APPLICATION OF GEOPHYSICAL TECHNIQUES TO STUDY THE INTERNAL ARCHITECTURE OF COASTAL DUNE MORPHOLOGY, NORTH PADRE ISLAND, TEXAS

The Texas coast contains the longest barrier island, Padre Island. Large populations visit the beaches in this area disturbing the natural environments and affecting the ability of the foreshore and dune environments to protect the mainland from erosional events. Sand dunes provide protection from these events due to their location on the highest point of the barrier islands. Dunes absorb the impact of storms, and prevent floods from damaging coastal cities. Coastal dunes in the northern portion of North Padre Island gain sediment through longshore drift from the northeast. In order to help with the erosion, maintained dunes are being constructed and sustained with planting of vegetation on the seaward side along the Gulf Coast. Differences in the internal structure of naturally formed dunes and maintained dunes can provide crucial information on the effectiveness of maintained dunes. The study of coastal dunes on North Padre Island, Texas, provides insight to the benefits of protecting dunes through management programs, as well as effectiveness of maintenance on these dunes. This study utilizes GSSI Ground Penetrating Radar with frequencies of 200 and 400 MHz to study the shallow subsurface characteristics. Penetration ranges from 0 to 4 m and 0 to 2 m, respectively, for these two systems. Vertical resolution is approximately 0.14 m and 0.07 m. Six profiles were collected on two dunes, three perpendicular and three parallel to shore. In the radar profiles, truncated reflectors indicate a potential erosional event. Two erosional events are identified in the natural dune, and one erosional event is seen in the maintained dune. Future work includes laser particle size analysis to identify possible correlations between grain size trends and erosional events found in the radar data.