Using a global positioning system (GPS) unit no bigger than a blue crab, Doug Marcy has changed post-storm assessment and response in South Carolina.
Marcy, a NOAA Coastal Services Center fellow working with the South Carolina Office of Ocean and Coastal Resource Management (OCRM), has helped develop a system using GPS satellites and geographic information systems (GIS) to rapidly assimilate post-storm damage assessments.
The system will be used to quickly determine the extent of damage to homes, erosion control devices, and other structures along the immediate coast; it will be used to determine whether the structure can be rebuilt and, if so, where.
Joe Fersner is manager of engineering and state certifications for South Carolina OCRM. He said the agency is already using GIS to map the location of existing docks and as a reference when reviewing dock permits. The tool shows where docks are proliferating and where they are compared to natural habitats such as oyster beds.
"The primary place we're going to end up using it is for damage assessments after storms," Fersner said, "when we go out and have to look at structures. After Hurricane Hugo (in 1989) it was extremely difficult for us to figure out where we were. With GPS, it can hone us in on a location."
Being able to quickly determine which homes are destroyed, which are only damaged, or which need further study, is extremely important after a major storm. Property owners are demanding information; insurance adjusters are on the scene; and political, economic, and social decisions need to be made. "Knowing what's there on the beach before a storm hits is half the battle," Marcy said.
Battles such as this aren't cheap. Marcy said each orthophotographic map covers about 2,000 feet of shoreline and each picture costs between $800 and $900. The GPS/GIS project is only as good as its base information, meaning the maps and cadastral data need to be updated every few years.
A large amount of data is involved, from the cadastral information for the database to the GIS needed to create the maps.
Marcy scanned and geo-rectified aerial photographs of the beachfront using GIS software. Then, he overlaid the parcel information maps and location of the jurisdictional baseline and setback.
Using the hand-held GPS, he walked the beach in a test post-storm scenario, taking positioning readings adjacent to structures. This GPS data was processed in the office and uploaded to the GIS as a final graphically represented damage report. The report could then be plotted and used to make post-storm management decisions.
Each structure had been traced electronically and marked with a "centroid" point. Each centroid is linked to another database. By clicking on the centroid for a home, a database appears relating the tax map number for the structure, the owner's name, the appraised value, when it was built and on which photographic map it appears. There is a similar database for erosion control devices.
The map shows whether the existing structure is seaward or landward of the baseline and setback. In South Carolina, if a home or erosion control device is damaged to the extent that repairs would cost more than two-thirds of the value of the structure, it is legally considered to be destroyed.
In that case, a new structure must be built landward of the setback line without infringing on the road right-of-way.
For more information, contact Doug Marcy of South Carolina's OCRM at 803-744-5838.
