Wave-driven along-channel subtidal flows in a well-mixed ocean inlet

Abstract

Observations of waves, flows, and water levels collected for a month in and near a long, narrow, shallow ($ 3000 m long, 1000 m wide, and 5 m deep), well-mixed ocean inlet are used to evaluate the subtidal (periods > 30 h) along-inlet momentum balance. Maximum tidal flows in the inlet were about 1.5 m/s and offshore significant wave heights ranged from about 0.5 to 2.5 m. The dominant terms in the local (across the km-wide ebb shoal) along-inlet momentum balance are the along-inlet pressure gradient, the bottom stress, and the wave radiation-stress gradient. Estimated nonlinear advective acceleration terms roughly balance in the channel. Onshore radiation-stress gradients owing to breaking waves enhance the flood flows into the inlet, especially during storms.

Radar Remote Sensing Estimates of Waves and Wave Forcing at a Tidal Inlet

“…12b, black curve). These gradients computed using wave parameters derived from the spectral peak are consistent with those computed using the centroidal (energy weighted) frequency and direction (Wargula et al 2014). In particular, both remotely sensed and in situ estimates have onshore (positive) forcing during the high-wave conditions (Fig.…”

“…The spatial wave transformation and hence, the radiation-stress gradients, are affected by refraction and shoaling, and are modulated by dissipation in and around the surfzone (Svendsen 2006). Recent in situ observations of waves and currents at the tidal inlet investigated here (Wargula et al 2014) demonstrated that the breaking-induced gradient of the cross-shore radiation stress contributed significantly to the subtidal alongchannel momentum balance, enhancing the flood flows into the inlet, particularly during storms, similar to results at other inlets (Malhadas et al 2009;Bertin et al 2009;Dodet et al 2013;Orescanin et al 2014).…”

“…Tidal currents were as high as 1.5 m s 21 and were in phase with the 61-m tidal amplitude. Offshore (9-m water depth) significant wave heights [H s , 4 times the standard deviation of sea surface elevation fluctuations in the frequency ( f ) band from 0.05 to 0.30 Hz] ranged from 0.5 to 1.5 m, centroidal (energy weighted) frequencies f c ranged from 0.11 to 0.18 Hz, and waves approached the region from the east-southeast to southeast (Wargula et al 2014). …”

Mobility of meso-scale morphology on a microtidal ebb delta measured using remote sensing

“…Wargula et al, 2014). At the main channel, the flow is also subdivided in two sections, one over the ebb-tidal delta lobe and another directed seaward.…”

Effects of mud supply on large-scale estuary morphology and development over centuries to millennia

“…Different processes caused by waves promote flood dominance (e.g. Bertin et al, 2009;Nahon et al, 2012;Wargula et al, 2014). We expect that the inclusion of more wave processes on sediment transport would lead to faster development towards equilibrium by stimulating flood-directed transport.…”