Mapping long-term habitat and shoreline changes at Jean Lafitte National Historic Park and Preserve

Handley, Larry

Hurricanes Katrina and Rita caused extensive shoreline erosion and marsh loss in Louisiana. Preliminary estimates by USGS using LANDSAT analysis indicated perhaps 100 mi^2 (26,000 ha) may have been lost (Barras et a]), 2005). Though most of this loss occurred east of the Mississippi River, the storm impact was clearly evident over 100 miles west of New Orleans along the Isles Derniers barrier islands in Terrebonne Parish and from Hurricane Rita shoreline erosion was observed from New Orleans west to the Bolivar Peninsula in Texas. The combined wave action, storm surge, and high winds of both hurricanes affected the Barataria Unit of Jean Lafitte National Historic Park and Preserve (JELA) by eroding the shoreline and canal banks, pushing salty water and wrack into the interior marsh and toppling large numbers of trees throughout the Unit. Interpreting and mapping the recent impacts of the 2005 hurricane season on JELA and comparing that to interpretation and mapping from 2004 imagery has provided direct, quantitative measures of shoreline change and other impacts of the hurricanes. These data continue the long-term sequence of maps of JELA already produced by NWRC that provide information concerning important trends at the park. The addition of two more dates, shortly before and immediately after Hurricane Katrina, document effects of recent stabilization methods as well as long-term shoreline and habitat trends at the JELA from 1958 to 2005. The Barataria Unit of the park has been mapped by NWRC using National Wetlands Inventory (NWI) classification for the years 1958, 1978, 1988, and 1998. This series provides a consistent classification method over a 40 year span. During that 40 years many hurricanes have come and gone. Oil exploration and various pipeline canals have been dug. Also, fire frequencies have decreased over the years. Many of these changes have had effects on the habitats mapped at the Barataria Unit. Habitat maps from recently acquired aerial photography extend that sequence into 2005. Since the 1998 mapping, 1:40,000 color infrared aerial photography was acquired in 2004 and again, after the hurricanes in 2005. Tight bracketing in time by these two dates of photography provided the park with the best possible photographic and mapping information concerning the impact of tropical weather systems on the park. Given that current climatic forecasts are accurate that indicate more frequent, high-intensity storms will occur for the next 10-50 years, understanding the impact to the park of strong tropical systems is of critical importance.