The Telegraph-courier. [volume] (Kenosha, Wis.) 1888-1946, 1897-05-06

| storm, ana any OBSTRUCTION ike pier
in that depth will produce modifica-
ton of the forces and of the bottom
around its outer end. This modifica-
ton is shown 10y all the surveys made
at the harbor Of Kenosha.
The material of the lake bottom in q
! feet and lesser depths on the western
shore of the lake is sand and silt, with
some gravel, and is readily rolled or
carried in suspension from one place to
another. Great quantities of sand are
transported fact, are in constant
motion. Accessions are also constantly
being made, by erosion along the bluffs,
which in some places recede at the rate
of from II feet to 16 feet per year.
The forces at work produce three
forms of deterioration, (D shoaling
between the piers, (2) a general ad-
vance of the foreshore to and beyond
the ends of the piers, and (3) bar
across the entrance.
The problem of lake harbor inn
provement is therefore to maintain a
uniform depth at the channel entrance
and a uniform depth in the channel
The material producing the firstform
of deterioration comes from several
sources: (1) Sediment brought down
by the river, (2) sand brought over the
piers by wind, (3) sand carried through
the piers by waves, and (4) sand car
ried in suspension from the lake
/ II
currents. The current of the river is so
small that the scour on the bottom is
comparatively little, in fact may be
disregarded, and the sediment finds IL
resting place at that point where still
water is created by the meeting OF the
river and the lake. There is no prac-
ticai method of preventing this deposit.
The material brought in from the lake
through the entrance also finds rest
ing place at the same point as that just
mentioned. A further extension of the
piers may diminish the amount OF ma
teria brought in, but to prevent it
altogether would require their extension
beyond the reach of sand bearing cur
1 rents, and be far more expensive than
to remove the deposit by dredging.
By making the piers tight another
source of deterioration is cut off, and
the only practical method of preventing
sand from coming over the piers is the
erection of sand fences, which are, after
all, only temporary expedients. 1t is
easily seen, therefore, that dredging
between the piers will be required an
nually to maintain the channel. 1t is
impossible to say from the data on
hand what the amount will be, and it
will vary considerably from year to
year on account of changing weather
conditions.
The advance Of the foreshore and the
| formation of the bar in front of the
entrance are much more difficult to
deal with. In fact it can not be shown
from the imperfect data just why they
take place or just what methods should
be employed to prevent their occur
renee. | am OF the opinion that they
are connected by being the results of
the same cause acting at different
places. In order to determine the
proper direction, length and relative
position of the piers it is necessary that
this information should be at hand, and
it can only be supplied by extended
surveys and observations upon winds,
waves and currents. While the north
pier has constantly been in advance Of
the south pier, it can not be stated
positively that the bar would not be
formed if the conditions had been re-
versed. In extending the piers the
additions have been made to the north
pier first, probably in order to afford
shelter for vessels entering the harbor
during northeast gales. Whether the
harbor would be as easy of entrance
with longer south pier, | can not say,
but it seems that if the object of pier
construction be to provide and main
tain a navigable channel, it should not
be made to include the additional pur
pose of providing shelter, especially
when 1t may be true that both objects
can not be fulfilled at the same time.
The questions to be solved in order
to decide how to maintain constant
depth at the entrance are the follow
ing: What causes the advance of the |
foreshore Can point ever be
reached by extending the north pier
where no further accumulatiOns will
take place about its outer end, or will
there be constant advance What
causes the formation of the bar in front
of the entrance Can it be prevented
by extension of the piers, or must the
piers be arranged in different manner
from the present system, i. e., parallel
and of equal length
There are almost no facts at hand to
assist in the solution of these questions
beyond knowledge of the existence of
the before mentioned general currents,
the meteorological data, and the few
and very incomplete surveys.