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THE WORKSHOPS
Eugene H. Harlow and John B. Herbich
The purpose of this meeting was to gain a clearer picture of the
principal factors affecting the design of entrances to ports and
harbors, and their interaction. To further this purpose, the workshops
were structured by the panel to elicit as much of the experience,
training, and informed opinion represented by the assembled
participants as possible in identifying outstanding problems requiring
solution. From a full list of these problems, the consensus of the
group would be sought on the ten most important, and their order of
significance or urgency.
Nominal Groups
The structure selected by the panel for the workshops was that of
nominal groups. In nominal groups, the members work in one
anotber's presence, but without interaction. It teas been demonstrated
that in the critical phase of program planning reserved for speculative
consideration of all aspects of a problem, or of the range of
alternative directions and objectives a program might follow,
interacting groups tend to generate and pursue far fewer ideas than
nominal groups. 2 The nominal group technique allows a period for the
silent generation of ideas. Each member then presents an idea in turn,
continuing until all ideas are recorded or the alloted time expires.
The ideas are not discussed: questions may be asked for clarification
of statements.
First Workshop
Participants were divided by expertise and interest into three
nominal groups to develop statements of the problems faced in the
design of entrances to ports and harbors in the areas of: nature and
the environment, the concerns of ship owners and operators, and design
and maintenance. Their statements were recorded and numbered on large
sheets that were then brought to plenary session. (These statements
are listed in Appendix A.)
157
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Second Workshop
The participants were assembled to read all the statements, and
each was asked to list bis ten selections, in order of the ten most
important problems. To avoid spreading the votes too thinly,
essentially similar statements were combined for a single vote. (These
omnibus statements are also listed in Appendix A.) The votes were
tallied, and the statements were announced. Owing to a tie vote,
eleven statements were selected.
Each statement was given to a small working group for a title,
final articulation, and the statement of preliminary objectives for
research and other actions addressing the problems identified. These
were reviewed and refined by the assembled participants, and the
meeting adjourned. The product of the workshops is given in the
succeeding section.
The Most Urgent Problems in the Design of Entrances
to Ports and Harbors
1. PREDICTION OF SHIP MOTIONS
Improved and validated models are needed for the prediction of ship
motions, vertical and horizontal, in the environmental and operational
situations found in harbor entrances. These models are needed in the
development of channel design geometry (depth, cross-section, shape,
and planform), in the assessment of operating limits and traffic
capacity, and to support the training of operators (simulators).
Specific areas of weakness in existing models that should be addressed
by research programs are:
--Lack of data on a wide range of ship types;
--Inability to predict the effects of
Restricted water conditions {shallow water, banks),
Complex, three-dimensional currents,
Waves on lateral and vertical motions in restricted
waters,
Passing ships,
Tugs and other auxiliary devices;
--Scale effects associated with physical models.
Research Objectives
Addressing the weaknesses of existing models, as listed above in
approximately their order of importance, constitutes a preliminary
re~earob program. In all cases, research efforts abould be directed by
a balanced program of:
--Physical model testing, both captive and free-
running, to develop data bases;
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159
--Development of analytical predictions; and
--Selected full-scale tests for validation or
data generation, or both.
2. USE OF SYSTEMS - =YSIS IN To DESIGN OF FOR ENTICES
The design, construction, and operation of harbor entrances involve
the interaction of various government and non-government entities--ship
operators and owners, the U. S. Army Corps of Engineers, the U. S.
Coast Guard, National Ocean Survey (of the National Oceanic and
Atmospheric Administration), Environmental Protection Agency, local
port authorities, pilots and other state interests, local populace and
governments--and interactions with other modes of transport,
recreational boating, shoreside industries, and national and local
economic interests. These interests are not all given adequate
consideration in an integrated or systems-analytic manner in the design
of harbor entrances.
Research Objectives
--Develop a detailed systems analysis procedure for use in
harbor-entrance design
--Test the design procedure for one or more sample
ports, and modify as necessary
--Sponsor interdisciplinary seminars to disseminate
the systems-analysis approach, and to discuss major
technical issues.
3. ENVIRONMENTAL DATA
There is a need for reliable, economical measurement, reduction,
presentation, and storage of environmental data, including: tides,
currents, waves, sediments, bathymetry, geometry, salinity, wind", fog,
ice, and water samples (chemical analysis).
