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api^ear to the writer, of a final report of a committee of this Society.

It is believed, therefore, that both the Majority and Minority
Reports should be received, the Committee discharged, and a new
committee appointed to consider again the important problems involved,
in the hope that a more comprehensive and definite report may serve
as a basis for the final action of this Society on the important problems
involved in the flood situation.



1286 DISCUSSION ON FLOODS AND FLOOD PREVENTION

Mr. E. C. La Rue* Assoc. M. Am. Soc. C. E. (by letter).— The Com-

' mittee has wisely called attention to the paucity of data available for
studies of flood control, but it does not seem consistent in the same
report to draw definite conclusions with respect to the relative merits
of the various methods of flood control and flood prevention. The
writer agrees with the statement of Mr. Knowles, on page 1230,
that the Committee has given a single view "on controversial sub-
jects on which it must be recognized that much more information
can and should be obtained".

Eor example, on page 1228, the Committee says :

"As you proceed down stream the influence of reservoirs on flood
prevention rapidly diminishes, and the influence of levees correspond-
ingly increases in importance as a method of flood protection. On
the lower alluvial reaches of long rivers, such as the Mississippi and
Colorado, they afford the only sure means of flood control."

This statement is not correct when applied to the Colorado River.
The writer has recently completed a report, entitled, "The Colorado
River and its Utilization", f in which it is shown that reservoirs may
prove an effective means of preventing floods on the lower Colorado.
The area of the Colorado River Basin is 244 000 sq. miles. The pre-
cipitation and run-off from the lower half of the basin is small com-
pared with that on the upper half. At Yuma, Ariz., 92% of the
annual run-off is contributed by that part of the drainage basin lying
above the Utah- Arizona line, which is 700 miles above Yuma. Green
and Grand Rivers, which unite to form the Colorado in southeastern
Utah, drain 70 300 sq. miles, which is only 28.8% of the Colorado
River Basin; yet these rivers contribute 76% of the water that passes
Yvmia. A dam constructed to raise the water level 270 ft., imme-
diately below the junction of Green and Grand Rivers, would create
a reservoir having a storage capacity of 8 600 000 acre-ft. On June
14th, 1914, a maximum flood of 137 000 sec-ft. occurred at Yuma.
The crest of this flood at the junction of Green and Grand Rivers
was 120 000 sec-ft., and passed that point on June 3d. By utilizing
the reservoir site at the junction of the Green and Grand, this flood
of 137 000 sec-ft. at Yuma could have been reduced to 17 000 sec-ft.
This reservoir site is 880 miles by river above Yuma, and about 1 000
miles above the mouth of the Colorado. It is clear, therefore, that
in this basin, at least, the influence of reservoirs on flood prevention
does not rapidly diminish down stream. The Colorado tends to over-
flow its banks in the vicinity of Yuma at the 25-ft. stage on the gauge.
The average carrying capacity of the channel at the 25-ft. stage is
about 50 000 sec-ft. The writer, therefore, believes that nearly all

♦ Salt Lake City, Utah.

t U. S. Geol. Survey, Water-Supply Paper 395.



DISCUSSION ON" FLOODS AND FLOOD PREVENTION 1287

overflow can be prevented on the lower Colorado, and that the flow Mr.
can be regulated to meet the demand for water for irrigation, if the ^^ ^^^'
reservoir site at the junction of Green and Grand Rivers is utilized,
and detention basins and reservoirs are constructed on the San Juan
and Gila Rivers for the purpose of reducing the violent floods that
happen occasionally on these tributaries. On the lower reaches of the
Colorado the river bed is being slowly built up, and at the present
time the river is flowing on the highest ridge of its delta. When the
flow of the Colorado is regulated, the cost of constructing levees and
bank revetments will be reduced to a minimum. It is probable,
therefore, that the final plan for the control and prevention of floods
on the Colorado will involve the construction of reservoirs, detention
basins, and levees.

