Post-Dorian shoreline change at Cape Hatteras National Seashore: 2019 report

Baron, Lisa

doi:10.36967/nrr-2282127

In 2018 and 2019 the Southeast Coast Network (SECN), with assistance from park staff, collected long-term shoreline monitoring data at Cape Hatteras National Seashore as part of the National Park Service (NPS) Vital Signs Monitoring Program. Monitoring was conducted following methods developed by the NPS Northeast Coastal and Barrier Network and consisted of mapping the high-tide swash line using a Global Positioning System unit in the spring of each year (Psuty et al. 2010). Shoreline change was calculated using the Digital Shoreline Analysis System (DSAS) developed by the United States Geological Survey (USGS; Himmelstoss et al. 2018). Following the same field methods used for monitoring long-term shoreline change, geospatial data were collected as part of the Hurricane Dorian (or Dorian) Incident Response from September 12–16, 2019. This report summarizes the post-Dorian data and the previous two shoreline data collection efforts (spring 2019 and fall 2018). Key findings from this effort are below. Pre-and post-storm surveys of approximately 122.04 kilometers (75.83 miles) of shoreline indicate a geomorphologically dynamic beach/barrier island system response to a major storm system. Many areas of both accretion and erosion were noted in both the seasonal and annual shoreline change analyses performed. The mean seasonal shoreline change distance was positive (denoting accretion) for the seasonal analysis of Bodie and Hatteras Islands. When the data from all three islands area averaged, the mean annual shoreline change distance was negative (denoting erosion). The mean seasonal shoreline change distance on Ocracoke Island was also negative. In comparing the shoreline change on the three islands of Cape Hatteras NS, Ocracoke Island exhibited the most erosion on average. Overall, there appears to be a short-term trend in shoreline erosion during the 2018 to 2019 time period; however, the net impact to shoreline position from Dorian was minimal along the ocean facing beaches. There was a large amount of shoreline change in areas near inlets. Of the park facilities analyzed for potential impacts of future storms, seven buildings were identified within 25 meters (82 feet) of the post-Dorian shoreline and twenty-three buildings within 100 meters (328 feet)

Post-Dorian shoreline change at Cape Hatteras National Seashore: 2019 report

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