Research Objectives
The research program conducted to address these needs should
determine what improvements are needed in:
--Accuracy,
--Automatic analysis techniques,
--Storage and retrieval techniques and procedures,
--Display, and
--Instrumentation
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to meet the requirements of users. Some of the basic questions that
will arise in the course of answering needs for environmental data are:
--Length of measurement for a single run,
--Interval between runs,
--Spacing, and
--Distinguishing interactions.
4. MODELS OF THE p~rsIcAL ENVIRONMENT
Cost-effective model. for predicting the environmental conditions
affecting harbor-entrance design need to be evaluated, improved, and
validated. These should provide typical and extreme values of waves,
currents, winds, water levels, salinity, sedimentation, water quality,
and other environmental parameters as a result of both natural
conditions and changes caused by human activity. The information to be
provided is critical to the rational design of safe and efficient
harbor entrances; for example, the basic forcing functions for
ship-motion modeling, determination of maintenance dredging
requirements, and ability to evaluate alternative designs and assess
environmental effects.
Researab Obi ectives
The general needs to be addressed are tbose leading to improvements
in the test data, numerical techniques, "caring techniques, physical
processes, and forcing functions for each parameter and the
interactions between parameters. Some examples of specific problems
are:
--Cost effective two- and three-dimensional
matbematical models of all hydrodynamic processes,
--Mbvable-bed modeling, "caring, and operational
procedures,
--Dispersive transport scaling in physical models,
--Two- and three-dimensional models of transport,
deposition and erosion of cohesive and noncohesive
sediments,
--Mathematical and physical models of water-quality
parameters,
--Two- and tbree-dimensional models of short waves and
wave-current interaction in port entrances.
This list is neither inclusive, exhaustive, nor ordered by priority.
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5.
DISPOSAL AND USES OF DOMED INTERIMS
The questions to be answered in this area include:
--Accumulation in the food chain of the toxic
substances in dredged materials, and the possible
effects on human health;
--Alteration of the biological-resource value of
subtidal bottoms owing to dredging and disposal
operations;
--Dynamics of dredged materials in open water: Where
does it go after disposal? Does it stay put or move?
--Relationships between dredge-disposal islands,
the alteration of traditional flow patterns, and
consequential biological effects on estuarine
organisms;
--Effects of deep-water disposal on benthic communities
and biochemical cycles;
--Potential methods of increasing the productivity of
bottoms through the controlled use of dredged
materials;
--Alternative uses of dredged materials--for example,
beach nourishment, and fill acquisition;
--Use of dredged materials for the development of
needed habitats;
--New methods for reducing dredging costs;
--Effective dissemination of the results of the
Dredged Materials Researab Program carried out by the
Waterways Experiment Station; and
--Processing and treatment of dredged materials for
disposal.
Research Objectives
The research program addressing these questions should determine
the susceptibility of various levels in the food chain to the toxicants
present in some dredged materials,
and develop:
--Predictive models for the fate of various components
of placed materials,
--Productive uses of dredged material for recreational
islands, habitat-replacement projects, development
of marshes, and nourishment of beaches; and
--Methods for reducing dredging costs.
The program should seek wider dissemination of the results of the
Dredged Materials Research Program of the U. S. Army Corps of Engineers.
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162
6. EPt)STON, TRANSPORTATION, "D DEPOSITION
GRANULAR SEDIMENTS
Improved procedures are needed for the prediction of shoaling rates
and patterns near harbor entrances. The methods offered to answer this
need should be based on wave, wind, and current characteristics. The
results should include the development and verification of appropriate
field methodologies.
Research Objectives
The researob program directed to these procedures and methods
should seek improvements in:
--Measurement of the quantities and characteristics of
littoral materials;
--Measurement and quantification of longshore energy--
waves, currents, and winds; and
--Understanding of the mechanics of waves and
sediments, and of the interactions of waves,
sediments, and structures.
A principal objective of the research program should be the improvement
of predictive models.
7 . ENTRANCE-CHANNEL DES IGN AND OPERATING CRITERIA
Improved criteria are required for the siting and design of harbor
entrances. Such criteria must include:
--Ship types, sizer, and traffic densities,
--Appropriate aids to navigation, and
--Expected operating equipment, in terms of wave",
currents, winds, and tidal range.
