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20
HARBOUR ENGINEERING
observations himself, in reference to varions natural and meteorological
phenomena, and the following will specially claim his attention :—
Fig. 11. —Wind Diagram. Frequency ordinates
set off from centre; intensity ordinates from
radial lines.
from a certain point of the compass.
most frequent, it must not, by any
wind which is most to be feared.
A single gale arising from a
totally different quarter may
cause more havoc and destruction
than a whole twelve-month of the
prevailing wind. The import-
ance of the latter lies rather in
the effect it has upon- the coastal
contour in its relationship with
other agencies, the effects of
which, though momentarily in-
significant, are continuons and
cumulative. Such
the ebb and flow
and the erosive and
power of currents.
agencies are
of the tide
transportive
Ways of recording wind fre-
quency and intensity are numer-
ous. Three examples are shown
in figs. 10, 11, and 12, with explanatory notes. Time ordinates are not
difficult to plot, possessing, as they do, a direct numerical value. It is a
different matter with the intensity ordinates, whicli have to be to a certain
1. The direction and intensity
of the winds and the frequency
of storms.
2. The height and force of
the waves.
3. The range of the tides.
4. The direction and velocity
of the currents.
5. Evidences of silting, littoral
drift, or coast erosion.
6. The extent of exposure and
the maximum “ fetch.”
With reference to the first of
these features, it may be pointed
out that nearly every place is
subject to what is called a Pre-
vailing Wind, that is, a wind
blowing with great constancy for
a considerable portion of the year
But while the prevailing wind is the
means, be concluded that it is the
Fig. 12. —Wind Diagram. Frequency ordinates
set off from centre; intensity ordinates from
circumference.