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Recent Reductions of Subsidence Rates in the Mississippi River Delta Plain

Recent Reductions of Subsidence Rates in the Mississippi River Delta Plain. Julie C. Bernier 1 and Robert A. Morton 2 1 U.S. Geological Survey, Florida Integrated Science Center, St. Petersburg, FL 2 U.S. Geological Survey, Florida Integrated Science Center, Austin, TX.

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Recent Reductions of Subsidence Rates in the Mississippi River Delta Plain

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  1. Recent Reductions of Subsidence Rates in the Mississippi River Delta Plain Julie C. Bernier1 and Robert A. Morton2 1U.S. Geological Survey, Florida Integrated Science Center, St. Petersburg, FL 2U.S. Geological Survey, Florida Integrated Science Center, Austin, TX

  2. Introduction – Historic Wetland Loss • Delta plain: ~ 4000 km2 land loss since 1930s

  3. Objective • Identify historic trends and most recent subsidence rates through integration of: • tide-gauge records (NOS) → relative sea-level rise (RSLR) • repeat leveling surveys (NGS) → decadal elevation change • continuous GPS (CORS) → short-term elevation change

  4. Integrated Datasets

  5. Grand Isle Tide Gauge • Mid-1960s to early 1990s: accelerated RSLR

  6. Bayou Lafourche Leveling Line • 1982-1993: accelerated subsidence

  7. Integrated Datasets: Temporal Trends 2003-2007: -4.4 mm/yr 1961-1984: -13.6 to -18.7 mm/yr 1965-1993: -9.6 mm/yr 2002-2007: -3.5 mm/yr 1966-1993: -11 mm/yr 1947-1965: -3.3 mm/yr 1965-1993: -10.7 mm/yr 1993-2006: -4.1 mm/yr 2003-2007: -6.3 mm/yr

  8. Delta-Plain Subsidence Rates

  9. Subsidence Mechanisms

  10. Delta-Plain Oil-and-Gas Fields

  11. Bayou Lafourche Leveling Line • Highest rates occur over nearby producing fields

  12. Conclusions and Implications • Decadal-scale acceleration and subsequent deceleration of historic subsidence rates was likely induced by deep subsurface hydrocarbon production • Most recent subsidence rates are comparable to rates averaged over geological time scales • A better understanding of most recent trends and processes causing subsidence needs to be incorporated into coastal restoration efforts and efforts to model expected impacts of increased RSLR

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