HARPER, Stephen B. and SPRUILL, Richard K., Department of Geology, East Carolina University, Greenville, NC 27858, harpers@mail.ecu.edu.
Four rainfall
events in the months of September-October 1999 triggered unprecedented
levels of upstream flash flooding in the tributaries of the Tar River and
downstream flooding in the lower portions of the Tar River Basin. These
rainfall events were Hurricane Dennis (6-9 inches) in early September,
Hurricane Floyd (9-15 inches) in mid September, a non-tropical storm-related
rainfall event (2-6 inches) in late September, and Hurricane Irene (3-9
inches) in mid October. The most intense flash flooding and prolonged downstream
flooding resulted from the rainfall generated by Hurricane Floyd.
Tributaries
to the Tar River experienced flash flooding in response to all four rainfall
events. The flood peaks for Fishing Creek and Conetoe Creek, resulting
from Hurricane Floyd, exceeded the historical high stages of 19.60 and
15.50 feet respectively for these two locations. Hardee, Green Mill, and
Chicod Creeks in the Greenville area experienced similar magnitudes of
flash flooding and also experienced back water flooding near their confluences
with the Tar River.
On the Tar
River flood peaks generated by Hurricane Floyd exceeded all previous historically
recorded flood events at Rocky Mount, Tarboro, and Greenville, NC. by 5.78,
7.51, and 5.22 feet respectively. The locations along the Tar River with
the highest flood peaks corresponded spatially to the areas of highest
rainfall. Rocky Mount, Tarboro, and Greenville, all of which experienced
10-18 inches of rainfall, also experienced the highest flood peaks relative
to any previously recorded flood events. The correspondence of total rainfall
amounts and peak levels of flooding and the cumulative flood impact from
rainfall from Hurricanes Floyd and Dennis suggest that the extreme magnitude
of the flooding along the Tar River and its tributaries resulted from unusual
meteorological conditions.
The Tar River
at Tarboro and Greenville remained in flood stage from September 09 and
10 to October 07 and 09 and crested on September 20 and 21 respectively.
Rainfall from Hurricane Irene renewed downstream flooding on the Tar River
at Tarboro from October 19-27 and at Greenville from October 19-29.