Data for existing and projected entrance channels are insufficient to
predict:
--Waves, swells, and sea conditions,
--Currents,
--Tidal heights,
--Salinity,
--Sinkage and trim,
--Vertical ship motions,
--Vessel draft, and
--Bank effects.
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Researab Objectives
To develop improved criteria, the following needs for research and
development must be met:
--Determination of the sophistication necessary for
adequate simulation of harbor-entry maneuvers to set
harbor-design parameters;
--Further development and validation of mathematical
models of ship-maneuvering motions for use in
simulations of harbor-entrance transits. Such models
must adequately account for effects on ship motions
on waves, currents, wind, water-depth
irregularities, and irregularities in the proximity
of the banks;
--Establishment of mathematical expressions for the
horizontal dimensions and siting of channels in
simple harbor entrances as a function of design ship
characteristics;
--For more complex harbor entrances; e.g., with shear
currents,* selection of the best methods and
procedures for studies directed to fixing the
horizontal dimensions;
--Development of a mathematical formula to enable
prediction of acceptable ship sizes and load
conditions for given wind, tidal, sea/swell
measurements, based on the horizontal dimensions
of the entrance; and
--Similarly, development of statistical formulae to
enable prediction of acceptable drafts.
8. STANDARDS OF SAFETY
There do not exist accepted standards, analytical techniques, or
data for systematic evaluation of the navigability of harbor entrances.
Research Objectives
--A historical analysis should be performed to
determine the safety records of each existing major
port. Those with the best and worst safety records
should be identified and studied further.
*A shear current varies locally for example, sweeping across the mouth
of a harbor faster than its uniform speed elsewhere. If a ship
intersects a lateral shear current, the bow will feel the current most,
with a tendency to turn the ship.
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--A careful
examination of these ports should be
conducted, using modern port-design techniques, to
determine the characteristics that enhance safety
and those that lead to safety problems.
--Techniques for measuring these characteristics by
reference to a common base need to be developed by
experts in various disciplines (perhaps constituting
an advisory board). A set of standards should be
developed from these efforts to support adequate
evaluation of the safe navigability of an arbitrarily
selected port, and should be cast in a form that can
be used in systems design.
--The standards should be promulgated by an
independent, authoritative source.
9. MARINER NEEDS
The needs of the mariner should be defined in quantitative terms.
These needs include (but are not limited to):
--Dependability and usefulness of aids to navigation,
--Accuracy and usefulness of charting services,
--Vessel-maneuvering requirements, and
--Vessel support services.
Research Objectives
The research program designed to investigate and quantify the needs
of the mariner should:
--Develop and validate mathematical models of vessel
behavior characteristics and the effectiveness of
aids to navigation;
--Conduct studies of the human-factors aspects of
vessel control, and of the use of charts and aid; and
--Combine the results of these and other studies to
develop simulator and physical models of existing and
projected harbor entrances.
10. DECISION MAKING PROCESS
-
The decision making proce"s for harbor entrances should be reviewed
to enable evaluation of proposed improvements to harbor entrances, and
if these improvements are indeed needed, to enable permits to be
obtained and work initiated promptly.
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Research Objectives
--Research case histories of delays in proposals for
changes, or for new entrances to harbors, to assess
the part played by the decision making process;
--Develop and test alternative decision making methods,
including non-adversary methods; and
--Develop a plan for effectuating legislative action
through more effective processes.
11. EVALUATION OF COASTAL-RESOURCE VALUES IN HARBOR SITING, AND
RESTORATION OF HAB ITATS
Natural-resource values should be evaluated to ensure their proper
consideration in siting and design of harbors: their determination,
evaluation of their significance, and assessment is essential to
achieving proper balance among environmental, economic, and other
social values in decision making.
Research Objectives
--Determine why wetlands and coasts are productive,
--Investigate the origins and evolution of wetlands
and coasts; and
--Establish the ecosystem response to natural events
and human activities.
REFERENCES
1. Van de yen, Andrew H., and Andre L. Delbecq, "Nominal versus
Interacting Groups for Committee Decision-Making Effectiveness,
Journal of the Academy of Management, 14 (June 1971~.
2.
, A group
process model for problem identification and program planning,"
Journal of Applied Behavioral Science, 7 (1971~: 466-492.
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Representative terms from entire chapter:
dredged materials
