A Treatise On The Principles And Practice Of Harbour Engineering

HARBOUR DESIGN 17 Fishery Harbours.—Fishery Harbours, though a numerous dass, are not, generally speaking, constructionally important, but they possess characteristics sufficiently notable to merit some attention. In the first place, the scareity of capital available for artificial operations renders it necessary to take the utmost advantage of natural features. Then, since fishermen require a maximum amount of time for their expeditions, with a minimum of delay in despatching their hauls, on account of the perishable nature of fish, every facility should be afforded them for making the harbour at the last possible moment consistent with the state of the tide. This inter- mittent accessibility, however, characteristic as it is of all tidal harbours in Fio. 9. —Entrance to Langston Harbour. Direction of currents. The numerals represent hours of ebb and flood tide. which vessels take the ground at low water, or where there is a shallow bar, is inimical to the interests of sea fishermen. Their requirements demand a harbour constantly open for arrivai and departure alike. A shoal of fish may be missed as easily from sheer inability to proceed to sea as from the deterrent effect of impending foul weather.1 The entrance of a fishery harbour, while not unduly wide, must not be made too narrow. It is liable to be tbronged at times by craft anxious to enter in order to escape a rising gale, or to catch the early market. Cases 1 Depths below low-water level of ordinary spring tides at some of the more important fishery harbours in this country are: —-Hartlepool, 15' ; Aberdeen, 14' ; Dundee, Yarmouth, and Newlyn, 12' ; Lowestoft, 10'. The majority of fishery harbours, however, have depths much less than these, and, in many cases, they become practically or actually dry at low water. 9