A Treatise On The Principles And Practice Of Harbour Engineering

CHAPTER IL HARBOUR DESIGN. Difficulties of the Subject—Classification—Definitions—Roadstead—Harbour—Basin—Dock Harbours of Refuge—Commercial Harbours—Fishery Harbours—Localisation—Coastal and Inland Ports—Procedure in Design of Harbours—Preliminary Considerations— Natural Phenomena—Prevalence and Intensity of Storms—Coastal Change—Accretion and Denudation—Effect of Artificial Interference—Influence of Effluents—Island Harbours—Harbour Areas and Entrance Widths—Illustrations of Harbours at Zeebrugge, Queenstown, Sandy Bay, Sunderland, Peterhead, Libau, Madras, Whitby, and elsewhere. Difficulties of Systematic Treatment.—That maritime engineering is a Science of much complexity and no little incertitude, is but a trite remark to make. It will be admitted, without any controversy, that its operations are of necessity fouuded largely upon assumption and carried out by tentative rather than confident measures. Hypothesis, analogy, and experiment con- stitute its working basis, alike in regard to theory as to practice, to design as to execution. The whole field of it is beset by many and peculiar difficulties, and scarcely any other department of constructive work finds so many hazards and obstacles in the way of satisfactory accomplishment. 'l'he task of the engineer who sets himself to contend with the almost bewildering array of antagonistic forces incidental to maritime operations, is exacting in the extreme. The data upon which his calculations must perforce be based are often defective and their origin obscure. He has to deal with agencies not only conflicting but frequently also co-operative, and as destructive as they are capricious. His work is subjected to the most trying of all ordeals, in that it is constantly exposed to the risk of unascertainable possibilities. Occasions arise when the profoundest sagacity and the ripest expcrience may well prove to be at fault. Laws which hold good in one locality seemingly reverse themselves in another. The success of certain dispositions in one case is no guarantee of their efficacy elsewhere, still less justification for their general application. Each place has its own definite characteristics, its peculiar defects, and its special advantages, differentiating it from all other places. There is no uniformity, and very little similarity. Generalisation therefore, is impossible, and classification becomes difficult. Yet, in spite of these deterrent considerations, it is manifest that some system of treatment must be adopted, unless the principles of harbour engineering are to rest on a haphazard, heterogeneous basis, contrary to the 8