Collection of Historic Live-Bed Scour Data at Selected Bridges in South Carolina Using Ground-Penetrating Radar

The U.S. Geological Survey (USGS) in South Carolina, since 1996, has been using historic scour data collected from field investigations to develop regional envelope curves for clear-water abutment, contraction, and pier scour. The USGS is currently collecting historic live-bed scour at selected sites in South Carolina with the goal of developing similar regional envelope curves for live-bed scour. The collection of historic scour data is relatively simple for clear-water scour because the scour holes do not refill. The measurement of historic live-bed scour, however, can be problematic because of the partial or total refilling of scour holes by channel sediment. To address this problem, a geophysical technique, ground-penetrating radar (GPR) can be employed to assess buried scour surfaces. Starting in 2005, the USGS has used GPR to collect measurements of historic live-bed contraction and pier scour at 56 bridges in South Carolina. While there are limitations and uncertainty associated with scour measurements made with GPR, the data should yield valuable insights into regional trends of live-bed contraction and pier scour in South Carolina.