reservoirs of sufficient size to hold all or a greater part of the
waters which run over the surface during and after storms. This plan is
not practicable except where valleys or plains are inclosed by high
ridges and these ridges approach sufficiently near each other to admit
of the economical construction of a bank or dam across the gorge or bed
of the stream which flows through, so that the inclosure will be
complete and form a water-tight basin. Where such a reservoir exists the
water can be held back and gradually let down through properly provided
gates so that the channel will not be flooded.
For flood purposes alone it would be necessary to provide reservoirs of
sufficient capacity to contain the run-off waters resulting from the
largest storms. With such provisions it would be necessary to entirely
empty the reservoir as soon as possible after a storm had passed and
leave its full capacity available for the next storm. It is therefore
better, wherever possible, to provide a reservoir capacity considerably
larger than that represented by the run-off from the heaviest storms, so
that water may be stored for use as power or domestic supply. With such
provision it is necessary merely to draw from the reservoir water to a
depth equivalent to the stream run-off in the drainage area above.
The second plan for prevention of flood damages involves provisions for
letting the flood water out rapidly by removing obstructions to its flow
by straightening and deepening the channels and providing long
embankments, dikes, or levees which rise above the ordinary river level
to a height exceeding that of the stream during its highest floods. This
plan is most generally followed in the case of large rivers like
* * * * *
U. S. GEOLOGICAL SURVEY WATER-SUPPLY PAPER NO. 92 PL. VI
[Illustration: _A._ DEVASTATION IN HEBREW QUARTER, PATERSON, N. J.]
[Illustration: _B._ A COMMON EXAMPLE OF FLOOD DAMAGE.]
U. S. GEOLOGICAL SURVEY WATER-SUPPLY PAPER NO. 92 PL. VII
[Illustration: _A._ INUNDATED LANDS AT PASSAIC, N. J.]
[Illustration: _B._ UNDAMAGED BRIDGE ACROSS PASSAIC RIVER AFTER PARTIAL
SUBSIDENCE OF FLOOD.]
* * * * *
the Mississippi, where the contributing area is enormous and the
conservation of the waters would be impracticable even if the nature of
the country would admit of the construction of reservoirs. In
Switzerland, where the torrents occasioned by the rapidly melting snows
are especially destructive, the flood waters are confined by a series of
parallel dikes on each side of the river, which have the effect of
dividing the flow into several parallel streams. As the main river
channel fills and overflows the inner dikes, the overflow water collects
into the first series of parallel channels, and when a height is reached
at which the second dikes are overflowed the water collects into the
third, and so on. This gives an enormous carrying capacity, the limit of
which is approached slowly, and therefore abundant opportunity is
afforded for preparation upon the part of the riparian owner.
The drainage basin of Passaic River is admirably adapted to the
development of the conservation system. At its headwaters in the
mountains of northern New Jersey are numerous sites for reservoirs. The
comparatively limited area draining into Passaic River makes such a
scheme relatively inexpensive. On the other hand there is abundant
opportunity for effective work in removing obstructions and
straightening and deepening the channel of the lower river. So that, all
things considered, the prevention of flood damages in the Passaic Basin
can be best accomplished by a combination of the two general methods
above outlined.
LOWER VALLEY IMPROVEMENTS.
The channel of Passaic River below Great Falls, at Paterson, is of
limited capacity. To anyone making an inspection, especially within the
city of Paterson, it is readily apparent that the river bed has for
years been considered a legitimate field for encroachment. Owners of
lands fronting on the river have increased their holdings by filling in
beyond the channel line. Buildings have been erected upon these tracts
and the builders have not hesitated to extend retaining walls still
farther into the river bed. Refuse from the city's streets, light and
unstable in character, has been freely deposited upon the bank to be
carried out into the river. Thus the channel has been constricted
laterally, the bottom raised, and there is left for the flood waters no
alternative than that of extending themselves in the upward direction.
It would seem that this, at least, should have been unobstructed. Such,
however, is not the case.
