EM 1110-2-1100 (Part II)
30 Apr 02
a combination of general understanding of coastal behavior and insight into the design needs of the specific
project. Some processes are almost always a concern for certain project types. For example, circulation and
flushing are generally evaluated in a harbor project.
c. Interaction between processes. It is important to remember that although meteorological and
hydrodynamic processes are often discussed individually, they impact a project in combination. This
combination of processes leads to two strong implications for design:
(1) Processes mutually interact and cannot always be treated as being independent of each other. For
example, water level affects waves by influencing shallow-water transformation and breaking.
(2) Extreme occurrences of one process often coincide with strong or extreme occurrences of some other
processes. For example, strong winds, large waves, and elevated water levels often occur together during a
severe storm.
II-8-3. Acquiring Information
a . Identifying available information. The available meteorological and hydrodynamic information for
coastal design is rarely adequate for direct use. Typically all reasonable information sources on relevant
processes are identified. Then the information is modified and carefully interpreted in various ways to arrive
at the required design conditions. Part II-8 provides a guide to available sources of wind, wave, water level,
and current information.
b. Consideration of collecting field measurements. Field measurements can be very helpful at a project
site, especially if the information already available is seriously limited in quality and representativeness.
Often the needs and scope of coastal projects justify some level of field study. Field measurements must be
carefully planned so that the project schedule can accommodate the time and cost required for collecting and
analyzing data. Measuring any extreme storm events during the life of a project level study is a matter of
chance, but at least some routine storm events are typically recorded. Field measurement options are
discussed in Part VII-3. Field measurements have the following potential advantages:
(1) Direct documentation of processes at the project site.
(2) On-site data can be correlated with a better documented, related location (such as a point for which
long-term measurements or hindcasts are available).
(3) Onsite data for calibration and validation in model studies.
c. Numerical and physical modeling possibilities. Numerical and physical models offer powerful tools
to assist in design analysis. They are used for evaluating existing conditions at a site and various alternative
modifications. Both modeling tools are discussed in Part VII. In terms of meteorology and hydrodynamics,
numerical models are typically used for:
(1) Extending the length of record.
(2) Hindcasting extreme events not included in the available information.
(3) Synthesizing hypothetical, but possible, extreme events (such as historical hurricanes with modified
tracks).
(4) Transferring information from a related, better documented location to the project site.
II-8-2
Hydrodynamic Analysis and Design Conditions
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