A longshore current model which includes a modification of the bottom
stress term due to the effects of breaking-wave induced turbulence is
developed and applied to field data from both barred and planar beache
s. This turbulence is postulated as producing a vertical mixing which
alters the near-bottom vertical profile of the longshore current. As a
result, the bottom fiction coefficient, c(f), used to relate the free
stream current velocity to the bottom stress is modeled as consisting
of two components, c(fl), a spatially constant value which is assumed
to be related to bottom characteristics and c(fr), which is dependent
upon breaking-wave induced near-bottom turbulence levels. Employing a
one-dimensional turbulent kinetic energy equation to model this break
ing-wave induced turbulence, a spatially varying bottom friction coeff
icient is obtained. The spatially constant c(fl) is estimated based on
data taken seaward of the surf zone, where the wind stress is assumed
to be balanced by the bottom stress. The concept is demonstrated with
out the inclusion of horizontal mixing in the longshore current model
formulation. The model predicted cross-shore profiles of longshore cur
rent show improved agreement with observations compared with treatment
s using constant c(f) values.