The bridges across the Passaic have apparently been erected without
reference to channel capacity. The authorities have evidently considered
it more important to retain established approach levels than to provide
proper capacity for river water. As an example the following instance
may be cited: During the flood of 1902 a steel truss bridge across the
river in Paterson was carried away. The point of crossing was one of
the narrowest places in the stream and it should have been clear to
everyone that the space beneath the bridge was not large enough to carry
flood waters. It should have been apparent that a new bridge, if erected
at that point, must be higher than the old one, to be thoroughly safe.
Notwithstanding, the new bridge was erected at the level of the old one,
and in addition to this, it was a concrete arch structure, and the great
piers and low arch springs reduced the former channel capacity about 15
per cent. This new bridge, as might be expected, collapsed during the
October flood.
Along the entire course of the stream in the lower valley we find a
continuation of instances of unreasonable encroachment and
ill-considered bridge engineering, and there is opportunity for
relieving a large part of the purely local obstructions by straightening
the channel at chosen points.
Although this matter has not been thoroughly investigated it is readily
apparent to one traversing the river bank that considerable relief may
be secured in this manner. Damage, however, can not be prevented by this
means alone. It would, of course, be possible to erect high and
resistant levees along the entire course of the river, but this would be
extremely expensive and would destroy the water front for commercial
purposes. In fact, such a plan is quite visionary. At the present time
there are no obstructions in lower Passaic River the removal of which
would give relief in the event of floods like those of 1902 and 1903.
When one considers the amount of water which was carried into the lower
valley, the heights which it reached, and the area which it inundated,
the futility of any local improvement except levee construction is
emphasized. The present channel of the river will not carry without
damage the amount of water recently thrown into it, and while it is
important to provide regulations which will in the future prevent
encroachment, and which will correct the evils now present along the
channel, these measures can not, operating of themselves, give relief
from flood devastation. Immunity from flood destruction in the Passaic
must come, if it ever comes, from the construction of flood-catchment
reservoirs in the uplands.
It is not necessary to spend any great amount of time in determining the
cause of floods upon the Passaic. A review of the flood history of this
river shows that in every case floods arise from extraordinary
precipitation. High waters occur through the melting of snows and during
periods of abundant rain. The heavy floods which have been regarded as
extraordinary are clearly the result of unusual conditions of
precipitation. The river carries the usual flood waters, and no damage
is done until the water poured into it is far beyond its carrying
capacity. Therefore the provisions which are made for preventing damage
by floods must, if they be effective, be designed to meet extraordinary
conditions, and means which would prove effectual in ordinary cases
will not stand the test. In order to appreciate the extent of the flood
in the lower valley it is necessary to visit the flooded area and
observe the points of flood height. Unless one does this he will be very
readily deceived when he considers means of flood prevention.
FLOOD CATCHMENT.
Among the highland tributaries of Passaic River there are three
principal areas where storage reservoirs for flood catchment may be
placed: (1) The Ramapo, Wanaque, and Pequanac drainage basins, from
which the waters are carried into the central basin by Pompton River;
(2) the Rockaway drainage basin, and (3) the upper Passaic drainage
basin. The remaining principal tributary of Passaic River, the Whippany,
is not well provided with storage reservoir sites. The combined capacity
of catchment reservoirs which could be constructed in these drainage
areas is considerably more than the volume of the heaviest known
rainfall, that of October 8-11, 1903.
In the description of reservoir possibilities in the following pages the
data with reference to many of the basins are computed from planimeter
and other measurements, the United States Geological Survey topographic
maps being used as a base. The measurements are therefore not of refined
accuracy but suffice for the purpose in view--that of showing flood
catchment possibilities.
POMPTON RESERVOIR.
