Coastal Sand-Travel Near Madras Harbour. (Including Plate at Back of Volume).

Abstract

SPRING ON COASTAL SAND-TRAVEL [Minutes of north of the harbour. The erosion, however, has been checked, a t the place where land is valuable, by revetting the shore with loose stone, for a distance of about 12 mile, at the rate of 200 or 300 cubic feet per lineal foot. Beyond this revetment the land liable to be eroded is scarcely worth the cost of revetment; and at all events the High Courts of Justice have laid it down, in three successive decisions, that the Port Authority is not liable. EARLY OBSERVATIONS. On forwarding to the Secretary of State for India, in 1874, the proposal for an artificial harbour at Madras put forward by the, late Mr. W. Parkes, M. Inst. C.E., the Government of Indin remarked :-1 "We believe that considerable uncertainty must always attend conjecture aR to the effect of harbour works upon the movement of sand on an open foreshore like that at Madras, but we do not consider that the possibility of the proposed harbour being liable to Bilt up is a conclusive objection to the projected scheme, unless, indeed, the objection be considered sufficiently strong to negative any attempt to provide shelter for the port of Madras." On receipt of the dispatch containing this extract, the Secretary of State propounded to the late Mr. J. F. La Trobe Bateman, Past-President Inst. C.E., the following question, inter crlia, :-" Whether the obstruction to the littoral currents ofFered by the break-\vater is likely to cause an accumulation of sand ; and, if so, within what period such accumulation is likely to impede the entrance to the harbour." Replying to this question Mr. Bateman wrote :-" A breakwater or pier projecting at right angles from the coast must of necessity obstruct littoral currents and arrest travelling sand or shingle, but I have no information as to the quantity of sand which wouM be thus arrested in a year, and cannot therefore make any calculation of the period within which the accumulation would extend as far out as the points of the piers, or impede the entrance to the channel. The piers or sides of the enclosed harbour are proposed to be extended nearly two-thirds of a mile from shore, and I am of opinion that, whatever may be the quantity of sand which will be arrested, a very long period will elapsP before the accumulation behind t,he walls can have an injurious effect, so long, indeed, that it may be disregarded." * Selections from Records of the Government of India (P.W.D.), Serial No. 5 , 1885, p. 61. P Ibid., p. 66.