THSCMP - Port Aransas High School

Beach and Dune Monitoring on Mustang Island
Tiffany Caudle and Jeffrey Paine

Port Aransas students collect data at three profile locations on Mustang Island: MUI01 near Horace Caldwell Pier, MUI02 in Mustang Island State Park, and MUI03 (Fig. 1). Port Aransas High School has been measuring these profiles since 1999.

figure 1

Figure 1. Location map of Port Aransas High School monitoring sites.

The beach-monitoring activities of Port Aransas High School students have also provided beneficial information regarding the beach and dune system on Mustang Island. The dune system on Mustang is healthy, with tall (>3 m), wide foredunes along most of the island. The only breaks in the foredune system are at beach-access points and washover features. On Mustang Island, beaches are regularly scraped to remove seaweed from the forebeach. The sand and seaweed removed from the berm and forebeach are regularly placed at the seaward base of the foredunes. Since the beginning of the coastal monitoring program, Port Aransas students have been monitoring the growth of the foredune system at their profiling sites. Figure 2 is an example of expansion of the foredune at MUI01 near Horace Caldwell Pier in Port Aransas. Note that the width of the dune increased between 2001 and early 2012, although the shoreline remained in a relatively stable position.

Figure 2

Figure 2. Foredune expansion at MUI01 on Mustang Island.

In October 2012, a large part of the dune face had been excavated (Fig. 3) for a beach-maintenance practice called dune notching. Students documented that sand was replaced in the foredune by May 2013 and that the vegetation line has been re-established at the toe of the dune. The dune had again been notched during the 2014–2015 academic year. The excavated area was slowly being filled in between 2016 and 2018. During the field trips of the 2017‒18 academic year the foredune had been completely refilled (Fig. 4). By the end of the 2018‒19 academic year the foredune was revegetated and stabilized. The current width of the foredune is still narrower and the volume of sand in the profile is less than when THSCMP began monitoring in 1999. Also, the crest of the foredune is lower in elevation because the dune crest was not stabilized by vegetation for a period of time and sand was carried away by the wind. Beach maintenance practices such as beach-grading and dune-notching will continue to be monitored by Port Aransas students at MUI01 and compared with the natural processes that occur at MUI02 in Mustang Island State Park.

Dune Excavation

Figure 3. Excavated dune profile and photos at MUI01 on Mustang Island.

Figure 4

Figure 4: The dune notch at MUI01 in 2015 and same location filled and vegetated in 2019. Note the beach and dune volume has not recovered to the pre-dune notching values (practice began in 2012).