Investigating Shallow, Coastal Morphodynamics Using X-Band Radar: Discerning Sediment Transport Pathways Through Tidal Inlets

Jesse E. McNinch, Ph.D.

U.S. Army Corps of Engineers
Field Research Facility

Tuesday, Mar. 7, 2017, 10:00am
Chase 130

The persistence of large-scale, nearshore morphologic features, such as ebb tidal deltas fronting tidal inlets, are difficult to reconcile on beaches with large, wave-driven alongshore transport volumes without assuming that: 1) hydrodynamic processes creating these features are sustained through a variety of oceanographic conditions(i.e. a balance of waves and currents), and 2) a quasi-equilibrium of sediment transport processes shaping these features is maintained while enabling a large volume of sediment to be transported through. One would otherwise expect tidal inlets to either close or have a near-total seaward bypassing of sediment around the inlet mouth. These examples do exist in nature but are rare and, more commonly, tidal inlets maintain seaward and landward deltas and allow an exchange of sediment between adjacent islands. Understanding these processes, and particularly the mode of sediment transport in which they occur is important to accurately model alongshore and 3-dimensional beach morphology, as well as tidal inlet morphodynamics. Part of the challenge is the paucity of observational data and the difficulty in measuring bathymetry over these features at high temporal and spatial resolutions, especially during storm events. Results from the Radar Inlet Observing System (RIOS), deployed at Oregon Inlet, North Carolina from July 2016 to present, will be discussed. RIOS utilizes hourly X-band radar data (1Hz, 10-min duration) to define shoal position and morphology from measured wave breaking and wave speed. Three sediment transport pathways, reflecting different mechanisms of transport, are evident at Oregon Inlet. Preliminary results suggest sediment transport modeling must include astronomical and wind-driven currents, waves and breaking-wave currents, and seaward- and landward-migrating bedforms over a range of spatial and temporal scales. Implications to dredging strategies continue to be explored.


Jesse E. McNinch received his Ph.D. in Geological Oceanography from the University of North Carolina-Chapel Hill in 1997 where he investigated sedimentary and physical processes responsible for the development of the Carolina Capes. He then served the Field Research Facility as a Postdoctoral Research Associate with the National Academy of Sciences NRC program studying the influence of geology on beach erosion around the Outer Banks of North Carolina. He was tenured in 2006 as an Associate Professor in the Department of Physical Sciences at the Virginia Institute of Marine Science, College of William and Mary and developed a research program centered on shoreline and shelf morphodynamics. Jesse returned to the Field Research Facility in 2008 and continues his work in coastal morphodynamics, through an approach that couples geology and hydrodynamics. McNinch is an experienced SCUBA diver, USCG licensed captain, avid sailor, and lifelong fan of maritime history and cartography.