Speakers

Alexander S. Kolker, PhD

Dr. Kolker is an Associate Professor at the Louisiana Universities Marine Consortium. He studies climate change, sea level rise, resilience, and change in coastal systems. He has worked in systems across the world, including the Mississippi River Delta, Florida Everglades, the Atlantic Seaboard of the US, and North Africa. His research has spanned across the coastal zone, investigating topics as diverse as the response of coastal wetlands to climate change, the distribution of air pollutants and greenhouse gases in industrialized zones, the controls on subsidence in deltaic environments, the geological implications of carbon capture and sequestration, and the geomorphology of deltaic environments.

As a scientist who works in a region surrounded by climate impacts, Dr. Kolker is deeply interested in how coastal change impacts coastal residents. He has served on numerous panels, including the Science Advisory Group for Louisiana's Governor's Climate Initiative Task Force (which seeks to reduce Louisiana's emissions to net-zero by 2050), the Framework Development Team for Louisiana's 2017 Coastal Master Plan (which seeks to build land and reduce flood risk in Louisiana's coastal zone), and a National Academy of Sciences committee on the Gulf of Mexico.

Dr. Kolker received his Bachelors' degree from the University of California, Santa Cruz and his Master’s and Doctoral degrees from Stony Brook University. During the 2019-2020 academic year, Dr. Kolker was a Fulbright Scholar in Morocco, and he presently serves on the Fulbright Specialist Roster. He currently lives in New Orleans, LA.

Presentation Description

This talk describes the evolution of Neptune Pass, the largest single distributary to emerge in the Mississippi River in over 50 years. The system developed in 2019 and 2020, as a small channel enlarged and deepened- increasing flow by at least order of magnitude. Causative factors include the degradation of aging infrastructure, the impact of ~15 years of high river conditions, hurricane strikes, and a possible backstepping of the mouth of the Mississippi River due to subsidence and sea level rise. In 2022, the system carried ~ 15% of the flow of the Mississippi River, ~ 118,000 ft3 s-1, when the lower river flowed at ~ ⅔ of its maximum discharge (775,000 ft3 s-1), rivaling the river's largest distributaries. Furthermore, Neptune Pass is in a reach of the river where about 1/3 of the total flow of the river was flowing eastward, raising concerns for river management that led to bank stabilization efforts.

A vigorous field campaign, jointly supported by CPRA’s Lowermost Mississippi River Management Program and the National Wildlife Federation, was initiated to understand Neptune Pass, its formation, current conditions, potential for future development. Marine geophysical surveys, including bathymetric surveys and discharge measurements were conducted to understand the evolution of the channel and subsurface features. Drone-based LIDAR surveys, coupled with satellite image analysis were used to quantify subaerial lands and predict future development. As of the end of 2022, results show the development of 1000 - 2000 acres (4-8 km2) of mouth bars and other shallow-subtidal features. A preliminary sediment budget indicates that volume of newly deposited lands exceeds the volume of scour in Neptune Pass channel by about 1/3 suggesting that deltaic landforms are evolving. Management discussions regarding the long-term status of Neptune Pass are ongoing and will be discussed in the context of these results and continued monitoring of this system.

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