As to the proper methods of controlling and preventing floods,
there are nearly as many opinions as there are engineers engaged in
the study of the problem. Each drainage basin or river system pre-
sents a different problem, and perhaps this fact accounts for the
divergence in the opinions expressed by engineers as to the effective-
ness of the respective methods of flood control and flood prevention.
The opinion of each engineer will probably be influenced largely by
conditions in drainage basins with which he is familiar.

The Committee, no doubt, did not intend its report to be inter-
preted as an invitation to engineers to discuss the relative merits of
reservoirs versus levees as a means of flood control, but the discus-
sions that have been published indicate a tendency in this direction.
To the writer it seems no more consistent for engineers to discuss
the relative merits of the various methods of flood control without
confining their discussions to conditions in a particular basin than
it would be for two engineers to debate the applicability of the Cip-
poletti weir versus the current meter as a means of measuring water,
without agreement as to the quantity of water to be measured and the
conditions controlling such measurement. One engineer, having in
mind the measurement of streams in which the maximum discharge
does not exceed 10 sec-ft., might advocate the use of the Cippoletti
weir; the other, having in mind the measurement of the flow of the
Mississippi at New Orleans, might as strongly advocate the use of
the current meter.

When adequate data are obtained, reports will be prepared present-
ing plans for the control of floods in particular drainage basins.
Discussion of such reports will be of great value, in that it will con-
centrate the attention of engineers on specific problems. With this
concentration of effort, in solving one problem at a time with but
one set of conditions, no doubt most engineers will come to agreement,
and possibly all will agree that under certain conditions a reservoir



1288 Discussio^r on floods and flood prevention

Mr. may serve more than one purpose; that in some drainage areas de-
La Rue. ^gj^tJQj^ basins will solve the problem ; that in others reservoirs must
be constructed; and that on long rivers it may be necessary to con-
struct check dams, detention basins, reservoirs, and levees.

So far as the problem of flood control and flood prevention is
concerned, it would seem that the most valuable service that can be
performed by the Engineering Profession at present is that of urging
(page 1234) the establishment of a "special agency, supported by ade-
quate appropriations, for the purpose of studying stream regulation in
its largest sense, and under whose direction all data shall be collated,
according to uniform standards and systems, so that appropriate de-
velopment of the science shall be made".
Mr. Farley Gannett,* Assoc. M. Am. Soc. C. E.f (by letter). — After

Gannett, j-g^^jij^g ^|^g report of the Special Committee on Floods and Flood
Prevention, the thought presents itself: "What is to be done next"?
It was hoped that the Committee would indicate a definite course
of procedure to be followed in order to accomplish the gradual
reduction of the flood hazard, but it seems that it has not done this.
Some members of the Society doubtless expected to find in the report
tables showing the magnitude and frequency of floods, together with
flood damage estimates, and other information, but it is thought the
Committee was wise in not publishing these data. Such data are
most useful and necessary to accomplish the control of floods, and their
wide distribution would facilitate the intelligent construction of such
works, but, without a bountiful appropriation, the Committee could
not have been expected to collect, correct, arrange, and tabulate the
vast store of records which it could have found available. A list
of references to published sources of flood information, however,
would have been a useful addition.

Flood data shoxild be collected, studied, analyzed, revised, and
made available to the Profession; and would not such work be a
proper avenue for the expenditure of the funds of the Society? Cer-
tain States are undertaking to do this; the United States Govern-
ment, in several different Bureaus, is doing some work along these
lines; individual engineers have done a great deal, but they have
not the resources in time or money to treat the data in the proper
way; and, therefore, it seems that, if this information is to be placed
at the disposal of the Profession, the American Society of Civil Engi-
neers is the proper organization to do it, even though it may cost
many thousands of dollars. It is recognized that there are other fields
which probably deserve equal attention by the Society, and that all
desirable fields cannot be covered simultaneously, but is there a
reason for doing nothing simply because all cannot be done at once?



* Harrisburg, Pa.
t Now a Member.



n- '.;-,; lii..; Hi: -/U.



DISCUSSION ON FLOODS AND FLOOD PREVENTION 1289

The Flood Committee might have been expected to publish flood Mr.
height and damage data or to recommend concurrent State and National
legislation which would tend toward reducing the flood hazard. The
latter is believed to be by far the more important. It is one thing,
however, to recommend remedial legislation and another thing to have
it adopted, and that is where the real work would come.

