The influence of tidal jet current – Ocean wave interaction on the embayed beach processes Journal Paper
- Author
- Walker, J.H.; Bryan, K.R.; Trembanis, A.C.
- Year
- 2020
- Journal / Source
- Marine Geology
- Volume
- 426
- Number
- 106200
- Summary
- Many embayed beaches are formed by barriers that block embayments to create barrier-enclosed estuaries. These embayed beaches are characterized by strong tidal jets that drain the estuaries through a tidal inlet, often debouching at one end. A field study was conducted on Buffalo Beach in Mercury Bay (Waikato, New Zealand) to study wave energy changes caused by the ebb tidal jet. Acoustic Doppler Current Meter observations showed that during peak ebb jet flow, a decrease in wave height occurred along the beach sites that were in close proximity to the ebb jet. A DELFT3D hydrodynamic and wave model was used to further show that wave height variance was due to the jet current causing shoaling and refraction between the central beach and inlet adjacent southern beach. The resulting wave energy focused along the southern beach, diverged along the central beach and increased the alongshore radiation stress gradient. Under modeled storm conditions within the bay, when wave heights exceed 1.5 m, the jet was found to increase spreading and overall jet width. The jet orientation was also deflected shoreward towards the inlet adjacent headland. The radiation stresses driving alongshore transport became increasingly dominant with increased wave height, suggesting that alongshore sediment mobility increases substantially during a storm event due to the presence of the jet. Implications are that jet strength and orientation play a role in embayed beach rotation.