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INTRODUCTION Robert L. Wiegel Chairman Panel on Harbor/Port Entrance Design Throughout history, engineers have been concerned with ships, ports, aids to navigation, land reclamation, the protection of coasts from erosion, and the design of structures to withstand the great forces of the ocean during storms at sea. Engineering works are not constructed as an end in themselves. They are made for the economic and other social benefits of people, for military reasons, or for both. Thus, the conception, planning, design, construction, and operation of these works, and the development and management of the systems of which they are a part, have always been carried out in concert with broader plans. The significance of harbors, therefore, is a distinctive element woven into the culture and politics of peoples and nations." This has been so since the time of the Minoan civilization of remote antiquity. 2/3 Owing to the extensive use of shipping and harbors for more than 5000 years, it is evident that harbors have been, and still are, a major factor in the development of civilization . Harbors, ports, and ships are essential to the movement of ideas, techniques, and goods from one place to another. What is a port, and what is a harbor? Many times the words are used interchangeably, as ports are often constructed within harbors. A study of the definitions of these words, together with words of similar roots, indicates that a port is a place where cargoes are loaded or unloaded, and a harbor is a place that provides shelter and anchorage for ships. There are ports that are not sheltered and harbors that have no ports. This workshop will be concerned with harbors, and will not touch upon the problems of offshore terminals that are not sheltered. Much of the development of offshore terminals has been brought about by the deep drafts of the very large ships used in the bulk cargo trade. The cost of dredging deep channels and other restraints against traditional harbors are such that offshore terminals sometimes offer a better solution. In some regions, it is relatively easy to have deepwater ports. 4 There are six major types of natural harbors: a well-protected bay, the lee of an isle (today, perhaps man-made) or a rock connected to shore by a tombola, the lee of a reef, the portion of an open bay that is reasonably well sheltered from the prevailing waves by refraction, just upstream from a river mouth, and in the broadest sense 1
2 of a ~harbor, n the beaching of a craft. There are, of course, variations of these. Naturally occurring well-protected harbors are not common, but those that exist, such as Sydney, Australia, are well known. The Phoenicians made use of the lee of small isles just offshore, such as Tipasa, adding moles for additional protection and cargo handling. Port Moresby, Papua New Guinea, is an example of a harbor sheltered by an extensive reef. There are many examples of open roadsteads that are reasonably sheltered from prevailing waves, such as Santa Cruz, California, located on Monterey Bay. The degree of shelter depends on the characteristics of the ships. Thus, many of the large bulk cargo ships in operation today, especially tankers, can load and unload in what might be heavy seas for smaller ships. River mouths have been used and are being used in many parts of the world, not only for the shelter they afford but because the river is a waterway to the hinterland. The Rhine River is a classic example. Beaching is still used in many parts of the world, often for small fishing vessels, owing to the lack of natural harbors and the relatively high cost of artificial harbors. One of the most important and difficult parts of a harbor is the entrance. Many harbor entrances have been found to be difficult for ships to navigate owing to currents, bars, and waves. These problems are not new. The early sixteentb-century sailing directions of Pierre Garcie contain the following warning:5 Know that when the sea breaks more than two rollers on the Plateau de St. Jean de Lux (in the Bay of Biscay) you must not attempt to enter LeBoucaut; take heed indeed, because it's not worth it. But if the seas are not breaking you can go in safely. The entrances of harbors that once had high traffic volume have closed completely. A case history of the closure of such a natural entrance, and its eventual reopening and maintenance is useful to engineers. Such a case, with information dating back to the tenth century A.D., is that of Aveiro, Portugal. 6 Better dredges, navigation aids (buoys, lights, radar, loran), and ship handling now make it possible to improve our harbor entrances. With these improvements, the use of local pilots, and the development of marine traffic control systems, we can now make better use of the entrances. Nevertheless, we are all aware of a number of instances in recent years in which ships have run aground and foundered at a harbor entrance. Several programs are being developed and tested for better control of marine traffic in harbors and in the sealanes near the harbors. These developments are of great importance to high-density shipping harbors, and effecting them successfully is a major challenge. They must be coupled with improvements in the maneuverability of ships and barges in restricted waterways, improvements that demand greater ability to analyze the motion of ships in these conditions.
3 In contrast to the high-density harbors employing advanced technology are those of such low density and economic activity that little can be done. One common type is the harbor just inside the mouth of a river. The successful use of such harbors often requires the design and use of special types of small ships that can regrounds on bars without much damage. A major challenge to the engineer i" the development of inexpensive and reliable navigation aids for the entrance and passages of these natural harbors. To do their jobs properly, engineers need to be able to predict reliably the quantitative as well as the qualitative effects of the system consisting of a harbor layout, its structural appurtenances, and the ships that use it. As an example of the type of problem that still exists, consider model studies of sedimentation at harbor entrances. Many studies have been made, and many idea" have been tried to solve the problem of making quantitative predictions (including the time-rate) of what will happen to sediments at and near a natural, man-modified, or artificial entrance to a harbor. The problem is difficult when only waves and tidal flows are considered. In a recent paper, Kamphuis concludes for hydraulic models: 7 After a number of years of study, coastal mobile bed models are classified and scale effects resulting from various non-similarities are discussed. Two methods of classification are given--one according to non-similarity of basic scaling relationships and another according to the type of model required. All but one class of model is subject to substantial scale effect and thus no easy scaling recipes can be given. Modelling still remains an art and this extensive study only results in pointing out some common pitfalls to be avoided. Models using lightweight material are shown to be eminently unsuitable for inshore areas and it appears to be virtually impossible to determine time scales for bed morphology because of scale effect. The simple tracer model appears to yield best value for money invested. When harbors are located in estuaries, density flows exist and the rivers usually transport sediment into the harbor. The problems are much more complex than for the "simpler case considered above. The development of reliable tools to analyze the interaction of ships, waves, tides, currents, river flows, and sediments, together with the effects of structures and dredging operations (including dredged sediment disposal) from the standpoint of harbor design and ship operation is a very challenging problem for us today.8 In addition to the natural harbors, man has constructed artificial harbors, components of natural harbors, and improvements. Some of the problems of entrances of both natural and artificial harbors will be considered at this meeting.
