Wind, Wave, and Engineering Effects on Tidal Inlet Morphodynamics

Joshua L. Humberston
Doctoral Dissertation Defense


Tuesday, May. 4, 2021, 1:00pm
Chase 105

This body of work examines the hydro- and morpho-dynamics of tidal inlets using a diverse array of research tools. A custom X-band radar system (RIOS) is designed and used to track the evolution of shoal features over the ebb-tidal delta at Oregon Inlet, NC. Analysis of the data reveals that alongshore shoal migration rates are closely correlated to wave-driven alongshore sediment transport, and also that the cross-shore bedform migration rates are tightly correlated with a sub-tidal water level gradient through the inlet. A follow-up experiment with in-situ sensors suggests that the sub-tidal gradient is set up by regional winds and that the resulting pressure gradient significantly alters the tidal inlet hydrodynamics, at times entirely reversing tidal flows. Finally, the geomorphic impact of wind-driven currents, as well as waves and the insertion of a terminal groin, is tested through an idealized numerical modeling study of a synthetic inlet system. The addition of a sub-tidal water level gradient has substantial and cascading effects on the inlet system morphology, potentially suggesting that the traditional inlet classification system, based only on the wave and tidal properties, should be modified to include wind influence.


Josh Humbsterson completed his B.S. in geology with a concentration in coastal and marine geosciences at the University of Delaware. Through an NSF-funded Research Experience for Undergraduates (REU) and his senior thesis research project, he used naturally occurring radionuclides that adsorb to fine grain sediment to predict seasonal deposition patterns in the Delaware Estuary. He then completed an M.S. in oceanography at UNH through CCOM/JHC where his research focused on predicting surficial mud fraction in the Little Bay estuary using a statistical decomposition of single-beam sonar data. Following that, Josh spent some time on the NOAA Ship Okeanos Explorer as a hydrographer then completed a year of Ph.D. work at Coastal Carolina University in Conway, South Carolina where he worked analyzing radar observations of surface waves. Josh spent a summer working with the US Army Corps of Engineers at their Coastal and Hydraulics field facility in Duck, NC through the PATHWAYS program. Josh then received a SMART scholarship through the Department of Defense (DoD) and has returned to UNH to complete his Ph.D. in oceanography. His research takes an interdisciplinary approach to better explain shore-oblique sandbars: how and where form and how they evolve. He will also explore tidal inlet ebb-shoals evolution and the varying sediment pathways hosted in these systems. Josh's research interests include coastal morphodynamics (sandbar and shoal evolution), coastal influence of ocean surface waves, coastal geologic influences, estuarine sediment dynamics, and remote sensing (acoustic and X-band radar).