SHINGLE BANKS
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erosion has taken place on the north side of the harbour, due to the arrest of the normal column of travelling sand, and whole towns and villages have thus been swept away. This experience is an extreme instance of the action which goes on in a greater or less degree at every headland, river mouth, or solid projection from a foreshore into the sea.1
   The ameliorative artificial works by which a coast-line is maintained are in the main sea-walls and groynes. Stability may also be assisted by fostering the growth of foreshore vegetation. When once such vegetation has secured good hold of a coastal area, its effects materially aid the preservation of artificial works. The bane of coastal defence is often the procrastination of landowners and local authorities. In numberless cases action has been deferred until the
problem of defence has Fig. 3JA.— Madras Harbour—Change in Low-water Line
become tenfold more
acute than it would otherwise have been. Moderate expenditure on preventive measures are postponed until costly remedial measures become necessary. It has often happened that a shingle bank has existed and acted as a barrier of defence such that, had steps been taken to avert its dispersal, this state of affairs would have continued for an indefinite time. The comparatively small expenditure necessary for securing this object, however, has not been forthcoming, with the result that such shingle bank has been spread, and its crest lowered, so that it no longer acts as a line of defence in heavy gales. Extreme weather conditions are what do the mischief in such cases. In a single tide, a protective barrier of this class may have its
Q 5p0 O_rooo_2000 FEET
    1 “The Sanding-up of Tidal Harbours” (A. E. Carey), Proc. Inst. C. E., Vol. CLVI, pp. 1-90.
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