Channel Reduction hij Encroachments. — The writer must disagree
with the Committee in its statement that ''the obstruction of the
flood plain by the works of man has in many cases largely increased
flood heights for the same volume of discharge". In this discussion
we are dealing with great and damaging floods on large streams, and, as
a result of an intensive study of past floods and experience in passing
upon proposed encroachments in stream channels, in enforcing the
laws of the State of Pennsylvania in this respect, the writer thinks
that, except for small floods which are confined within well-defined
channels, river bank encroachments, and obstructions, have, with but
a few exceptions in Pennsylvania, had small effect on flood heights.
When floods are confined to channels between normal banks, their
height is raised by bank extensions, bridge piers, buildings, founda-
tions, etc., but great floods, in Pennsylvania at least, almost everywhere
leave the well-defined channel and inundate the whole valley from
hill to hill. During such floods, which overtop the river banks, the
extension of such banks makes little or no difference in the gauge
height attained.

With small streams the statement of the Committee applies more
truly, however, because railroad embankments, highways, etc., cross-
ing such streams over culverts of insufficient capacity, with long,
high approach fills, often retard the flow and back up the water to
damaging heights. Wlien such accumulations of water finally overtop
the embankments and cut them away, the damage and stage below
are often far increased.

On Mill Creek, at Erie, Pa., with a tributary water-shed of 13
sq. miles, $2 000 000 damage was done by a flood on August 3d, 1915.
This was the third great flood during the last 40 years, each doing
vastly more damage than the one previous, not so much because there
was more water, but because each time there was vastly more prop-
erty, in houses, stores, and factories, to be damaged, and also because
inadequate culverts carrying streets over the creek, with approach
fills, became clogged, backed up the water, were overtopped, and the
approaches cut away, to disgorge the accumulated water down to
the next culvert, where the process was repeated.

One of the greatest obstructions which can be placed in a big
river, as far as impeding the area is concerned, is a masonry arch
bridge. Yet when the Cumberland Valley Railroad Company asked



1290 DISCUSSION ON FLOODS AND FLOOD PHEVENTION

Mr. permission to place such a structure nearly a mile long over the
Gannett, g^squehanna River at Harrisburg, it was found that its effect on
an estimated maximum flood of 900 000 sec-ft. (previous actual maxi-
mum flood 700 000 sec-ft.) would be to raise it 0.9 ft. over what it
would be without a bridge.

Encroachments, however, are going on in every place where no
control over them is being exercised; and, if permitted to continue,
will in time become of consequence. Heretofore, except at a certain
limited number of places (considering only large streams), they have
not become of damaging dimensions, but, as every little bit tends
in the wrong direction, all encroachments which would tend to restrict
flood discharge below safe limits should be prohibited. Few States
have legislation on this subject. Until recently, the National law
regarding the building of structures in navigable rivers was not
enforced from this point of view. The length of rivers classed as
navigable is so great, and the corps of engineers available to the War
Department to enforce this law is so small, that an attempt to carry
out its provisions is only made at certain points.

Pennsylvania has had a good law, well enforced, for 9 years, con-
trolling encroachments along, or obstructions in, stream channels,
and a vast benefit has resulted, not so much in bettering previously
existing conditions as in preventing worse conditions from arising;
and improvements over previous conditions have been obtained at
many points. This law prevents the dumping of wastes of all kinds
over river banks, unless the slopes are protected, and thus tends to
reduce silt carriage by the streams, to be deposited lower down. None
of the neighboring States has such laws, and there is nothing to
protect Pennsylvania from receiving in its rivers the washings of
refuse from banks in States up stream.

Such a law, enacted by all States, modified as necessary to meet
local conditions, is a prime requisite and a most proper recom-
mendation for the Flood Committee to make, in order to preserve the
streams as they are, prevent them from getting worse, as far as channel
capacity is concerned, and to effect a measure of improvement when-
ever opportunity offers.

