Collection of High-Water Mark Data at Selected Roadway Crossings To Document October 2016 Flooding in the Pee Dee and Waccamaw River Basins of South Carolina

Science Center Objects

Hurricane Matthew generated large amounts of rainfall in South and North Carolina during September/October 2016. The South Atlantic Water Science Center, in cooperation with the South Carolina Department of Transportation, recorded High-Water Marks along selected road crossings, within the Pee Dee and Waccamaw River Basins of South Carolina.

Heavy rainfall occurred across South and North Carolina during a period from September 28, 2016 through October 10, 2016 as a result of tropical moisture from Hurricane Mathew (fig.1).  

Infrared satellite image of Hurricane Matthew rainfall amounts, 2016
Figure 1.  Infrared satellite image showing the amount of rainfall in South and North Carolina during the period from September 28 through October 10, 2016 (National Aeronautics and Space Administration https://www.nasa.gov/feature/goddard/2016/matthew-atlantic-ocean, NASA/JAXA, Hal Pierce).  The areas in purple show highest rainfall amounts.(Public domain.)
Map showing gage location on the Cape Fear River, NC
Figure 2.  Location of U.S. Geological Survey station 02105500 Cape Fear River at William O’Huske Lock near Tarheel, NC.(Public domain.)

The storm caused major flooding from the Northeastern areas of South Carolina (SC). Over 16 inches of rain fell on October 8, 2016 at an U.S. Geological Survey (USGS) precipitation gage 02105500 Cape Fear River at William O’Huske Lock near Tarheel, NC, which is located between Fayetteville and Lumberton near St Pauls, North Carolina (NC) (fig. 2).  U.S. Geological Survey streamgages recorded peaks of record at least at 5 locations in NC with two of those locations being on the Lumber River.  The Lumber River enters South Carolina approximately 6.5 miles upstream from Nichols, SC and merges with the Little Pee Dee River approximately 2.5 miles downstream from Nichols, SC (Fig. 2). 

Selected High-Water Marks along Pee Dee and Waccamaw Rivers, SC
Figure 3. S.C. Department of Transportation-selected high-water mark locations.(Public domain.)

As part of the statewide response to the flooding, the USGS and South Carolina Department of Transportation (SCDOT) conducted a cooperative study to collect high-water mark (HWM) data at 31 selected road crossings (fig. 3).  Figure 4 shows the heavy flooding that was observered along the Waccamaw River Basin near Conway, SC. U.S. Geological Survey personnel visited each site to flag and survey HWMs.  The crews flagged marks on both banks, upstream and downstream from bridges (four quadrants of each bridge).  Each mark was identified by a unique number, described, and rated for quality. High-water mark information was sought one bridge-width opening upstream from each bridge as well as at or near the downstream bridge exits.  If marks at these locations were not available, crews extended their search area several hundred feet further upstream or downstream as necessary. The horizontal coordinates (latitude and longitude) of each mark were determined by Global Positioning System (GPS) equipment relative to the North American Datum of 1983 (NAD 83), and the elevations of these marks were surveyed to North American Vertical Datum of 1988 (NAVD88).  At many sites, reliable HWMs were difficult to find because data collection began 3 weeks after the historic flooding, and subsequent rainfall events, wind, or anthropogenic activity had degraded or eliminated any distinct marks.   As a result, engineering judgment was used to estimate the peak water-surface elevations for each site or quadrant.  The location of the upstream peak elevation was estimated to be one bridge-opening width upstream from the bridge, and the downstream peak elevation was located at the bridge exit. 

The HWM elevations and descriptive data have been posted on the USGS Short-Term Network (STN) website.    The STN is a national-scale application and database designed to support USGS event-based sensor deployments and HWM data-collection efforts.  The URL for the STN website is https://stn.wim.usgs.gov/STNWeb/#/.  The Flood Event Viewer option can be used to inspect data for selected events, and menus at the STN Data Portal can be used to download data by event, state, and more. Please note that the STN uses functionality that is not completely supported by Internet Explorer; the preferred browser is Chrome.

Flooded Homes along Waccamaw River near Conway, SC
Figure 4. Flooding along the Waccamaw River near Conway, SC. Photograph by Dale Skipper U.S. Geological Survey, October 2016(Public domain.)