THE INFLUENCE OF LAND-USE CHANGES ON DELTAIC SEDIMENTATION: AN EXAMPLE FROM THE NORTH CAROLINA COASTAL PLAIN

The Newport River system, situated entirely within Carteret County, North Carolina, is a small coastal-plain watershed approximating 210 km² in size. Its fluvial headwaters originate at an elevation of only 11 m, about 30 km landward of the system's bay-head delta. Maps of the late 1950s place the deltaic shoreline 100s of m landward of its present day location and illustrate an estuarine floor dominated by sand. Cores from the modern delta front show this sand overlain by several meters of soft, homogenous clay. A GIS-based study is underway to evaluate and explain sedimentary changes within the Newport bay-head delta in an effort to provide insight into the nature of responsible source-to-sink dynamics.

Aerial photographs taken periodically (about every 5 years) of the study area over the past 50 years were obtained from the United States Department of Agriculture (USDA) and the North Carolina Department of Transportation (NCDOT). The mapping software package ArcGIS 9.1 was used to georectify the photographs and characterize/quantify changes to the Newport watershed and delta, respectively. Urbanization and changes in the extent and type of agricultural land-use practices have occurred within the Newport watershed since the late 1950s. Averaged regional trends include increased urbanization, decreasing agriculture, and the installation of silviculture operations covering around 20% of the entire Newport drainage basin. A dramatic increase in the rate of delta shoreline advance coincides with the wide-scale stripping of vegetation along a major tributary to the Newport, suggesting a strong sediment contribution by this industrial practice.