The Popular Fear of Dams. — Another thing which the Society can
do to further flood control is to assist in disabusing the public mind
of the idea that a dam is a dangerous structure. As a result of
several disastrous dam failures, two of them in Pennsylvania, the
public has the idea that a dam is bound to be a grave source of
danger, and the location of such a structure above a city a menace.
The broadest schemes of flood control cannot be developed unless
this feeling is removed, and it can only be removed by a concerted
campaign of publicity such as could and should be carried on by
. the American Society of Civil Engineers.



DISCUSSION ON FLOODS AND FLOOD PREVENTION 1291

Surveys and estimates at Erie showed that the most satisfactory Mr.
as well as the most economical method of controlling floods in Mill *^^"°®"-
Creek was by the construction of a detention reservoir and a conduit
18 ft. wide; but, on account of the feeling in Erie against a dam of
any kind, and of the necessity of going before the people with a
bond issue election for funds with which to construct the flood
control works, it was decided to adopt an alternative plan of a
much larger conduit and omit the dam entirely, at an added cost of
more than $100 000. It was believed by the City Commission that
if a plan involving a dam was submitted to the voters the bond
issue would fail. Without the dam, the bond issue of $950 000
carried by a five to one vote. The City Commission of five members
was unanimously in favor of the plan involving a dam, as opportunity
was afforded to convince them of its advantages by frequent discus-
sions ; but such methods could not be applied to the entire population
in the short time available. Therefore the furtherance of a propaganda
favorable to dams, and the spreading of the conviction that dams
are not dangerous, would be an important function which the Society
could assume in furthering flood control.

Multiple Use of Reservoirs. — The writer believes, with Gen. Chit-
tenden, that reservoirs may be utilized satisfactorily for flood control
and other purposes as well. He had occasion to work out this prob-
lem on two large storage projects, and in one of these cases it was
thoroughly proved that a reservoir, designed primarily for increasing
the dry-weather flow for industrial use, would reduce floods in the
congested section of the river below, by 30% in height, and would
practically eliminate damage. In the other, by raising a proposed
masonry dam for water power a very few feet, almost complete
control of floods on a water-shed of 1 200 sq. miles, would be effected.
In the former case, the reservoir is long, wide, and shallow, covering
30 sq. miles, on a water-shed of 150 sq. miles. The absorption of
flood flow by this reservoir would be enormous, a 3-ft. rise absorbing
an 8-in. rainfall on the water-shed. The freeboard on the dam is
10 ft. In the latter case, the dam is about 260 ft. high, and the
reservoir more than 40 miles long. The capacity curve of this
reservoir is such that a few feet on top gives capacity equal to a
large percentage of the volume below the level required for water
power.

With few exceptions, storage in the upper part of a reservoir is
the cheapest, so that, by increasing the height of dams erected for
other purposes to a height greater than necessary for that primary
purpose, the necessary storage for flood absorption will be obtained
at more reasonable cost than if a dam or reservoir is built only for
flood control.



1392 DISCUSSION ON FLOODS AND FLOOD PEEVENTION

Mr. Several of the European nations have in this way created effective

' control and utilization of important streams. Thus, storage devel-
opments on the Oder River, in Silesia, has effected flood protection
in the valley below and has also permitted the generation of several
thousand horse-power; storage for navigation improvements on the
River Rhone has reduced flood heights below storage reservoirs con-
structed with both ends in view.

Floods come so seldom, strike at such widely different parts of the
land, and at such varied seasons, that in the popular mind they have
come to be accepted as acts of Providence. This superstition is being
gradually eliminated, but the feeling is still prevalent that floods,
like lightning, never strike twice in the same place, and so there
is no use trying to do anything about it. Furthermore, the writer
thinks most engineers will agree that it is impossible to construct
flood control measures, where a likelihood exists, if a damaging flood
has not occurred, that the financial and governing bodies will refuse
to "lock the barn door before the horse is stolen," even though one
can show the presence of thieves in the vicinity and the absence
of locks on the doors. Flood protection or control measures are
usually very costly, and floods seldom recur in any one place, and
it is impossible to prophesy how soon the next one will come, so
that it is impossible to determine exactly the amount of money
which can be expended economically for such works. Again, it is
usually necessary in large flood control projects to obtain the co-opera-
tion of corporations, cities, counties. States, and the Federal Govern-
ment, or several of them. All these conditions, as well as numerous
others, make the final accomplishment of water storage measures, for
flood control alone, a long and laborious undertaking, so long that
often the necessity therefor and the losses and horrors of the last
flood have been measurably forgotten before all these steps can be
accomplished, and the project fails.

