrebonne, Barataria, and Breton Sound basin emergent marshes. Fourteen datasets were classified as clear-sky (UDI R4.x264.000:0049), ten as cloudy-sky (UDI R4.x264.000:0050) and one dataset containing the September 2, 2009 clear-sky dataset that as a three to four pixel-wide line of missing data located over the southern Terrebonne and Barataria marshes (UDI R4.x264.000:0051). The projection is the Universal Transverse Mercator (UTM Zone 15 North). The file format is georeferenced ENVI data (.dat) and header (.hdr) files. Surface reflectance values were used to calculate the Normalized Difference Vegetation Index (NDVI), the Normalized Difference Water Index (NDWI), and the Normalized Difference Vegetation Index (NDSI) for each Normalized Difference Composition (NDXI) clear-sky data sets. Linear spectral unmixing of the three stacked normalized difference indices data sets (NDXI) with image-derived spectral endmembers of marsh vegetation, water, and marsh substrate/soil derived from the composite NDX data sets were used to estimate of the percentage of marsh vegetation, water, and marsh substrate for each marsh pixel in the Terrebonne, Barataria, and Breton Sound basins. The classified maps consist of three classes: (1) non-marsh or unclassified pixels have a value of 0 and are black; (2) pixels with 40% or less vegetation have a value of 1 and are black or gray; and (3) pixels with more than 40% marsh vegetation or are classified as intact marsh. Intact marsh pixels have a value of 2 and are white. Additional masks were used to estimate the percentage of intact marsh area in four twenty-km wide zones oriented roughly parallel to the coast and twelve three-km wide segments located immediately adjacent to the gulf waters in Terrebonne Bay, Barataria Bay and Breton Sound. The four zones and twelve coastline segments were used to evaluate the effects of Deepwater Horizon oil spill and sea level rise on the Terrebonne, Barataria, and Breton Sound basin emergent marshes.