Effects of Hurricanes on the Gulf Coast ecosystems: A remote sensing study of land cover change around Weeks Bay, Alabama

N. S.N. Lam, Louisiana State University
K. B. Liu, Louisiana State University
W. Liang, Louisiana State University
T. A. Bianchette, Louisiana State University
W. J. Platt, Louisiana State University


Climate change effects such as accelerated sea-level rise and increased hurricane activity threaten ecosystems such as along the Gulf of Mexico coast. Although sea-level rise is a relatively slow process that may allow more time to prepare and adapt, hurricane strikes are short-term, brief events that generate immediate as well as long-term effects on coastal ecosystems that could be devastating. An accurate assessment of the effects of hurricane strikes on the coastal ecosystems would be useful to policy development designed to mitigate impacts. This paper compares the land cover change around Weeks Bay, Alabama, USA following landfalls of Hurricanes Ivan and Katrina (September 16, 2004 and August 29, 2005). Two high-resolution IKONOS imagery dated immediately after Ivan and 15 months after Katrina were compared. A hybrid supervised and unsupervised image classification method that included all five bands in the images, plus the NDVI band, was employed to identify seven land cover classes from the two images. The results show that "fresh marsh" had the largest relative percent decrease (-52%) in acreage. "Brackish marsh" and "swamp" also had a small decrease in acreage, -9.8% and -9.6%, respectively. On the other hand, "Forest" gained 6.94%. These differential rates of loss and gain in land cover after repeated hurricane strikes can be used to evaluate the resiliency of the ecosystems. With more studies and verification, these rates can be used in future predictive modeling and for assessment of loss of ecosystem services due to hurricanes.