Floodplain Sedimentation During an Extreme Flood: the 1999 Flood on the Tar River, Eastern North Carolina

• Published in: Physical geography Vol. 25; no. 4; pp. 334 - 346
• Main Authors: Lecce, Scott A., Pease, Patrick P., Gares, Paul A., Rigsby, Catherine A.
• Format: Journal Article
• Language: English
• Published: Abingdon Taylor & Francis Group 01.01.2004; Taylor & Francis
• Subjects: America; Bgi / Prodig; floodplain sedimentation; floods; Hurricane Floyd; Physical geography; United States of America; North Carolina; United States of America; Exceptional event; Flood; Sedimentation rate; Suspended load; Floodplain; Stream; Hurricane; Season; Sedimentation
• ISSN: 0272-3646; 1930-0557
• DOI: 10.2747/0272-3646.25.4.334

This study examines floodplain sedimentation following the largest flood in the 98-yr. record on the Tar River, North Carolina. Hurricane Floyd made landfall just 10 days after Hurricane Dennis in September 1999, bringing unprecedented rainfall (30-46 cm) and flooding to eastern North Carolina. A field survey of the lower 350 km of the river showed that this >500 yr. flood deposited very little overbank sediment (<1 mm) on most of the floodplain. We used suspended sediment concentrations measured on the Tar River from 1958-1967 to suggest that the seasonal timing and sequencing of flood events in 1999 are the most probable explanations for the minimal geomorphic impact of this extreme flood. The early autumn timing of the flood coincided with crops that were mature but not yet harvested, and when natural vegetation was very dense and effective at stabilizing channel banks, hillslopes, and floodplain soils. Hurricane Dennis may have exhausted the available sediment supply and transported this sediment to the Pamlico Sound before reaching flood stage, thereby reducing the sediment available to be transported and deposited by the flood that followed Hurricane Floyd.