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(2) LITTORAL DRIFT
'THE DrAINAGE OF FENS ANd LOW LANdS BV GRAVITATION ANd STEAM TOWER,'
LONGMANS, GREEN, AND CO.
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At frequent intervals attention is directed to the inroads made by the sea on the cliffs which border the shores of this country, and to the injury done during gales and high tides to sea-walls and other works which have been constructed for the protection of lands adjacent to the coast.
The means taken to prevent similar disasters, and generally for the protection of the coast, are as diverse as many of them are ineffectual. In no branch of engineering, perhaps, is there so little unanimity of opinion, or in which so much money is from time to time expended on works that are useless. Even in Holland, whose existence depends on the maintenance of its sea-walls and defences, the authorities are divided on most important questions both of principle and practice; and consequently methods of protection which find favour in one part of the coast are condemned as costly and ineffectual by those having charge of the defence of adjoining parts.
The author having directed his attention for several years past to the subject of coast erosion and littoral drift, and the various means pursued in protecting the coast, and having inspected the greater part of the coast of this country—from Northumberland on the east to Cumberland on the west—and also the shores of Holland, Belgium, and France, on the opposite side of the North Sea, has had opportunities afforded him of becoming acquainted with the various means that have been pursued to prevent the destruction of beaches and the protection of sea-walls and other defences.
In the following chapters will be found recorded the results of the experience thus obtained, together with a description of the devastation that is taking place along the shores of this country and on the opposite Continent, and of the protective works that have been carried out on the coasts of England, Belgium, and Holland.
Any principles stated or deductions drawn must only be considered as applying to these shores, or to tidal coasts having the same characteristics.
Before determining the design of works for coast-protection, it is essential that due consideration should be given to the laws that govern the action of waves breaking on the shore, and the effect produced by them on the beach, and on sea-walls and groynes; and also of the conditions under which material is drifted along the coast. These subjects have therefore been fully dealt with in the earlier chapters. The examples afterwards given afford an opportunity of contrasting the results of the different systems of coast-protection that have been adopted, and will enable a more correct conclusion to be arrived at from the lessons taught by experience than by following only theoretical laws.
The purpose of the book is not to advocate any special system of groyning or coast-protection, but to afford such information as to the varying geological and tidal conditions attaching to sea coasts, and the result of protective works carried out under different degrees of exposure, as may be of service to those having charge of protective works, or interested in the destruction and preservation of land bordering on the sea.,
The question of littoral drift as affecting bars and harbours has already been dealt with by the author in papers read at the Institution of Civil Engineers;1 and that of the action of waves
1 "Ban at the Mouths of Tidal Estuaries," Minutes of Proceedings Institution of Civil Engineers, vol. a, 1889; "Littoral Drift in Relation to River Outfalls anil Harbour Entrances," idem, vol. cxxv., 1896.