EM 1110-2-1100 (Part V)
31 Jul 2003
Design Constraints
Scientific and Engineering Understanding of Nature
Economics
Environmental
Institutional, Political (Social), Legal
Aesthetics
We also limit the discussion here to the general practice of coastal engineering. Part V-8 is completely
devoted to special, U.S. Federal government planning requirements and design constraints.
(1) Scientific and engineering understanding of nature. The coastal setting is dynamic and influenced
by land, water, and air interactions and processes. It is a regime of extremes, surprises, and constant motion
as the coast responds to changing conditions.
(a) The Coastal Engineering Manual (CEM) demonstrates continued improvement in understanding and
ability to analytically and numerically model nature. For example, Part III-3 discusses analytical methods to
estimate sandy beach shoreline recession rates during storm events that will be useful later in this chapter.
Part III of the CEM also introduces many new, dynamic, numerical models that simulate coastal
hydrodynamics and sediment transport processes.
(b) CP Module. In V-1, the idea of a Coastal Processes Module, (CP Module) was defined as a
repository of physical data and analysis tools relevant to the coastal problem. Wind, waves, currents, water
levels, bathymetry, geomorphology, stratigraphy, sediment characteristics, sediment transport processes, etc.
and the analysis tools (mainly numerical models) make up the CP Module that is employed many times in
the design process (see Figure V-1-1, 2 and 3). However, a fully dynamic, three-dimensional, numerical
model of water levels, waves and sediment transport to simulate bathymetric and shoreline change is still
under development. It remains a long way from routine application for the functional design of coastal
structures. An example would be the simulation of natural, sediment movement behind and through
nearshore breakwaters for both normal conditions and storm events. The inability to accurately predict the
short-and long-term impacts of coastal structures on the nearshore physical environment remains a design
constraint in coastal engineering. Part of the difficulty is the stochastic variability of the natural environment.
(c) Empirical Simulation Technique (EST) methodology. Numerical models are deterministic tools that
produce one solution for each set of boundary conditions. The EST procedure is the numerical, computer
simulation of multiple, life-cycle sequences of systems such as storm events and their corresponding
environmental impacts (Scheffner et al. 1997; 1999). Multiple life-cycle simulations are then used to
compute frequency-of-occurrence relationships, mean value frequencies and standard error estimates of
deviation about the mean. Using the EST procedure for a specific project generates risk-based frequency
information that relates the effectiveness and cost of the project to the level of protection provided.
A user's guide for application of the EST with examples is found in Scheffner et al. (1999). One
example describes calculations of the frequency-of-occurrence relationship for storm-induced,
horizontal recession of beaches and dunes in Brenard County, Florida. Previous references to the
EST procedure are found in Part II-5 and II-8. See also Part V-1 for discussion.
V-3-8
Shore Protection Projects
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