have been at a moderate stage,* may be placed at its mean of 31 000.
Deduct 20 000 for the crevasse at Austin, and we will have 1 586 000
for the maximum discharge at Helena, and it is probably well within
tlie truth. From the extreme rapidity with which it was poured down,
and the still more rajiid recession of the flood, it is probable that the
reservoir rather increased the discharge than diminished it.

By examining carefully the rei^orts of the measurements of the water-
escape over the St. Francis Front in 1882 and 1883,1 we may form a pretty
correct idea of the movement of the waters both of the river and of the
swamp. In both these years, we perceive a great flow from the river
into the reservoir between New Madrid and Memphis, the latter place
being regarded as about on the dividing line between inflow and out-
flow. The observations of 1883 are esijecially valuable, as they began
at the time of high water at Cairo and accompanied the flood down the
river, terminating with the exact time of high water, or the swell from
the return flow, at Helena. In 1883, then, it ajjpears that from Memphis
to a mile or two above the mouth of the St. Francis Eiver, the main
stream and the reservoir formed, in effect, one continuous sheet of
water, there being no return flow of any consequence, as is evident
from the fact that at St. Francis Island there had been returned only
some 32 000 feet of discharge since leaving Memphis. "Vast quantities of
water escaped over the banks in bends, only to return over the point
into the bend below. By the time the vicinity of the St. Francis is
reached, the basin is extremely narrow — only five or six miles wide — and
the water is impounded there. As the river falls, the reservoir begins
to emi^ty itself higher up, and in 1882 (the examination being made a
week after the maximum stage) there was found to be a considerable
escape all the way from Memphis down.

It is not easy to reason satisfactorily from 1882 to 1886, as the cir-
cumstances of the two years were not at all similar. Between 1883 and
1886 the comparison is closer. We may reason, therefore, from 1882 to
1883, and from 1883 to 1886.

The great increase of discharge in the last foot and a half at Helena
in 1882 X (about 300 000 feet) was due to the steepness of the sloj^e.

* The Wittsburg gauge was very high, but it cannot be depended on, as it was affected
by the overflow water. White River, which runs parallel to the St. Francis, and is affected
by similar cunditions, stood on the 27th ot April at 16 feet at Jacksonport.

t Report of the Mississippi River Commission for 1884.

t Report of Mississippi River Commission for 18S3, and see the discharge curve as
plotted in the plates accompanying that report.



214 STARLING ON MISSISSIPPI FLOOD HEIGHTS.

This is not fairly represented bj the slope Helena-Malone's, which was
0.43. The slope Helena-Delta (8 miles below) was 0.60, and Helena-
Friar's Point (13 miles below) 0.53. On the other hand, the slojie Trot-
ter's Lauding (3 miles above)-H3leaa was only 0.42. The mean slope
Trotter's-Friar's Point was 0.51.*

These irregularities are i^artly due to several crevasses in the vicinity
of Helena, and in the immediate neighborhood of the places just men-
tioned. Partly also they are due to the stage and the circumstances.

In 1886 these gaps had been closed, and the slope Helena-Friar's
Point was 0.48 instead of 0.53. On the other hand, the slope Trotter's-
Helena was steepened to 0.73. From Trotter's to Friar's Point the slope
was a trifle steeper than in 1882, being 0.52.t Above Trotter's, 1886 was
higher than 1882, in a diminishing ratio as we ascend, until Austin is
reached, after which it is lower. These circumstances would seem to
indicate that the engorgement began higher up in 1882, that its wava
was flatter, its crest lower down and of less altitude. These circum-
stances partially offset one another so that on the whole, even with a
greater depth in 1886, and a greater mean slope, the velocity may have
been little more than in 1882. The additional 0.9 foot, then, of gauge-
height would not give a proportionate increase of discharge, and per-
haps 1 600 000 would cover it.

The flood-line of 1883, from Memphis down, was almost i^arallel ta
that of 1882, and a trifle lower. The situation at Helena was very similar
in every respect, and the discharge of the two years must have been
nearly the same, 1883 being a little less.

Ther^ is a considerable resemblance between 1883 and 1886, as far
down as Austin, the high-water marks of the two, where they can be
compared, being usually very close together — the greater volume of the
former being offset by the escape into the Yazoo Bottom, which from
Memphis to Austin was, in 1883, estimated at 125 000. la 1886 it Avas
perhaps 20 000 — from a crevasse at Austin. There probably reached
Austin, in 1883, about 1 675 000 feet of discharge— and not miich less
in 1886. This may serve for a rough check on the comi:)utations just
made. From Austin down 1886 gained rapidly on 1883, owing to the
closure of the numerous l)reaks in the Mississippi levees, whereby some
166 000 feet were added to the discharge.

* High water observations of 1882, lu Report of Mississippi River Commissioa for 1885.
t High water observations of 1886, in Report of Mississippi River Commission for 1837.



STARLING OX MISSISSIPPI FLOOD HEIGHTS. 215

The reason that so much importance is attached to the discharge of
1886, is that it occurred substantially under the conditions that must
prevail in the future. The White River Basin can be closed only for a
limited distance, and whatever may be done there hereafter cannot
greatly affect the result. If it could be known with exactitude how
much water passed Helena at the height of the flood of that year, we
could reason with considerable accuracy as to results to be reached in
the river below. It is thought it may be assumed, keeping Avithin the
figures, at 1 600 000. Very possibly it was 1 650 000 or more.

What may now be ex^jected to hapjDen when 200 000 feet are added
to this ? In 1882 such an increment raised the gauge only one foot,
under the steep and constantly increasing slope jast mentioned. Is this
IDhenomenon likely to be repeated in the future ?

