Ground-Penetrating Radar Study of North Padre Island, Texas: Implications for Barrier Island Growth and Internal Architecture

Padre Island is the widest and longest barrier island in the world. Padre Island is 190 km long, up to 3 km wide, and ranges from 10-15 meters in thickness. This 2,000 year old barrier island was formed predominantly from northward littorally-drifted sediments from the Rio Grande River Delta.

A 3 km long 50 MHz Ground-penetrating Radar (GPR) profile was collected across Padre Island from the Gulf of Mexico to Laguna Madre, on the northern end of the Padre Island National Seashore. GPR reflectors indicate both seaward and landward dipping clinoforms, as well as concave upward scour and fill reflectors. Seaward dipping reflectors indicate approximately 2 kilometers of seaward progradation of the barrier island, suggesting an average progradation rate of 1 meter/year. Landward dipping reflectors indicate approximately 1 kilometer of landward growth suggesting an average landward growth rate of 0.5 meters/year. Scour and fill reflectors in the central part of the island indicate the presence of 5-9 meter deep tidal and washover channels, suggesting that landward growth was dominantly by short-lived tidal deltas and storm washovers.

Comparison of to the Padre Island GPR data to GPR data collected from an outcrop of a 90 million year old progradational beach/barrier island complex suggests that Padre Island is a modern analog for ancient beach and barrier island systems. In addition, the understanding of the growth history of Padre Island provides much needed information about the evolution of modern barrier island systems.