There are in the Pompton system several sites on Ramapo, Wanaque, and
Pequanac rivers which, if utilized, would afford sufficient storage for
flood catchment purposes, but the entire flow of the river system may be
conserved in what has been described as the Pompton reservoir. This
project was first presented by Mr. C. C. Vermeule in the year 1884, the
details being described at some length in the Engineering News, of April
12 of that year, pages 169-171. In this article Mr. Vermeule presented
the possibilities of Pompton reservoir for use as an additional water
supply for the city of New York, at the time when the Quaker Bridge
reservoir on the Croton watershed was being considered. A few pertinent
quotations from this article may be of interest:
This basin, subdivided by minor ridges which cross it, furnishes
several admirable sites for large storage reservoirs, with
catchments from 50 to 400 square miles in area, lying above on the
primitive rock of the Highlands. About 6 miles of the northeastern
end of the basin is cut off by Hook Mountain, a small ridge of trap
which crosses it from east to west, inclosing a basin 21 square
miles in area, known as Pompton Plains, having its outlet at
Mountain View, 5 miles west of Paterson, at a pass in Hook
Mountain, through which the Pompton River flows to join the
Passaic, 2 miles below. This pass is the gateway by which the
Delaware, Lackawanna and Western Railroad, the New York and
Greenwood Lake Railway, and the Morris Canal enter the plains. The
basin is also crossed near its head, above Pompton, by the New
York, Susquehanna and Western Railroad.
The Pompton River has a drainage area above Mountain View of 420
square miles. It is formed near the head of the basin by the
confluence of the Pequanac from the northwest, the Wanaque from the
north, and the Ramapo from the northeast. * * *
The entire flow from this watershed may be stored by building a dam
across the gap at Mountain View and converting Pompton Plains into
a great lake covering an area of 21 square miles. The elevation of
the river at the gap is 168 feet. The slopes in the basin being
gentle up to an elevation of 220 feet and abrupt beyond it, it will
be advisable to take this as the minimum or low-water level of our
reservoir. It is generally estimated that 25 per cent of the volume
of the mean annual rain on a given catchment is sufficient
reservoir capacity to fully utilize the flood flows. We have long
series of observations of rainfall at three points, which may be
taken to fairly represent the Passaic catchment. At Newark the mean
annual rainfall is 46.2 inches, at Paterson, 50 inches, and at Lake
Hopatcong, 42. The last being on the Highlands, like most of our
watersheds, is perhaps the safest to use. Now, 25 per cent of 42.5
inches, 10.62 inches, which, on 420 square miles, give a volume of
10,362,000,000 cubic feet, the necessary capacity of reservoir.
By raising our reservoir to 240 feet when full we secure a capacity
of 10,493,000,000 cubic feet, or ample to utilize the heaviest
floods of the watershed. This gives a beautiful sheet of water 21.1
square miles in area, with bold, rocky shores, and a depth at dam
of 72 feet. We secure the above capacity by uncovering but 22 per
cent of the reservoir bottom; and, as we shall presently see, we
shall rarely need more than half this storage, and probably not
oftener than once in ten years will we expose over 10 per cent of
the area. By building side dams to keep certain flats always flowed
this may be reduced to 5 per cent; and this area will be pretty
evenly distributed around 36 miles of uninhabited shore line,
leaving the reservoir open to no valid sanitary objections. On the
contrary, by relieving the remainder of the Passaic Basin of the
flood waters of the Pompton, which now flow large areas of flat
land during wet seasons, the sanitary condition of the valley would
be much improved.
In constructing this reservoir Mr. Vermeule stated that the following
work would be necessary:
The removal of the Delaware, Lackawanna and Western Railroad from
the basin by changing the alignment for 6 miles. It may be done
without increase of length or detriment to the alignment.
Three and one-fourth miles of the Morris Canal must be rebuilt. No
engineering difficulties are involved.
Of the New York and Greenwood Lake Railway, 9 miles would have to
be rebuilt.
The New York, Susquehanna and Western Railroad would be slightly
shifted or raised for 3-3/4 miles.
A dam 2,400 feet long and 80 feet in height, with tunnels,
wasteweir, and accessory works would be required at Mountain View.
The situation is such that an ample wasteweir may be built at a
low-side dam on the solid rock of Hook Mountain remote from the
dam, and outlets may be had by tunneling the same ridge. Hence the
dam may be a plain, heavy earthen embankment; built, of course,
with every precaution but subject to less than the usual dangers of
such works. However, a masonry dam might readily be substituted.
