Effects of Locally Generated Wind Waves on the Momentum Budget and Subtidal Exchange in a Coastal Plain Estuary

Abstract

A numerical model with a vortex force formalism is used to study the role of wind waves in the momentum budget and subtidal exchange of a shallow coastal plain estuary, Delaware Bay. Wave height and age in the bay have a spatial distribution that is controlled by bathymetry and fetch, with implications for the surface drag coefficient in young, underdeveloped seas. Inclusion of waves in the model leads to increases in the surface drag coefficient by up to 30% with respect to parameterizations in which surface drag is only a function of wind speed, in agreement with recent observations of air‐sea fluxes in estuaries. The model was modified to prevent whitecapping wave dissipation from generating breaking forces since that contribution is integrally equivalent to the wind stress. The proposed adjustment is consistent with previous studies of wave‐induced nearshore currents and with additional parameterizations for breaking forces in the model. The mean momentum balance during a simulated wind event was mainly between the pressure gradient force and surface stress, with negligible contributions by vortex, wave breaking (i.e., depth‐induced), and Stokes‐Coriolis forces. Modeled scenarios with realistic Delaware bathymetry suggest that the subtidal bay‐ocean exchange at storm time scales is sensitive to wave‐induced surface drag coefficient, wind direction, and mass transport due to the Stokes drift. Results herein are applicable to shallow coastal systems where the typical wave field is young (i.e., wind seas) and modulated by bathymetry.

A New 1D/2D Coupled Modeling Approach for a Riverine‐Estuarine System Under Storm Events: Application to Delaware River Basin

“…The study area here is Delaware Bay, which is one of the largest and most important bays along the U.S. East Coast. It is also a generalizable example of shallow coastal estuaries (Pareja-Roman et al, 2019). The hydrodynamic characteristics in the Delaware Bay are determined by the interaction of the tidal flow from the Atlantic Ocean and the freshwater flows from the mainstem of the Delaware River and its tributaries (Dupont, 2019).…”

Estuarine retention of larvae: Contrasting effects of behavioral responses to turbulence and waves

“…Time‐averaged velocities in the channel are into the bay at depth and out of the bay at the surface (e.g., Geyer and MacCready 2014), though time‐averaged velocities on the flats can often be out of the bay at all depths. Significant wave heights are typically less than 0.2 m, but because Delaware Bay has a large fetch, strong winds can occasionally (< 10% of the time) generate waves with significant wave heights up to 2 m (Chen et al 2018; Pareja‐Roman et al 2019).…”

Modeling of water waves and sediment transport using physics-based and machine learning methods

“…During the past several decades, considerable progress has been made in physics-based wave models based on wave action and momentum balance principles. Different wave models can be employed to simulate spatial and temporal characteristics of waves in shallow bays (e.g., Pareja-Roman et al, 2019;Chen et al, 2018;Mariotti et al, 2010;Salatin et al, 2021). For example, Kukulka et al (2017) combined the Regional Ocean Modeling System (ROMS, Shchepetkin and McWilliams, 2005) and the spectral model of Simulating Waves Nearshore (SWAN, Booij et al, 1999) to investigate surface wave dynamics in Delaware Bay.…”