ERDC/CHL CHETN-I-64
September 2001
Modeling Nearshore Wave
Transformation with STWAVE
by Jane McKee Smith
is to provide guidance for applying the nearshore wave transformation model STWAVE.
Background information is provided to give the context for the application of STWAVE relative
to other wave modeling technology. The STWAVE model is described, and application of
STWAVE within the Surfacewater Modeling System (SMS) interface is discussed. Web sites to
download the STWAVE executable and user manual are given.
BACKGROUND: Wind-wave processes can be separated into three scales: generation,
transformation, and local (Figure 1). Wave generation typically occurs in relatively deep water
and across the continental shelf. The dominant processes for wave generation are atmospheric
(wind) input, nonlinear wave-wave interactions, and dissipation (whitecapping). In intermediate
to shallow water depths, wave transformation processes become dominant. These processes
include wave shoaling, refraction, and breaking. In shallow depths and near coastal structures,
local-scale process of diffraction, reflection, and wave nonlinearities govern. Although there is
overlap in the wave processes between scales, numerical modeling approaches naturally fit into
these three scales.
Figure 1. Scales of wave processes
Generation Scale Modeling: Wave generation occurs over tens, hundreds, and thousands of
miles, as momentum is transferred into the wave field by the winds. Wave heights and periods
increase with wind speed, fetch (distance over which the wind blows), and time, up to fully
developed conditions. Modeling of wave generation and propagation requires accurate wind
field estimation and specification of the basin geometry. For coastal applications, wave
generation modeling is performed at multiple scales, nesting toward the shore. For example, the
Wave Information Studies (WIS) hindcast for the U.S. Atlantic coast includes a 1-deg-resolution
grid of the north Atlantic basin, nesting into a one-fourth-deg grid approximately 1,000 miles
(1,609.34 km) from the coast, which then nests into a one-twelfth-deg grid approximately
300 miles (482.80 km) from the coast. The higher resolution close to the coast provides better
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