uses minimal data input to provide qualitative results under simplified conditions, appropriate for a
reconnaissance-level study or to identify possible project alternatives. The design mode is a rigorous
application of the model in which all available data and knowledge about the project site are applied
for model setup, calibration, and verification; evaluation of project alternatives; and design optimiza-
tion. Data requirements are different for these two modes of application. As with any type of model
application, the degree to which SBEACH predicts prototype profile evolution is dependent on the
quality of the input data set, and level of application. Engineering judgement is required in interpret-
ing model predictions.
Scoping mode. In the simplest application, SBEACH may be run with only one setup file, called the
configuration file. Model calculation parameters may be set to default values, and constant wave
height, period, angle, water elevation, wind speed and direction may be specified. A measured pro-
file is not required, and the input beach profile can be defined schematically through the configuration
file. Project alternatives, such as the addition of beach fill and/or a seawall, may easily be evaluated.
If desired, any one or more of these input data types may be changed, and designated in additional
input files to increase the detail of the scoping mode application.
Design mode. For detailed evaluation and optimization of project alternatives, SBEACH is ideally
calibrated and verified prior to application. Calibration refers to the procedure of adjusting SBEACH
calculation parameters such that the model reproduces the change in profile shape produced by an
actual storm. Verification involves applying the calibrated model to reproduce profile change on the
same beach for another storm, or to reproduce profile changes for the same storm but at different
locations within the project area, using profiles with different cross-sectional shapes. For calibration
and verification, representative profile data prior to and immediately following a storm event with
known wave and water level conditions, as well as the beach characteristics, are required. Reproduc-
tion of profile change on the subaerial part of the beach, particularly the dune and berm, are usually
emphasized for engineering purposes. Once the model is verified, design storm events may be run
with the existing profile and various design alternatives to determine impacts and advantages of each.
In practice, ideal calibration and verification data are not always available. For these cases, calcula-
tion parameters used for a project with similar beach and storm characteristics may be adopted, model
sensitivity to a range of calculation parameters may be assessed, and/or the default calibration param-
eters may be used. Predicted results should always be compared with available knowledge of site re-
sponse to lend credibility.
MODEL OUTPUT: SBEACH produces four types of output data: simulated profiles (at intermedi-
ate time steps (if specified) and the final calculated profile); the cross-shore variation of several physi-
cal parameters (intermediate (if specified) and maximum wave height, intermediate (if specified) and
maximum total water elevation and setup, maximum water depth, and volume change); a record of
the various beach response and coastal processes that occurred during the simulation (accretion, ero-
sion, overwash, boundary-limited runup, and/or inundation); and a report that reiterates input data as
well as output parameters of interest. Parameters usually of interest in application of the model in-
clude maximum recession distances at user-specified elevation contours (up to three), and the land-
ward-most occurrence of a user-specified erosion depth. Thus, the impacts of project alternatives on
beach response (erosion, accretion, bar/trough formation, recession, etc.), wave height, water level,
volume change, and the dune and/or upper beach (e.g., inundation, overwash) may be investigated
with SBEACH.
CETN 9 / 9 4
Previous Page
