Storm Impact on Morphological Evolution of a Sandy Inlet

Abstract

Observations of waves, currents, and bathymetric change in shallow water (<10-m depth) both inside and offshore of a migrating inlet with strong (2–3 m/s) tidal currents and complex nearshore bathymetry show over 2.5 m of erosion and accretion resulting from each of two hurricanes (offshore wave heights >8 m). A numerical model (Delft3D, 2DH mode) simulating waves, currents, and morphological change reproduces the observations with the inclusion of hurricane force winds and sediment transport parameters adjusted based on model-data comparisons. For simulations of short hurricanes and longer nor'easters with identical offshore total time-integrated wave energy, but different peak wave energies and storm durations, morphological change is correlated (R2 = 0.60) with storm intensity (total energy of the storm divided by the duration of the storm). Similarly, the erosion observed at the Sand Engine in the Netherlands is correlated with storm intensity. The observations and simulations suggest that the temporal distribution of energy in a storm event, as well as the total energy, impacts subsequent nearshore morphological change. Increased storm intensity enhances sediment transport in bathymetrically complex, mixed wave-and-tidal-current energy environments, as well as at other wave-dominated sandy beaches.