Migration to a Geospatial Database to Improve Data Management In the N.C. Geological Survey's Landslide Hazard Mapping Program

In 2005, the North Carolina General Assembly tasked the North Carolina Geological Survey to produce landslide hazard maps for 19 western N.C. counties impacted by Hurricanes Frances and Ivan. Currently, Macon and Watauga Counties are complete and fieldwork is underway in Buncombe County. Landslide data are maintained in a 100+ attribute Microsoft Access database with over 5,200 entries. After data entry and editing, the database is converted into a GIS point shapefile. The associated landslide features (debris deposits, landslide tracks and scarps) are created directly in ArcGIS through aerial photography interpretation, analyzing landslide deposit signatures using LiDAR (light detection and ranging) digital elevation data, and field verification of selected features. The spatial resolution of these shapefiles meets or exceeds the 1:24,000 mapping accuracy standard.

The mapping has produced more than 2,100 km² of detailed information – equivalent to fourteen 1:24,000-scale quadrangles. Depending on the amount of landslide activity in the area, each county requires 10 – 40 GB of storage consisting of large raster datasets. These include several vintages of scanned and georectified aerial photography, high-quality post-storm digital orthophotography, and numerous LiDAR-derived rasters used in the debris flow susceptibility modeling.

To meet an aggressive schedule, we are streamlining our current database management system and workflow to improve field and office efficiency. The program is migrating toward an ArcSDE geodatabase where data will be entered in the field using handheld GPS devices, edited by multiple users simultaneously in the office, and seamlessly incorporated into the GIS-based mapping. The geodatabase will consist of primary files (i.e., landslides, deposits, tracks, etc.) linked together through related tables. Large raster datasets and the geodatabase will be maintained on a shared server linked with our departmental IT server in Raleigh to improve data sharing and reduce data duplication.