Comparison of classified Landsat Thematic Mapper (TM) satellite imagery acquired before and after the landfalls of Hurricanes Katrina (August 29, 2005) and Rita (September 24, 2005) demonstrated that water area increased by 217 mi2 (562 km2) in coastal Louisiana. Approximately 82 mi2 (212 km2) of new water areas were in areas primarily impacted by Katrina (Mississippi River Delta basin, Breton Sound basin, Pontchartrain basin, Pearl River basin), whereas 117 mi2 (303 km2) were in areas primarily impacted by Rita (Calcasieu/ Sabine basin, Mermentau basin, Teche/Vermilion basin, Atchafalaya basin, Terrebonne basin). Barataria basin contained new water areas caused by both hurricanes, resulting in some 18 mi2 (46.6 km2) of new water areas. The fresh marsh and intermediate marsh communities' land areas decreased by 122 mi2 (316 km2) and 90 mi2 (233.1 km2), respectively. The brackish marsh and saline marsh communities' land areas decreased by 33 mi2 (85.5 km2) and 28 mi2 (72.5 km2), respectively. These new water areas identify permanent losses caused by direct removal of wetlands. They also indicate transitory water area changes caused by remnant flooding, removal of aquatic vegetation, scouring of marsh vegetation, and water-level variation attributed to normal tidal and meteorological variation between satellite images. Permanent losses cannot be estimated until several growing seasons have passed and the transitory impacts of the hurricanes are minimized. The purpose of this study was to provide preliminary information on water area changes in coastal Louisiana acquired shortly after both hurricanes' landfalls (detectable with Landsat TM imagery) and to serve as a regional baseline for monitoring posthurricane wetland recovery.
