Seminar: John W. Day – LSU, College of the Coast and Environment

UNC-CH’s Department of Marine Sciences is proud to host a seminar by alumnus (1971) John W. Day, Ph.D. This event is scheduled for Wednesday, February 13th, at 3:35pm in room G201 on the ground floor of Murray Hall at the University of North Carolina at Chapel Hill. This seminar will also be broadcast live to both UNC’s Institute of Marine Sciences room 222 and online via Zoom (Meeting ID: 311-406-456).

Presenter Affiliation: Emeritus Professor, Department of Oceanography & Coastal Sciences, Estuary Ecology, Louisiana State University

Title:  Mississippi Delta Restoration and Protection: Shifting Baselines, Diminishing Resilience, and Growing Non-sustainability

Abstract: The Mississippi delta is one of the largest and best studied of global deltas,and like all deltas. The Mississippi rebuilt the modern MRD across the continental shelf of the northern Gulf of Mexico over the past 7 thousand years during a period of relative sea-level stasis. Delta formation was enhanced by a hierarchical series of forcing functions acting over different spatial and temporal scales during a period of stable sea level, predictable inputs from its basin, and as an extremely open system with strong interactions among river, delta plain and the coastal ocean. But within the last century, the MRD has – like many deltas worldwide – also been profoundly altered by humans with respect to hydrology, sediment supply, sea level rise and land use that directly affect sustainability as sea level rise accelerates. Collectively, human actions have tilted the natural balance between land-building and land-loss in the MRD toward a physical collapse and conversion of over 25 percent of the deltaic wetland inventory to open water since the 1930s. The state of Louisiana is investing $50B in a 50-year Coastal Master Plan (CMP) (revised at 5-year intervals) to reduce flood risk for developed areas and restore prioritized deltaic wetlands to a more self-sustaining and healthy condition. It is believed that both hard structures (levees, floodwalls) and wetlands sustained by “soft” projects (river diversions, marsh nourishment, barrier island maintenance) can work together to reduce risk of future hurricane damage to coastal cities, towns and industry, while also protecting livelihoods and ways of life built around harvesting natural resources But the pace of greenhouse gas emissions driving climate change, as well as the inevitable rise in out year energy costs, will make achieving CMP goals ever more challenging and expensive. Regardless of the project portfolios evaluated in the current CMP, the hydrodynamic and ecological modeling underpinning CMP projections indicates that fully implementing the plan will reduce future deltaic land-loss rates by less than 20 percent. Our analysis shows that the cost of delta restoration is quite sensitive to project type and sequencing. Investment is, for example, front-loaded for river diversions and marsh creation but back-loaded for most other project types. Repeated evacuations followed by more or less managed retreat will also continue to be necessary for much of the population even if the existing CMP is improved to increase supply of fine-grained sediments to the MRD. The CMP is ecological engineering on a grand scale, but to be successful it must operate in consonance with complex social processes. This will mean living in a much more open system, accepting natural and social limitations, and utilizing the resources of the river more fully.