A GIS APPROACH TO ESTUARINE SHORELINE EROSION: CEDAR ISLAND, NORTH CAROLINA

Global warming and sea-level rise are a growing concern. Understanding shoreline response to these ongoing processes is valuable. Numerous studies have focused on ocean shoreline processes and estuarine shoreline change in different portions of the NC coastal system. This study uses a geographic information system (GIS) to analyze detailed changes in the estuarine shoreline within the Cedar Island area, a vast Juncus roemerianus marsh within the Albemarle Pamlico Estuarine System.

Geo-referenced aerial photography is used to calculate the shoreline change rate over a four decade time period, from 1958 to 1998. Shorelines were digitized along the water/land interface from geo-referenced aerial photographs and change rates were calculated from the shoreline distance movement over the four decade period. ArcGIS software and readily available datasets were utilized to evaluate factors hypothesized to influence erosion (i.e., elevation, land cover, fetch, wave energy). The average topographic elevation was calculated from digital elevation model data. Land cover type was determined using the 1997 NOAA Coastal Change Analysis Program dataset. Fetch and wave energy were calculated with a wave exposure model. Once calculated, the relationship between these parameters and the shoreline change rate was analyzed.

From the calculated data, the mean erosion rate in the study area is -0.24 m yr^-1, and it ranges from -2 m yr^-1 to 2 m yr^-1. The majority of shoreline within the study area consists of estuarine emergent wetland and low sediment bank with evergreen forest and scrub/shrub cover. The average shoreline change rates of the three most abundant land cover types are determined to be significantly different. Further analysis is underway to discern the relationships and trends of the additional variables effecting shoreline change.