Visit ParkNet NPS Geographic Information Systems National Park Service, U.S. Department of the Interior
[Go Back]

Habitat Analysis and Road Relocation Following Hurricane Opal

Gulf Islands NS
Riley Hoggard
In October 1995, the section of Gulf Islands National Seashore located on Santa Rosa Island was battered by Hurricane Opal’s sustained winds of 125 mph and 15 foot storm surge. Numerous park structures were heavily damaged and most of the 7-mile park road through the Santa Rosa Area was destroyed. Impacts to the natural environment included severe shoreline recession, razed sand dunes, filled wetlands, and a general loss, albeit temporary, of island habitat.

In an effort to document storm impacts, plan for habitat restoration, and rebuild the park infrastructure, the landscape features and damaged structures were mapped using differentially corrected GPS exported to ArcView shapefile format. Resource data was collected for surviving wetlands and sand dunes and new overwash fans (sand pushed across the island by the storm surge).

Barrier islands are dynamic geological features and change in location and configuration in response to normal ocean currents and storm impact. With storms such as Hurricane Opal, islands will move toward the mainland as they literally “roll over” themselves. Spatially, the post-hurricane island was located 200 feet closer to the mainland than the pre-hurricane island in certain areas. The entire length of the gulf beach receded by as much as 150 feet.

It was decided that Hurricane Opal offered a perfect opportunity to re-evaluate the original placement of the park road. Constructed just landward of the primary dunes, the road impeded the natural growth and migration of the dunes, fragmented important dune habitat, and disrupted development of the secondary dune system. The GIS mapping provided the tool to analyze relocation of the road whereby wetlands, dunes, and undisturbed habitat could be avoided and adequate environmental benefit could be realized. Demonstrating environmental (and economical) benefit was paramount to convincing the Federal Highways Administration to spend the additional funds to relocate the road. The GIS maps provided the perfect graphical representation of the proposal and helped convince the decision-makers.

Approximately 3 miles of the 7-mile road were relocated as a result of this analysis. Subsequently, almost 8 years later, these data are again being analyzed to help prepare for future hurricanes. Coupled with island recovery data, these data are being used by a geological student from Louisiana State University, as part of the Geoscientist-in-Park program, to prepare a hurricane recovery plan. This plan will identify sites prone to storm overwash and construction techniques/locations prone to storm damage, features to be avoided during future reconstruction efforts. The project is currently in progress.
April 08, 2004