A three-dimensional surface velocity field for the Mississippi Delta: Implications for coastal restoration and flood potential

Abstract

Accurate estimates of the current rate of subsidence in the Mississippi Delta (southern United States) provide a context for planning of wetland restoration and predictions of storm surge flooding. We present a comprehensive three-dimensional surface velocity field for the Mississippi Delta based on a network of 36 high-precision continuous GPS stations. We show that while the majority of the delta is relatively stable, the southern portion continues to experience high rates of subsidence (5–6 mm yr –1 ). Our data are consistent with long-term tide gauge records at Grand Isle, Louisiana, and several stations in Florida. The current rate of relative sea-level rise (combined effect of land subsidence and sea-level rise) along parts of the coastal delta is ~8–9 mm yr –1 . Most tide gauge stations have recorded sea-level-rise acceleration after A.D. 1970. These data have implications for land reclamation and wetland restoration in the region; parts of the delta may not be viable in the long term.