Coastal Erosion on Bald Head Island, NCMidshipmen 1/C Grace Zagaja and Sophie Gatzounas, General Science

Professor Peter L. Guth, Oceanography Department

UNITED STATES NAVAL ACADEMY

Abstract

References

Conclusion

Results

Methods

Background

Acknowledgements

Coastal erosion is extremely prevalent along the coast of North Carolina impacting the beaches along with the vegetation, homes and businesses. Lidar data shows just how much the coastline of Bulk Head Island has shifted in the last 20 years and how hurricane damage has been extremely detrimental in the elevation and width of beaches. Overlaid terrain profiles, grids displaying change in elevation, and satellite imagery to provide clear insight into how the coastline has dwindled following major hurricanes over the last 20 years.

Smith, P. (2017, May 09). BEACH EROSION: Nature's Work in Progress. Retrieved November 23, 2020, from https://ncseagrant.ncsu.edu/coastwatch/previous-issues/2000-2/early-summer-2000/beach-erosion-natures-work-in-progress/

What You Should Know About Erosion and Oceanfront Development. (n.d.). Retrieved November 23, 2020, from https://deq.nc.gov/about/divisions/coastal-management/coastal-management-oceanfront-shorelines/what-you-should-know-about-erosion-oceanfront-development

The coastline of North Carolina has endured extreme storms leading to severe damage. Fifteen percent of North Carolina’s coastline is critically eroding and eighteen percent of the coastline is severely eroding, this adds up to the coast eroding at a rate greater than 1.4 meters a year. With the strong storms hitting the shoreline directly every hurricane season, the dunes and vegetation is wiped out resulting in an exponential increase in erosion. Our intention through this project is to understand how hurricanes such as Hurricane Sandy, Matthew, and Florence have affected how much sand and beach has been eroded away in these storms over time. We have selected to focus on Oak Island and Bald Head Island to see how the hurricanes hit these islands. We seek to understand how beach replenishment methods have been temporarily effective in building our beaches back up and how the storms still continue to erode away the coast line even with the measures taken to preserve it. We looked at data from before and after the hurricanes and from samples over 20 years before to compare just exactly how much shoreline was lost over these periods of time.

The most prevalent problem in which we recognized throughout this project was the consistent decline in the width of the beaches and shifting of large amounts of sand. These drastic changes on the coastline were direct results of the pounding waves and strong winds from the recurring storms. “Meeting little resistance, Floyd managed to wipe out many remaining dunes, pushing sand across ocean beach roads and into soundside marshes.” In Figures 1 and Figure 2 the decrease in width of the beach is prominent and in Figures 7 it shows the extreme shift in sand. Due to these natural disasters constantly pounding the coast it is essential that the state of North Carolina takes action to protect the businesses and homes in these areas. The risk factor in this area must be considered before any further developments along this coastline.

In order to accurately measure how much natural disasters have affected the coastline of North Carolina, we compiled LIDAR and ICESAT data from NOAA in addition to air photos from USGS of Bald Head Island and Oak Island. From there, we uploaded it to MICRODEM to analyze the differences between all of our data from different time periods. We took data from 1998, 1999, 2005, 2007, 2012, 2014, and 2017 in order to get an accurate depiction of just how much the coastline has changed over time. We examined satellite images to study the buildings along the coast before and after the hurricanes. We also created elevation DEMs from point clouds to study the difference in elevation before and after as well. Additionally, we took a slice from a region to analyze how much the width of the beach has changed over time. We also used a great deal of . Overlaid terrain profiles, grids displaying change in elevation, to see exactly how much the coastline has eroded after these destructive hurricanes during the time period we identified.

In conclusion, it is very apparent that hurricanes in the last 20 years have had a very detrimental effect on the coastline of North Carolina, specifically Bald Head Island. The intense pounding of waves and the strong winds have been the main reason behind the declining beaches along the coast line. As the attraction to coastal houses and businesses grows, it is essential that the beaches keep being replenished and past data is used to predict how future hurricanes can continue to erode the beaches along the coast line. In addition to beach replenishment, dredging along the shoreline would be beneficial in order to slow the sand erosion down. There are no permanent solutions to completely prevent erosion altogether, but with consistent replenishment actions, the beaches can be protected to some degree in order to support the growing populations and attraction to coastal houses and businesses.

Figure 1- 2012 Figure 2- 2007

Figure 3 -2017 Figure 4 - Post Sandy (2014) Figure 6- Difference map Post Sandy (2014) and 2017

Figure 5 - Elevation Profile of Figure 3 and Figure 4. 2017 is shown in blue, 2014 is shown in red.

Figure 7 - 2005 Figure 8 - 1998

For the majority of this project, we used the freeware GIS, Microdem (Guth, 2009). NOAA and USGS provided much of the data and satellite imagery. Additionally, we would like to thank Professor Guth for guiding us through this class and giving us this opportunity to learn and expand our knowledge and abilities.

https://ncseagrant.ncsu.edu/coastwatch/previous-issues/2000-2/early-summer-2000/beach-erosion-natures-work-in-progress/https://ncseagrant.ncsu.edu/coastwatch/previous-issues/2000-2/early-summer-2000/beach-erosion-natures-work-in-progress/