Two Months of Flooding in Eastern North Carolina, September - October 1999: Hydrologic Water-Quality, and Geologic Effects of Hurricanes Dennis, Floyd, and Irene

WRI 00-4093
By Jerad D. Bales, Carolyn J. Oblinger, and Asbury H. Sallenger, Jr.

SIDEBARS

• Hurricanes in North Carolina
• Flood recurrence intervals
• Nitrogen and phosphorus in surface waters
• Waterborne pathogens
• Pesticide contamination of surface waters

FIGURES

1. Number of tropical cyclones, by type, making landfall in North Carolina, 1890-1999
2. Satellite image of eastern North Carolina with generalized basin outlines and tracks for Hurricanes Dennis, Floyd, and Irene, September-October 1999
3. Rainfall in North Carolina, September 4-5, 1999, during passage of Hurricane Dennis and locations of selected raingages in eastern North Carolina
4. Rainfall in North Carolina, September 14-16, 1999, prior to and during the passage of Hurricane Floyd
5. Generalized tracks of Hurricanes Connie, Diane, and Ione, August-September 1955
6. August 1955 and September 1999 monthly rainfall at selected sites in the Tar-Pamlico, Neuse, and Cape Fear River Basins, and at selected other sites
7. Site locations and flood recurrence intervals for September-October 1999 flooding at selected streamgaging sites in North Carolina and Virginia
8. Stage hydrograph for the Tar River at Tarboro, September-October 1999
9. Stage hydrographs for the Neuse River at Kinston, September-October 1999, and near Goldsboro, September-October 1996 and 1999
10. Streamflow in the Neuse River at four locations between Falls Dam and Kinston, September-October 1999
11. Annual peak flows, Tar River at Tarboro, 1897-1999
12. Annual peak flows, Neuse River at Kinston, 1928-1999
13. Sites at which water-quality samples were collected by the USGS in September-October 1999, following Hurricane Floyd
14. Densities of E. coli and C. perfringens bacteria collected near peak streamflow from Hurricane Floyd flooding, September 17-22, 1999
15. Cumulative total nitrogen load at sites near the mouths of the Tar, Neuse, Cape Fear, Northeast Cape Fear, and Lumber Rivers
16. Cumulative total nitrogen load at selected Neuse River sites in floodwaters from Hurricanes Floyd (1999) and Fran (1996)
17. Cumluative total nitrogen load at selected Tar and Cape Fear River sites in floodwaters from Hurricanes Floyd (1999) and Fran (1996)
18. (A)Nitrogen and (B)phosphorus yields at selected sites in floodwaters from Hurricanes Floyd (1999) and Fran (1996)
19. Cumulative total phosphorus load at sites near the mouths of Tar, Neuse, Cape Fear, Northeast Cape Fear, and Lumber Rivers
20. Near-surface and near-bottom salinity measured at Pamlico River at Light 5 during August-November 1999
21. Near-surface and near-bottom salinity measured at Pamlico River at Light 5 during October-November 1999
22. Near-surface and near-bottom dissolved oxygen concetration at Neuse River at Marker 38 at New Bern, October 1999
23. Locations at which shoreline change and overwash were documented
24. Aerial photographs showing storm wave overwash along N.C. Highway 12 north of Buxton, N.C., September 8, 1999
25. Photograph showing the former location of N.C. Highway 12 near Buxton and replacement dunes
26. Cross-shore profiles obtained using laser altimetry of the area north of Buxton where N.C. Highway 12 was destroyed
27. Photograph showing houses standing in the surf at Rodanthe, N.C.
28. Post Hurricane Dennis topography using laser altimeter data of an area near Rodanthe, N.C.

TABLES

1. Rainfall amounts in North Carolina associated with Hurricanes Dennis, Floyd, and Irene, September-October 1999; Hurricane Fran, September 1996; and annual average rainfall at selected locations
2. Maximum observed 12-hour and 24-hour rainfall at Rocky Mount and Kinston, N.C., during Hurricane Floyd, September 15-16, 1999, and 100-year rainfall statistics for eastern North Carolina
3. Hurricane Floyd information for selected streamgaging stations in North Carolina and Virginia
4. Effect of a period of record on computed 100-year flood magnitude, Tar River at Tarboro and Neuse River at Kinston, N.C.
5. Estimated monthly mean freshwater flow from basins draining to Pamlico Sound, N.C., September and Ocotober 1999
6. Summary of floodwater-quality samples collected in eastern North Carolina, September - October 1999
7. Dissolved oxygen concentrations at selected sites in the Neuse and Cape Fear River Basins, N.C., approximately 5 days following the passages of Hurricanes Floyd (1999) and Fran (1996)
8. Summary of water-quality samples collected during 1990-99 at selected sites in eastern North Carolina, and maximum concentrations measured following Hurricane Floyd, September - October 1999
9. Concentrations of selected pesticides detected in samples of Hurricane Floyd floodwaters from eastern North Carolina, September 16 - October 5, 1999

CONVERSION FACTORS, VERTICAL DATUM, SPECIFIC CONDUCTANCE, AND TEMPERATURE

Sea level: In this report, "sea level" refers to the National Geodetic Vertical Datum of 1929 (NGVD of 1929), a geodetic datum derived from a general adjustment of the first-order level nets of both the United States and Canada, formerly called Sea Level Datum of 1929.

Specific conductance: is given is microsiemens per centimeter at 25 degrees Celsius (µS/cm at 25°C).

Temperature: Water temperature is given in degrees Celsius (°C), which can be converted to degrees Farhenheit (°F) by using the following equation: