UPPER TEXAS COAST UNPRECEDENTED EROSION: INTENSE HURRICANE IMPACTS AND ACCELERATED SEA-LEVEL RISE RESPONSE

Current rates of barrier migration along the upper Texas coast are unsustainable given the age of the barriers. By quantifying long-term sand accumulation offshore and in San Luis Pass Tidal Delta, we can compare long-term and short-term erosion of Galveston Island. Currently, the only source of sand into these locations is erosion of Galveston Island itself. The average hurricane-related offshore sand flux from ~5,142 yr B.P. to present was ~4,306 ± 673 m³/yr, with a decrease in this sand flux from ~2,692 yr B.P. -present to ~931 ± 271 m³/yr. San Luis Pass Tidal delta formed ~2,100 yr B.P., when the rate of sea-level rise began to decelerate from ~2.0 mm/yr to ~0.6 mm/yr. We quantify additional sand eroded from Galveston Island between ~2,100-200 yr B.P. to be ~4,700 m³/yr based on deposition into San Luis Pass Tidal Delta. Compared to modern rates of change, this erosion appears to have increased to ~10,000 m³/yr over the past ~200 years based on historic navigational charts and sediment cores. A summation of these volumetric fluxes together with published sand fluxes to the Galveston Island shoreface environment equals a total of ~130,361 ± 28,271 m³/yr. This value is considerably lower than the ~215,000 ± 48,000 m³/yr that would have been produced from an equilibrium profile shift associated with the measured historic erosion rates. This unprecedented erosion is associated with the recent accelerated sea-level rise and coupled constant hurricane impacts, with only a minor signal from anthropogenic influences.