ANTHROPOGENIC EFFECTS TO SAND DUNES ON BARRIER ISLANDS: BRAZOS SANTIAGO PASS AND PORT MANSFIELD PASS, SOUTH PADRE ISLAND, TX

Coastal dunes become well developed with onshore winds, sufficient sediment supply, and plentiful vegetation to assist in stabilization of sand particles (Atkinson et al., 2015). The impacts of large storms periodically change and affect topography and local structures (Pethick, 1984). Dune stability produced by vegetation helps to provide protection of leeward habitats during high storm surges (Tunnell et al, 2002). This study was conducted on Boca Chica Beach and on the beaches South Padre Island, Cameron County, Texas providing 14 topographic transects of sand dunes. The first set of seven of transects began on the most northern end of Boca Chica Beach near the jetties at Brazos Santiago Pass and continuing every kilometer southward for seven kilometers. The second set began near the jetties at the Port Mansfield Pass and continuing every kilometer southward for seven kilometers. Both of these areas are undeveloped areas of the Gulf Coast of Texas.

A comparison of beach-face, berms, storm scalps and sand dune height was taken into account when comparing the data recorded. This study also compared 6 previously recorded profiles from the developed area of South Padre Island, Texas and is focused on the difference of sand dune height between undeveloped and developed locations on this barrier island. The dunes on South Padre Island near Port Mansfield are much larger and are more mature than the dunes on Boca Chica Beach. Overall, the displacements of dune profiles are shown to be rather similar between undeveloped Boca Chica Beach and undeveloped South Padre Island and a highly developed City of South Padre Island. We took into account natural longshore drift, anthropogenic influences for the locations: including and not limited to jetty construction, infrastructure, tourism, vehicular access to beaches, and beach nourishments that somewhat alter the natural profile. It appears that Boca Chica Beach and the undeveloped area of South Padre have healthy beach system with classic dune structures. The City of South Padre Island has attempted to replenish its beach system to a natural state. Although this comparison provides data that shows an ever-changing coastal environment, it is only natural that severe weather, i.e. hurricanes, or seasonal thunderstorms, will drastically change each profile in the future.