r 4 Purpose and Objectives of Meeting The subject of this three-day meeting is the design of harbor/port entrances for safe, efficient use. The harbors and ports to be considered are those used by ships engaged in international or intracoastal trade (or both). The objective of the workshop is to identify the principal problem areas, to assess the state of our knowledge, and to recommend the research needed to transform the nearly empirical approach used today to a completely rational design procedure for entrances to ports and harbors. A completely rational procedure would consider the requirements of the following five functions: the economic vitality of the United States, the needs of the users, harbor/port operations, ship operations, and the environment. Definition of Harbor/Port Entrance Basic procedural rules for this meeting were formulated by the panel. First is a narrow definition of harbor/port entrance. The panel decided that for the purpose of this workshop the entrance of the harbor/port is that region of the ship channel between the open sea (or large lake) and the protected region of the harbor. On the seaward side, it includes the nearby approach fairways, and on the harbor side, ~_ , , sufficient distance to permit a ship to stop. Seaward of the "entrances there is essentially unlimited space and water depth from the standpoint of ship traffic. Shoreward of the "entrance, the space and depth are generally greatly restricted. The panel decided that a more detailed definition would not allow the flexibility needed to consider many different harbor and port types. Presentations The formal presentations to follow this introduction and the keynote address on harbors and ports are grouped in three areas of concern: those pertinent to the design and maintenance of harbor/port entrances, those of the ships and users, and those of nature and the environment. The subjects to be considered in each area of concern are: in Design and Maintenance, the principal considerations for design, rules and regulations governing entrances, and aids to navigation; in Concerns of Ships and Users, shipboard aids to navigation and channel width, ship controllability, and other concerns of ship operators and pilots; in Nature and Environment, sedimentation, tidal hydraulics, waves, and the effects of ports and harbors on the environment.
5 Identification of Problems The workshops, using an interdisciplinary approach, address three broad technical areas: harbor/port entrance hydraulics, ship/harbor interaction, and sediment transport-deposition/scour. Each of these areas requires detailed consideration of a number of technical subjects, listed below. (Those common to more than one broad area are marked by an asterisk.) Harbor/Port Entrance Hydraulics Fluid hydrodynamics Wave climate (including sballow-water directional spectra) Hurricanes Hydraulic models Harbor surging Entrance structures* Coastal zone management* Data acquisition* Environmental effects* Ship/Harbor Interaction Ship hydrodynamics Navigation aids (including real-time environmental data) Pilots Tug operators Ship control Free-running ship model Casualty studies Salvage (including contingency planning) Small boats Vessel Traffic Safety Systems (VTS) Coastal zone management* Port authority Environmental effects* Propeller wash Sediment Transport-Deposition/Scour - Sediment transport-deposition/scour (sand, silt, clay) Dredging Entrance structures* Movable-bed models Coastal zone management* Data acquisition* Environmental effects* Fisheries Workshop participants were encouraged to write short statement" of the problems they considered most important in barbor/port entrance
design. These were then studied by the participants, who each listed the ten most important or urgent, in order. After the final tally, small groups assisted rapporteurs in drafting the workshop's statement of each problem and the needed researab or action. These statements were reviewed in plenary session, where additions or minor changes were made where approved by all participants. References 1. Bowen' E. G., Britain and the Western Seaways: A History of Cultural Interchange through Atlantic Coastal Waters (New York: Praeger, 1972~. Casson, LThe Ancient Mariners! Sea Farers and Sea Fighters of {New York: The Macmillan Co., the Mediterranean in Ancient Times 1959). 3. Marinatos, Spyridon (text) and Otis Imboden (photographs), "There, Key to the Riddle of Mines, National Geographic, 141 (May 1972): 702-726. 4. Wiegel, R. L. and Kiyoshi Hor ikawa , "Coastal Eng ineer ing in Japan," Civil Engineering, 34 (December 1964~: 76-77. 5. Waters, D. W., The Rutters of the Sea: The Sailing Directions of Pierre Garcie (New Haven, Con no Press, 1967~. 6. Yale University Abecasis, Carlos Krus, "The History of a Tidal Lagoon Inlet and Its Improvement (The Case of Aveiro, Portugal) , ~ Proceedings of the Fifth Conference on Coastal Engineering, Grenoble, France, September 1954, J. W. Johnson, ed. {Berkeley, California: Council on Wave Research, The Engineering Foundation, 1955), pp. 329-363. 7. Kamphuis, J. William, "Coastal Mobile Bed Model--Does It Work," Symposium on Modeling Techniques, San Francisco, California, September 3-5, 1975, Vol. 2 {ASCE, 1975), pp. 993-1009. 8. Wiegel, R. L., Tithe Significance of Harbors, Symposium on The Present-Day Challenge of the Sea, n Dedicated to John W. Hupkes, Wageningen, The Netherlands, May 13 and 14, 1976, Netherlands Ship Model Basin Publication NSMB515, 1976, Chapter III.
