Open AccessAlongshore momentum balances in the nearshore
Author(s) -
Feddersen Falk,
Guza R. T.,
Elgar Steve,
Herbers T. H. C.
Publication year - 1998
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/98jc01270
Subject(s) - wave setup , surf zone , geology , shore , transect , wind stress , forcing (mathematics) , drag , drag coefficient , atmospheric sciences , oceanography , wave propagation , mechanics , physics , mechanical wave , longitudinal wave , quantum mechanics
The one‐dimensional, time‐averaged (over many wave periods) along‐shore momentum balance between forcing by wind and breaking waves and the bottom stress is examined with field observations spanning a wide range of conditions on a barred beach. Near‐bottom horizontal currents were measured for 2 months at 15 locations along a cross‐shore transect extending 750 m from the shoreline to 8‐m water depth. The hourly averaged bottom stress was estimated from observed currents using a quadratic drag law. The wave radiation stress was estimated in 8‐m depth from an array of pressure sensors, and the wind stress was estimated from an anemometer at the seaward end of a nearby pier. The combined wind and wave forcing integrated over the entire cross‐shore transect is balanced by the integrated bottom stress. The wind stress contributes about one third of the forcing over the transect. Analysis of the momentum balances in different cross‐shore regions shows that in the surf zone, wave forcing is much larger than wind forcing and that the bottom drag coefficient is larger in the surf zone than farther seaward, consistent with earlier studies.