For these reasons the writer believes that real widespread flood
control through reservoir construction and storage will be brought
about by the construction of reservoirs principally for other utiliza-
tion purposes, such as water supply, water power, industrial use,
navigation, irrigation, and for esthetic purposes, such as park lakes,
improvement, sanitation, etc.

Our existing State laws, under which most works of this kind
would be and are built, will have to be amended in most States to
provide a means by which such multiple use may be made of reser-
voirs through the division of cost between, for example, a corporation
building a water-power reservoir and a city desiring flood control, or
between one city desiring water supply and another requiring flood
control, etc.



DISCUSSION ON FLOODS AND FLOOD PREVENTION 1293

Such legislation has been suggested for Pennsylvania, but has Mr.
not yet been placed on the statute books. Projects involving several
hundred thousand continuous horse-power are now chartered by this
State, bvit remain unbuilt, because of the lack of definite and favor-
able water-power laws under which they may be built and operated.
Others are too costly, as water-power projects alone, to warrant con-
struction in this State, the home of coal. With favorable water-power
laws, and with the right to co-operate with municipalities, counties,
and the State, many hundreds of thousands of horse-power, now
going to waste, would be developed; many towns and cities would
have reduced flood hazards, navigation on several large rivers would
be improved, and sanitary conditions along the water-fronts of many
river communities would be greatly benefited.

Thus another line of legislative enactment, essential to the pro-
mulgation of flood control, is the passage of laws permitting and
facilitating the generous development of water supply, water power,
and irrigation projects, and the division of the cost of constructing
and operating them between corporations desiring such works for
financial return, and municipalities, counties. States, and the Federal
Government desiring them for flood control and navigation.

The Water Supply Commission of Pennsylvania approved of the
incorporation of a large water-power project in the western part of
the State, involving the construction of large storage reservoirs and
the installation of 200 000 h. p., on condition that the operation of
the main storage reservoir be subject to the direction of the Com-
mission, as respects maintaining a certain dry-weather flow below
it, and as respects absorbing floods.

Forests. — The writer thoroughly agrees with Gen. Chittenden in
his contention that, though forests may and probably do mitigate
ordinary floods to a certain extent, they do not affect the volume of
discharge in great floods. Anything but circumstantial and theoreti-
cal evidence on this point is impossible to obtain. The studies which
were made of Pennsylvania river floods showed that whenever we
coiild go back 75 or 100 years, substantial and reliable records of
floods were often found exceeding anything in more recent years,
since the forests were largely removed. This was clearly shown by
finding accurate records of two floods at Pittsburgh, in 1762 and
1763, considerably exceeding that of 1907. Also by finding records
of a flood on the Susquehanna River at Wilkes-Barre, in 1865,
exceeding that of 1902 by several feet in height, and floods in 1784
and 1807 nearly as great. A flood in the Schuylkill River in 1850
exceeded that of 1902 materially. These facts prove nothing, but
they show that the dense forest growth, which covered the State at
the earlier dates, did not prevent great floods, which, if they occurred
to-day, would be truly disastrous.



1294 DISCUSSION ON FLOODS AND FLOOD PREVENTION

Mr. Detention Reservoirs. — The writer cannot but feel that on large

■ streams, where water power might be obtained, or where navigation
improvement might be gained by storage, detention reservoirs are an
economic waste. It is unfortunate that the greatest and most spec-
tacular flood control project of our time, the Dayton project, is
planned on that principle. The conditions there apparently made
that the only plan that could be adopted, just as at Erie, conditions
made the plan without a dam the only one that could be put through.
The Erie case also is unfortunate, but being smaller, the failure to
utilize the best and most economical method is not so harmful, as



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