Morphodynamic evolution of Bogue Inlet, NC, USA: an annual-to decadal-scale geophysical, hydrodynamic, sedimentological, and microfossil analysis

Abstract

Tidal inlets are the most dynamic and complex sedimentary environments in the coastal zone. The morphologic and hydrodynamic processes acting on the ebb-tidal and flood-tidal deltas aided by the tidal prism allow the transport of sand throughout the complex to drive evolution in correlation with ebb-tidal delta volume. By better understanding these morphodynamic relationships in response to the increase in magnitude and frequency of storms, we can understand the future of coastal siliciclastic systems. This study focused on Bogue Inlet, located on a sediment-starved cuspate embayment, Onslow Bay, on the southeastern coast of North Carolina. The study used a multifaceted approach implementing geospatial, geophysical, sedimentological, micropaleontological, hydrodynamic modeling and a novel stratigraphic model methodology. Geospatial data show that this micro-tidal inlet exhibited migration to the northeast. Furthermore, hydrodynamic and geospatial data suggest the migration pattern is most likely due to the main tidal channel responding to hydraulic changes, forced by back-barrier migration of tidal channels, and the flood tidal delta as the tidal prism changed through time. The hydraulic changes were a function of sediment influx from (natural and unnatural actions), transported by wave and current interactions from varying atmospheric events, with the most extensive morphologic changes observed in the most highly energetic states, hurricanes, and extratropical-like storms. Specific meteorologic events with varying wind direction and magnitude induced the reversal of tidal and longshore currents, leading to a confluence of currents within the inlet, which supported deposition in specific locations on the flood-tidal delta, middle shoals, and ebb-tidal delta. These meteorologic events led to changes in volumetric discharge through the inlet, causing other erosion areas (inlet thalweg). Sedimentological and foraminiferal data show that important parameters of sediment and foraminiferal transport are storm track, size, and magnitude, which can result in the forcing of heightened sea states, causing onshore transport. The digital stratigraphic model and geophysical data moderately agreed on general locations of relict geomorphic features that suggest similar morphodynamic evolution to what is observed in the geospatial data, corroborated by the hydrodynamic data. However, the novel stratigraphic model and the acoustic sub-bottom data were not expected to agree entirely due to one year, five months, and five days between the data used in creating the stratigraphic model and the data collected with the sub-bottom profiler. The geophysical data and stratigraphic modeling also suggest hydrologic conditions that would transport a specific grain size to the deposition locations, creating the features observed in corresponding locations. The results together help constrain the inlet's evolution through time, varying atmospheric conditions, and human influences.