T123 Sediment in Fluvial Systems: Production, Transport, and Storage at the Watershed Scale I

Sunday, 5 October 2008
8:00 AM - 12:00 PM

Effects of Climate and Land-Use Change on Sediment Delivery to a Small Coastal-Plain Estuary: A Look at the Newport River Bay-Head Delta

Paper number: T123-2
Program: Technical Sessions
Time: 8:05 AM – 8:20 AM

Authors

Abstract

The Newport Watershed encompasses 210 km2 of the lower North Carolina Coastal Plain and drains low-lying coastal croplands (1-2 m in elevation), slightly elevated areas of urban development (2-3 m in elevation), and a silviculture operation (1-2 m in elevation). The silviculture operation occupies around 20% of the total watershed and is situated in close proximity to the system's bay-head delta. Previous work has identified a recent shift from sand- to clay-dominance in the delta front. Aerial photographs of the river basin and delta (from NCDOT and USDA sources), sedimentation-rate curves (based on 210Pb analysis on select pushcores), and precipitation records (from a station within the catchment area) are evaluated in a GIS-based project to help explain the nature of source-to-sink dynamics and help identify sediment pathways and possible transport mechanisms.

Aerial photographs show that the Newport Bay-head Delta has prograded at a non-linear rate since 1958. A sudden increase in the rate of delta-shoreline advance is recognized to have occurred between 1964 and 1967, coinciding with the onset of silvicultural practices (road construction and initial deforestation) and a period of increased storminess (i.e. high precipitation and runoff). Sedimentation rates calculated for a pond within the installation are also marked by an increase during this time period. Since the establishment of the silviculture operation, subsequent episodes of delta progradation seem to coincide more closely with periods of increased storminess.

Although erosion can be expected to increase during periods of deforestation, sediments within the silvicultural installation are not mobilized until high-energy discharge events occur.