The Mississippi Delta Region: Past, Present, and Future

Abstract

The Mississippi delta region of south Louisiana houses a wealth of resources within a dynamic, subsiding landscape. Foundations for the delta region reflect Neogene evolution of the depocenter, whereas details of the modern landscape reflect late Pleistocene to Holocene evolution of the alluvial-deltaic plain. The Holocene delta plain was constructed by cyclical growth of deltaic headlands, followed by avulsion and relocation of the fluvial sediment source. Abandoned headlands were then submerged and reworked while a new headland was created at the site of active fluvial sediment input. Historic-period levees have decoupled the delta plain from its fluvial sediment source at the same time global sea-level rise was accelerating, which has accelerated delta-plain submergence. Diversions of Mississippi River water and sediment are necessary to achieve delta plain sustainability, but upstream dams trap ∼50% of the total sediment load, and there is not enough supply to keep pace with subsidence and accelerated sea-level rise. The future delta region will not resemble the recent past, and significant drowning is inevitable.