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Measuring Hurricane Impacts—USGS Coastal Hazards Team Is Up to the Challenge
The hurricane seasons of 2004 and 2005 continue to challenge and hone the skills of the U.S. Geological Survey (USGS)'s Coastal Hazards team in Florida, a part of the USGS National Assessment of Coastal Change Hazards project. The team's work is featured in an educational exhibit called "Into the Eye: Hurricanes" that opened October 13, 2005, at the Pier Aquarium in St. Petersburg, FL. The exhibit describes the team's ongoing studies of long-term coastal changes and the effects of extreme storms, with a focus on the destructive 2004 hurricane season, during which three hurricanes crossed Florida and one battered the Gulf Coast. While this exhibit was being finalized, along came the even more destructive storms of 2005. The 2005 hurricane season arrived earlier than expected on June 9, when Tropical Storm Arlene became the first named storm. By July 5, Dennis became the fourth named storm of the season, eventually growing to a category 4 hurricane and slamming the Florida panhandle with 120-mph winds. As Dennis headed north through the Gulf of Mexico, a massive red-tide bloom coinciding with storm surge stranded dead fish in the streets of downtown St. Petersburg, where the Coastal Hazards team is headquartered in the USGS Center for Coastal and Watershed Studies. Perhaps these events were a hint of the intensity of storms still to come in the 2005 hurricane season. By the end of September 2005, 17 storms had been named in the Atlantic Ocean and Gulf of Mexico, including five major hurricanes rated category 3 or higher on the Saffir-Simpson scale. The research team has responded to three major storms that made landfall in the United States—Hurricanes Dennis, Katrina, and Rita—forecasting likely coastal impacts as each storm approached, and documenting coastal changes as soon as possible after landfall. (As of this writing, on October 19, 2005, they are preparing for the possible impacts of Hurricane Wilma.) In this rapid-response mode, the team operates at a fast pace, with daily meetings to assure that their efforts are organized and on track. The team's numerous goals begin with a forecast of coastal inundation (flooding) based on tropical-weather advisories from the National Hurricane Center. After a storm makes landfall, crews book small aircraft to fly low-elevation missions over the affected areas, recording coastal impacts with digital video and photography. Partner organizations are contracted to fly lidar (light detection and ranging) surveys over the same areas in order to create high-resolution topographic maps, which allow researchers to quantify shoreline retreat, overwash, and other important indicators of coastal change. The 2004 and 2005 storm seasons have been remarkably similar, both producing multiple major hurricanes hitting Florida and the Gulf Coast. During both seasons, as soon as team members outlined a plan of action for addressing one storm, another appeared on the horizon. The 2005 season has been different, however, in the overwhelming amount of media and intergovernmental interest in the effects of Hurricane Katrina on the Louisiana and Mississippi coastlines. Certainly, Katrina has set a new standard for examining the natural and societal impacts of hurricanes; Rita, too, generated some drastic changes in coastal areas of Louisiana and Texas (for examples, see Hurricane Rita Impact Studies).
The USGS researchers coordinate with members of partner organizations, including Wayne Wright of the National Aeronautics and Space Administration (NASA) and Jeff Lillycrop of the U.S. Army Corps of Engineers, who fly lidar surveys of the affected coastlines. USGS team members BJ Reynolds and Nancy DeWitt set up Global Positioning System (GPS) base stations to provide navigational guidance for these surveys, often living out of government vehicles for lack of alternate housing. Within a few days, data from the lidar surveys are transmitted to the USGS office, where geographic-information-system (GIS) specialist Kristy Guy processes the data and creates GIS images of sediment erosion and accretion that are used to quantify coastal changes seen in the quick-response photography. These GIS images are posted online for public viewing (for example, Hurricane Rita Impact Studies and Hurricane Katrina Impact Studies). The scientific team then analyzes the lidar data for such indicators of coastal change as shoreline retreat, volume change, and change in island elevation. Longer-term goals include analyzing spatial variations in erosion patterns and improving the group's ability to predict which coastal regions are especially vulnerable to storm impacts.
Many challenges confront this group, including maintaining an ever-increasing library of video, photographic, and lidar data. Morgan, who is often tasked with the organization of data files, notes that "the volume of data we have collected in the past 2 years is beginning to overwhelm our storage space and processing limits, and we are starting to reassess these needs for upcoming seasons." Another challenge that faces the group is maintaining up-to-date surveys of coastlines that may potentially be affected by hurricanes. Baseline, or prestorm, lidar surveys are necessary to quantify the volume of erosion and accretion, and project chief Sallenger must keep informed of when each coastline was last surveyed so that he can determine when to fly new baseline surveys before the arrival of a major storm. Despite these challenges, the Coastal Hazards team has stayed on top of the details, providing valuable data for scientists, decisionmakers, and the general public. The project's Hurricane and Extreme Storm Web site features inundation forecasts, pairs of before-and-after photographs, quick-response photographs of entire coastal towns, and lidar images detailing the magnitude of coastal change. An important part of the team's work is to disseminate information within the scientific community. Stockdon presented the group's initial findings at the Geological Society of America meeting in Salt Lake City, UT, in October and will also cochair a special session on Hurricane Katrina at the American Geophysical Union Ocean Sciences meeting in Honolulu, HI, in February 2006.
The USGS has provided information and imagery to many media outlets, including the Web, television, and print. Many local and national news agencies have featured USGS images, and several have asked Sallenger to comment on the vulnerability of coastlines after the impacts of Katrina and Rita. National Geographic assembled three photomosaics with the descriptive title "Going, Going, Gone—Dauphin Island," showing the progressive erosion of the west end of the island after both Ivan (2004) and Katrina (2005) shifted the island landward (see Before and After Photo Comparisons of Dauphin Island). USGS images also have featured prominently in national newspapers, including the New York Times and USA Today. Asked to comment on rebuilding the Gulf Coast in one New York Times article, Sallenger responded, "there are some places where you should think twice about putting up a pup tent." The CBS Evening News picked up a video news release that showed post-Katrina aerial video footage from the Chandeleur Islands in eastern Louisiana. During the flight, USGS scientists onboard the plane were studying GPS data that told them they were above the Chandeleur Islands while seeing nothing below but open water. Lidar images later confirmed that the northern 3 mi of the island chain had been completely eradicated by the storm. The dialogue between Morgan and Krohn recorded on the video captures their confusion: Morgan: "I don't think that's it." Krohn: "According to the GPS, we're over the islands." [As the flight proceeds south, remnants of marshy outcrops appear where sandy beaches once lay.] Morgan: "Can you see some islands out there?" Krohn: "Something like islands." Morgan: "Okay, we've got pieces and parts here." Krohn: "Definitely run the tape, because that might be all of the islands." Pilot: "According to GPS we're over the Chandeleur Islands. They're right here." While data collection and processing move forward, the team will continue to analyze their findings, hoping to uncover long-term implications of coastal change produced during the past two hurricane seasons. It's a tall order, but this team is up to the challenge.
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in this issue:
Sonar Survey of Sea-Floor Habitats Drilling for Submarine Ground Water
USGS and Elementary School Receive Mayor's Top Apple Award
Chinese Delegation Visits USGS to Discuss Gas-Hydrate Studies
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U. S. Department of the Interior | U.S. Geological Survey