There would be 14,000 acres of arable land, swamps, and rough
mountain land flowed.
The works are estimated to cost as follows:
Railroad and canal diversions $505,000
Dam and accessory works 1,162,000
Land damages 1,400,000
_________
Total 3,067,000
A recomputation of the drainage area above Mountain View, made by the
northern New Jersey flood commission, shows that it is 380 square miles
in extent. It was decided by this commission that the construction of
this reservoir would be the most approved method of preventing
disastrous floods in the lower valley of the Passaic. By raising a dam
to a height of 202 feet above tide, 8 inches of water on the drainage
area above might be held back, which, it was believed, would be a
sufficient maximum for flood catchment. With this amount of storage the
estimates of the flood commission showed that the remainder of the
drainage area would not turn a sufficient amount of water into the lower
valley channel to cause flood damages.
It was also demonstrated by the flood commission that by increasing the
height of the dam an opportunity would be afforded for conserving water,
and at the maximum height of 220 feet above tide sufficient storage
capacity would be available to provide 5,000 horsepower at Little Falls,
Great Falls, and Dundee dam throughout all dry seasons. The value of
such a storage reservoir for municipal water-supply purposes is
self-evident.
The cost of Mountain View reservoir would be about $3,340,000. Developed
for flood catchment with the spillway of the dam at 202 feet above sea
level the area of the reservoir would be 13.4 square miles, and the
storage capacity 7,200,000,000 cubic feet.
RAMAPO SYSTEM.
Along the Ramapo Valley there are alternative propositions, one of which
involves the construction of a dam below Darlington and another across
the head of Pompton Lake.
In either case the water might be raised to the 300-foot contour, and if
the dam across Pompton Lake were constructed a continuous lake would be
formed extending 10-1/2 miles to Hillburn, N. Y. The improvement in
either case would be positive, for as the country surrounding is hilly
or mountainous it affords excellent opportunity for the location of
summer homes and parks, the lake being a potent factor in beautifying
the situation and increasing the value of the surrounding region. There
are, nevertheless, several things to be taken into consideration, the
most important of which are the improvements which have been made by
wealthy residents along the valley where it has already been developed
as a summer resort.
By the construction of a dam at Darlington 1,100 feet long and 70 feet
high, the water would be raised to the 300-foot contour. The reservoir
would have a water area of 2,064 acres, and the approximate storage
capacity of 2,325,000,000 cubic feet.
A dam across the head of Pompton Lake 2,850 feet long and 100 feet high
would raise the surface of the proposed lake to the 300-foot contour.
This reservoir would have an area of 6.19 square miles and a capacity
of 6,300,000,000 cubic feet, equal to 17.5 inches run-off from the
drainage area. Here the measure of safety is wide, and if there were
drawn from the lake an amount of water equal to 12 inches on the
drainage area there would still be 5.5 inches which could be used for
compensating purposes.
The construction of either one of the above-described reservoirs would
involve interstate complications, as the 300-foot contour in Ramapo
Valley includes a considerable part of the State of New York. This
obstacle was deemed insurmountable by the northern New Jersey flood
commission, and that commission directed studies to a reservoir which at
the time of maximum flood would not back water into New York State to a
greater height than it already rises during such floods. The following
description is taken from the report of the engineering committee of the
flood commission:
An admirable dam site is offered on Ramapo River about 2 miles
above Oakland village. The drainage area tributary to this point is
about 140 square miles in extent, the country for the most part
being quick-spilling and upland. By constructing there a dam 700
feet long and 65 feet high a reservoir with a water surface of 2.8
square miles would be afforded, the flow-line elevation being 280
feet above tide. The capacity of such a reservoir would be
1,768,000,000 cubic feet, equal to about 5.5 inches on the drainage
area.
WANAQUE SYSTEM.
