Shoreline change at Fort Matanzas National Monument: 2019–2020 data summary

Baron, Lisa

In 2019 and 2020 the Southeast Coast Network collected shoreline data at Fort Matanzas National Monument as a part of the NPS Vital Signs Monitoring Program. Monitoring was conducted following methods developed by the National Park Service Northeast Barrier Coast Network and consisted of mapping the high tide swash line using a global positioning system (GPS) unit in the spring of each year (Psuty et al. 2010). Shoreline change was calculated using the Digital Shoreline Analysis System (DSAS) developed by USGS (Theiler et al. 2008). Key findings from this effort are as follows: A mean of 2,226.56 meters (7,321.7 feet [ft]) of shoreline were mapped from 2019 to 2020 with a mean horizontal precision of 9.90 centimeters (3.9 inches [in]) at Fort Matanzas National Monument during 2019 to 2020. In the annual shoreline change analysis, the mean shoreline distance change from spring 2019 to spring 2020 was -5.70 meters (-18.7 ft) with a standard deviation of 26.25. The shoreline change distance ranged from -48.38 to 119.56 meters (-158.7 to 392.3 ft). Two erosion and one accretion areas were identified in the study area beyond the uncertainty of the data (± 10 meters [32.8 ft]). In the spring 2019 to fall 2019 seasonal shoreline change analysis, the mean shoreline distance change from was -8.79 meters (28.8 ft) with a standard deviation of 22.73. The shoreline change distance ranged from -55.75 to 75.20 meters (-182.9 to 246.7 ft). Four erosion and two accretion areas were identified in the study area beyond the uncertainty of the data (± 10 meters [32.8 ft]). In the fall 2019 to spring 2020 seasonal shoreline change analysis, the mean shoreline distance change from was 3.23 meters (10.6 ft) with a standard deviation of 19.36. The shoreline change distance ranged from -25.82 to 104.93 meters (-84.7 to 344.3 ft). One and four erosion areas were identified in the study area beyond the uncertainty of the data (± 10 meters [32.8 ft]). The annual shoreline change from 2019 to 2020 determined erosion has taken place on the east side of A1A where the Matanzas Inlet is located. Some accretion occurred on the west side of A1A along the Matanzas River, where a spit has formed. The seasonal shoreline change saw that on average, during the spring 2019 to fall 2019 season, almost half the shoreline eroded, with some accretion west of A1A and along the oceanfront beach, southeast of the east parking area. The fall 2019 to spring 2020 seasonal shoreline change analysis determined almost a quarter of the shoreline accreted and the area that eroded during the spring 2019 to fall 2019 season accreted during the fall 2019 to spring 2020 season. Overall, the most dynamic area of shoreline change within Fort Matanzas National Monument appears to be on the east and west side of A1A, along the Matanzas River inlet.

Shoreline change at Fort Matanzas National Monument: 2019–2020 data summary

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