Improved Method of and Means for Removing and Preventing the Formation of Sand Banks or Bars at the Mouths of Rivers, Harbours, and other Estuaries.
Year: 1893

page_text: Date of Application, 1st Dec., 1893
Complete Specification Left, 13th June, 1894-Accepted, 14th July, 1894
PROVISIONAL SPECIFICATION.
Improved Method of and Means for Removing and Preventing the
Formation of Sand Banks or Bars at the Mouths of Rivers,
Harbours, and other Estuaries.
I, ANDREW ENKEL PAKEMAN of East London, in the Colony of the Cape of
Good Hope, Gentleman, do hereby declare the nature of this invention to be as
follows:-
This invention relates to a means of removing sand banks or bars formed at the
entrances to harbours and the mouths of rivers and other similar places, and of
preventing their formation in the future, the invention being particularly applicable
to certain localities where the conditions are such as hereafter referred to. :
I have discovered by observation that at the Port of East London there are two
currents opposed in direction and at different levels, viz. an upper warm current
coming from the Tropics and a subjacent cold current from the Antarctic Region,
and that the sedimentary deposit which forms the bank or bar at the mouth of the
said harbour is brought there by the warm tropical current and that its precipitation
from the water in which it is suspended is due to the effect of the opposing colder
current under the existing conditions.
My invention has for its object to provide a means whereby the natural force of
this lower current, which is itself quite free from the sedimentary deposit, may be
turned to account and so applied as to produce a scouring action which will have
the effect of clearing away the existing bar or bank and prevent it again forming.
Having ascertained that the upper warm current is the vehicle by which the
sedimentary deposit is brought to the spot, it is of prime importance that the means
adopted for diverting the lower cold current should be such as to interfere as little
as possible with the course of the upper current and should so divert the lower
current as to produce a strong scouring action in the seaward direction.
The invention consists essentially in the provision at one side of the river mouth,
harbour, or other place to be scoured, viz.: at the side from which the lower cold
current approaches, of a submerged breakwater or equivalent structure of such a
height as to divert from its natural course only the lower-cold current whilst the
upper warm current can flow freely over it, this breakwater or equivalent structure
lying in such direction, having regard to the configuration of the land, the set of
the currents, and other conditions of the locality, and being situated at a distance
from the shore, that the lower cold current will be diverted and caused to flow
between it and the shore.
In combination with this submerged breakwater, a training wall or breakwater is
provided at the opposite side of the river mouth or harbour by which the current
which has been diverted as above described is caused to take a seaward direction
transversely to the direction of the upper current, so as to continually produce a
strong scouring action on the bottom and carry off the deposit as fast as it is
precipitated from the upper warm current.
Dated this 1st day of December 1893.
A. E. PAKEMAN,
By A. M. & Wm. Clark,
53, Chancery Lane, London, Chartered Patent Agents.

page_text: Improved Method of and Means for Removing and Preventing the
Formation of Sand Banks or Bars at the Mouths of Rivers,
Harbours, and other Estuaries.
I, ANDREW ENKEL PAKEMAN, of East London, in the Colony of the Cape of
Good Hope, Gentleman, do hereby declare the nature of this invention and in what
manner the same is to be performed, to be particularly described and ascertained
in and by the following statement :-
:-
This invention relates to a means of removing sand banks or bars formed at the
entrances to harbours and the mouths of rivers and other similar places, and of
preventing their formation in the future, the invention being applicable to certain
localities where there is an under cold current herein referred to as the polar
current and which although variable is more or less distinct from surface currents.
Thus, for instance, I have discovered by observation that at the Port of East
London, Cape Colony, there are generally two currents opposed in direction,
vis. an upper warm current coming from the Tropics and a subjacent cold current
coming from the Antarctic Region, and I have further discovered that the
sedimentary deposit which forms the bank or bar at the mouth of the said harbour
is due to the dead water resulting under the existing conditions.
:
My invention has for its object to provide a means whereby the natural force of
the lower current may be turned to account and so applied as to produce a constant
and powerful scouring action seawards, which will have the effect of clearing away
the existing bar or bank and prevent it again forming.
The invention consists essentially in the provision at one side of the river mouth,
harbour, or other place to be scoured, viz.: at the side from which the lower cold
current approaches, of a low breakwater adapted to act as a "training wall" for
the lower current, this combined breakwater and training wall being situated at a
short distance from the shore low water mark and extending seawards at such an
angle to the set of the currents along the shore that the lower cold current will be
diverted towards the mouth of the river &c., and caused to flow between the
breakwater and the shore into the mouth of the river, harbour or estuary where it
is diverted seawards by a training wall. or breakwater at the opposite side of the
river mouth or harbour so that it will continually produce a strong scouring action
on the bottom. The face of the breakwater opposed to the surface current is also
inclined in such direction that this current will be diverted seawards without
materially checking it so as to prevent the formation of "dead water" which
would cause sand to deposit.
The existence of these upper and lower currents more or less opposed in direction
is not limited to the Port of East London, but they prevail on all ocean coasts
exposed to the influence of a polar current.
The accompanying drawing, forming part of this Specification, illustrates in an
elementary manner the principle of my invention, but it must be understood that
the mode of carrying it into effect may be modified in detail to suit the exigencies
of the locality in which it is applied.
The drawing represents the mouth A of a river or harbour across which a bar is
now formed at B. The arrow C indicates, approximately the direction of the
warm upper current and the arrows D indicate, more or less approximately, the
general direction of the cold lower current. E is the combined breakwater and
training wall placed at the side of the river or harbour mouth from which the
cold current D approaches, and inclined in such direction as to divert the current D
towards the mouth of the river &c. and cause it to pass through the water-way F
between the breakwater and the shore, as indicated by the arrow D. Gis
another training wall at the opposite side of the river or harbour mouth and in

page_text: such position as to cause the current D' entering through F to be deflected
seawards, as indicated by the arrow D'. The face of the breakwater E which is
opposed to the current C is also inclined so as to direct this current seawards, as
indicated by the arrow C¹.
Having now particularly described and ascertained the nature of the said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is :-
The herein described method of, and means for, preventing the formation of
sand banks or bars at the mouths of rivers, harbours, and estuaries, exposed to
currents more or less opposed in direction at different levels.
יווי
حيمد
A. E. PAKEMAN,
By A. M. & Wm. Clark,
53, Chancery Lane, London, Chartered Patent Agents.