Near the headwaters of Wanaque River is Greenwood Lake, a large body of
water described in Water-Supply Paper No. 88. Its value as a flood
catchment basin is somewhat uncertain, as it is used as a storage feeder
for Morris Canal. The surface level of this lake is controlled by gates,
which naturally are operated by the canal authorities for the benefit of
the canal. Therefore it is the object to store as great a volume of
water as possible, and the water falls below the dam crest at the outlet
of the lake only when the dam opens in dry seasons and makes it
necessary. Under such conditions there is no certainty that storage
capacity will be available during the time of a great storm, and in fact
Greenwood Lake has been overflowing at the commencement of the storms
which caused both of the recent floods.
In view of the condition expressed above it will be necessary in
providing for flood catchment in the Wanaque drainage area to omit
entirely from consideration the possibility of assistance from Greenwood
Lake. Below this point in the basin are several sites at which could be
raised dams, which would effectually retain a large proportion at least
of storm run-off. They may be described as follows:
_Midvale reservoir_.--By building a dam 60 feet high and 1,200 feet long
across Wanaque River near Midvale, a reservoir would be formed which
would have a water surface of 2.1 square miles and a capacity of
1,491,000,000 cubic feet. The drainage area above this site is 83 square
miles, and the storage capacity would therefore be equal to about 7.7
inches on the drainage area. The construction of this project would
involve the relocation of about 4-1/2 miles of the New York and
Greenwood Lake Railroad; the damages apart from this would be nominal,
the cost of the entire reservoir construction being about $1,000,000.
_Ringwood reservoir_.--Ringwood Creek runs through a gorge about 1 mile
above its confluence with the Wanaque. Above this is a well-defined
basin. A dam about 70 feet high and 585 feet long would create a lake
having an area of 520 acres, the surface of which would be 380 feet
above sea level. The drainage area tributary to this point has an area
of about 20 square miles, and as the proposed reservoir would have a
capacity of 915,800,000 cubic feet, there could be conserved a run-off
of 20 inches. Allowing for a flood run-off of 12 inches there would
still be available for compensating purposes 8 inches on the basin,
equal to 373,550,000 cubic feet. The construction of this reservoir
would involve the relocation of about 2 miles of the Ringwood branch of
the New York and Greenwood Lake Railroad, and the condemnation of
comparatively valuable improvements in the proposed basin.
_West Brook reservoir_.--The drainage from 5.7 square miles might be
conserved by the erection of a dam on West Brook, a tributary of Wanaque
River, which enters it from the west. There is an available site at
which a dam 280 feet high might be erected. At this elevation the length
along the top would be about 1,150 feet and about 2,330,000,000 cubic
feet of water would be impounded. Little benefit would be derived from
such a reservoir, as the limited drainage area affords a comparatively
small proportion of flood run-off that might be well cared for at a
lower point. For compensating purposes, however, a reservoir might be
constructed here, the capacity of which could be adjusted to the actual
demands. If the dam were raised to a height of about 280 feet from the
base the storage afforded would be equal to 176 inches on the watershed,
or about four average years of precipitation, which is far beyond all
probable storage necessities. The maximum available storage capacity is
given in this case merely to show possibilities.
PEQUANAC SYSTEM.
There are few available reservoir sites of large size along the lower
reaches of Pequanac River. In the upper basin, however, there is a
sufficient available storage capacity to afford almost complete control
of destructive floods from that part of the drainage area. Large tracts
are already reserved by the city of Newark for collection of municipal
supply, and the storage capacity developed is sufficient to serve the
city throughout the driest seasons. The total capacity of Clinton,
Oakridge, and Canistear reservoirs is about 1,155,000,000 cubic feet.
These basins are not available for flood catchment, as the water is used
for city purposes and an endeavor is made to have in storage at all
times the largest possible amount. The condition is exactly similar to
that described in the case of Greenwood Lake. In considering the means
for the construction of flood-catchment reservoirs in Pequanac Basin
there must be taken into account the conservation and delivery of the
Newark supply. The adjustments with reference to the amount of water
available at Macopin intake would have to be met, and if the system were
interfered with compensation therefore would be taken into
consideration.