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Port Isabel High School
http://www.pi-isd.net/

Port Isabel students collect data at three profile locations on South Padre Island: SPI01 in Isla Blanca Park, SPI02 at Beach Access #13 (Moonlight Circle, and the newest site, SPI08, at the Tiki Condominiums (E. Whitesands Street) (Fig. 1). Port Isabel High School has been measuring SPI01 and SPI02 since 1999, and SPI08 since 2007.


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

 

Brazos Santiago Pass, the southern border of South Padre Island, is dredged biannually. The pass serves as the southern Gulf of Mexico access to the Gulf Intracoastal Waterway and the Port of Brownsville. Dredged material is placed on beaches of South Padre Island, and the three sites monitored by Port Isabel High School students are within the nourishment areas. The SPI02 monitoring site has also been used by students and scientists to monitor the growth of dunes. When SPI02 was established in August 2000, there were no dunes between the seawall and the waterline at this location. Since that time, sand fences have been installed, and vegetation has been planted. Profile data have been quantifying the effects of these actions (Fig. 2). Whereas the vegetation line has remained in a similar position throughout the study period, beach volume at this location has been increasing owing to a slowly accreting shoreline and entrapment of sand in the dune area. Hurricane Dolly made landfall on South Padre Island near Port Mansfield on July 23, 2008. Impacts to beaches and dunes in the Port Isabel students' study area were not measured because of the arrival of Hurricane Ike before their first field trip. The storm surge due to Hurricane Ike deposited sand in the dune area at SPI02 and covered the vegetation, essentially flattening the profile. Although shoreline position and beach volume appear steady at this site, the vegetation line moved seaward during the 2012–2013 academic year. A large push-up dune, seaward of the vegetation line, has been created by beach maintenance practices (beach scraping to remove seaweed). This accounts for the increase in beach volume at SPI02 (fig. 2) and the change in the beach profile shape. If there are no major storms to cause dune erosion, vegetation should begin to grow on the push-up dune.

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Figure 2. Changes at SPI02 on South Padre Island due to beach-nourishment projects, the installation of sand fences, and beach maintenance practices.


Starting in the 2007–2008 academic year, students at Port Isabel High School began gathering data at an additional monitoring site at a chronically eroding location in front of the Tiki Condominiums near the north end of the city, SPI08. This site has a narrow beach backed by a seawall that periodically receives nourishment sand from road maintenance north of the City of South Padre Island. During the May 14, 2010, field trip, Port Isabel students and UT scientists observed that sand fencing had been installed and vegetation planted adjacent to the seawall. When the students returned to the site on September 28, 2010, the sand fence had been removed, and there was no trace of vegetation in front of the seawall. The narrow beach at this site appeared to be unable to support dune formation.

A larger beach-nourishment project using sand dredged from Brazos Santiago Pass was completed on South Padre Island in early 2011. The width of the beach and volume of sand significantly increased at the SPI08 location, although there are still no dunes or vegetation in front of the seawall (Fig. 3). On the May 13, 2011, field trip, students observed that a 0.5-m scarp had formed at the shoreline. Port Isabel students continued to monitor this site during the 2011–2012 academic year to determine whether the nourished beach would reach equilibrium. The shoreline position has returned to the prenourishment position. After an initial, significant decrease in beach volume (to prenourishment levels), volume on the backbeach has increased steadily owing to installation of sand fences. As of May 2013, the sand fences remained in place, serving to trap sand in front of the seawall at this site, and vegetation has been planted on the incipient dunes. On the final field trip of the 2013–2014 academic year a large push-up dune was present seaward of the vegetation line. Port Isabel students will continue to monitor this rapidly changing and chronically eroding location.

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Figure 3. Volume and shoreline changes at SPI08 on South Padre Island due to beach-nourishment projects, the installation of sand fences, and beach maintenance practices.


BEG Texas Coastal Management Program NOAA