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Graduate student seminar - Abby Eckland: Toward understanding, and reversing, delta land area loss

Thursday, March 18, 2021, 2:00PM - 3:00PM


Abby Eckland

River deltas are dynamic and complex landforms that are home to 339 million people worldwide. Rapid deltaic land area loss has been documented since the 1970s (e.g., Mississippi delta), yet few organized plans to reverse land loss exist in the world today. The lack of initiatives to protect and restore deltaic lands is due in part to the remainder of important scientific questions regarding delta processes: what conditions make a delta ecosystem vulnerable?; how do deltas respond to changing sea level and sediment supply?; how do waves and tides impact deltaic sedimentation? To answer these questions, one must evaluate how deltas evolve under various forcing conditions. Prograding deltas evolve through the process of mouth bar aggradation and channel splitting, forming a network of distributary channels and interchannel islands. The number and density of distributary channels in a delta network are wide-ranging and are thought to depend on forcing conditions from the basin, such as wave properties (i.e., height and direction) and tidal amplitude. However, it is unclear how the number, interconnectedness, and density of distributary channels may influence deltaic vulnerability to impacts from climate change, such as coastal flooding from sea level rise and intensified tropical storms. My research will investigate sediment transport processes within distributary networks under a range of boundary conditions to provide insight into the role of distributary networks in stabilizing deltas from sea level rise. I have utilized the 1D water and sediment transport model HydroTrend to quantify the sediment supply at basin outlets (i.e., the delta apex), which is an important boundary condition that controls aggradation and progradation rates. I plan to run Delft 3D, a physics-based numerical model of hydrodynamics, sediment transport, and morphology, to simulate depositional patterns in deltas over short (seasonal to annual) and longer (decadal to centennial) timescales. Comprehensive field studies, which will take place as soon as field work is deemed safe, will enable the collection of detailed hydrodynamic and sediment transport observations and inform model calibration and validation. The Elephant Butte Reservoir delta in New Mexico is a potential field site to study process geomorphology, since reservoir water level fluctuations serve as an analogue for backwater effects or sea level change. Moreover, by applying knowledge from fluvial geomorphology, sedimentology, and hydrology, my research aims to better constrain how deltas evolve via their distributary network systems, and to use these findings to reverse deltaic landscape degradation.