In the first i^lace, what was the effect of the crevasses above and
below Helena, in 1882, on the slope, velocity and gauge-height ? There
were a series of crevasses in the neighborhood of Trotter's Landing, 3 to
10 miles above Helena, discharging about 150 000 feet, and three or four
nearly opposite, discharging 21 080. There was a break just below
Helena, on the White Eiver Front, with a dischai'ge of 63 000, and
one a mile and a half above Delta, or 6.5 below Helena, with a
discharge of 40 650, besides numerous smaller gaps, the most notable
of which was six miles below Friar's Point, with a discharge of 28 000.
Total from Helena to nineteen miles below, 181 700.*

Observation shows that a crevasse dej^resses the flood-line in its imme-
diate vicinity, and to some extent both above and below — the jirincipal
part of the effect being local and at the crevasse itself; that is, there is a
holloAv in the high-water profile at that point, the slope being steepened
above and flattened below. A crevasse above a given jjoint diminishes
the discharge at that point by the amount withdrawn, diminishes the
velocity, and for that reason does not proportionally lessen the flood
height. A crevasse below a given point increases the velocity and
diminishes the flood height at that point. The diminution of flood
height can never be equal to that which takes place at the crevasse itself.
Li^t A Che the slope of a confined stream. Let a breach be made in the
levee at B, depressing the flood-line at that point by one foot. This
steejjens the slope, increases the velocity and lowers the flood-line at ^4.

* Crevasse Observations of 1882, in Report of the Mississippi River Commission for 1884.



216 STARLING ON MISSISSIPPI FLOOD HEIGHTS.

It cannot, however, lower it by so much as one foot. If it did, it would
restore the slope to^vhat it Avas, and the reduced gauge-height would not




be sufficient to pass the discharge. Moreover, in that case, the flatter
slope from B io G would cause a " backing up " of the water at B and

from there to A.

Now ia 1882, had there been no breaks, the slope Helena-Friar's
Point could not have been less than in 1886, namely, 0.48.* The dif-
ference between this and the actual slopes (0.60 to Delta, 0.53 to Friar's
Point) shows the maximum possible depression caused by the breaks of
1882, L e., 0.96 at Delta and 0.65 at Friar's Point. Therefore, had there
even'been no compensating influeace in the shape of the breaks above,
the water-line at Helena could not have been lowered by so much as one
foot by the breaks below, and consequently a fraction of a foot more at
Helena, had the levees been intact, would have carried all the discharge
that passed there in the channel.

The great increase of velocity in 1882 which occurred at the height
of the flood, and upon which so much stress is laid, could not have been
materially assisted by the breaks at Helena and Delta. Those breaks
had been discharging a long time when the great increase of slope
occurred Now the rise at Helena could not possibly have increased the
discharge through the breaks by more than 20 000 feet-whereas, the
increase of the discharge at Helena was 300 000. The st eepening of

:^t bT^bVected that"^^8^^h^a7greaterdisclnrge than 18S2, and that the slope assumed
i« too tlep It S answered that iu 188T. .ith a discharge confessedly less (^^ ^ «° ^ -^^
and a gauge-height O.ir less than in 1382. and without a crevasse anywhere, the slope Helena-
Friar's Point was ll.



STAKLTNG ON MISSISSIPPI FLCOD IIIIGETS. 217

the slope was therefore not due to the crevasses below, ard would uot
have been, had there been none above to compensate them.

As things actually were, the great breaks above and below produced
oi^posite effects and offset one another, so that the slope was not essen-
tially altered.

There is no reason, therefore, why the experience of 1882 should not
be repeated. The very nature of an engorgement arising from the cause
supposed — that is, from a sudden influx of dead water— necessarily implies
a steepening greater than the ordinary, followed by a "flattening out."
Had the flood gone still higher, there is no reason to doubt that the
slope and the velocity would have gone on increasing. Tlie same reasons
which availed to increase the slope to 0.51 would have brought it to 0.60
or so, which is about what would be required to pass 1 800 000 feet at
an additional elevation of one foot. The velocity required would be
7.55.

In the meantime the regimen of the river has undergone a change.
The channel from Trotter's to Friar's Point has suffered the natural
consequence of the immense losses of water which it experienced, and a
manifest deterioration has taken lilace. * This process has already been
alluded to. Many years ago, it was explained with great force and
clearness by Major Barnard,! ^^"i^o remarked that a very short time w'as
required for its operation to become manifest. "One season of high
water," says he, "is suflicieut to complete the change; the succeeding
rise in the river being governed by the new order of things." By so
much the more should a marked silting up of the channel follow three
such extraordinary floods as those of 1882, 1883 and 1881.

Accordingly, in 1886, with a discharge perhaps not much more than
in 1882, the river was 1.47 higher at Trotter's, 0.9 higher at Helena and
1.38 higher at Friar's Point. Therefore the flood-line has probably been
raised materially. Were the discharge of that year known with precis-
ion, we should have an accurate measure of this rise.

The violent change brought about by the sudden rebuilding of the
Mississippi levees has now done its worst. The new regimen of the river
has been established. Should another 1882 come, it will find the situa-
tion the same as before, except for the elevation of the flood-line perhaps

*rhis is the opinion of Major Dabney, Cliief Engineer of the Yazoo-Mississippi Levee
District. See his Report of August 21st, 1888.

tin his well known letter to Mr. G. W. R. Bay ley, printed at Baton Rouge in 1860.



218 STARLING ON MISSISSIPPI FLOOD HEIGHTS.

the greater j^art of a foot.* The recurrence of the same conditions will
bring about substantially the same results. The conclusion I draw is
that the experience of 1882 is a safe precedent for the future ; and that
one foot above 1886, or a gauge-height of 49.1, is likely to be sufficient to
carry ofif a discharge of 1 800 000 feet. It must not l)e forgotten, how-
ever, that at the turning jjoint of a flood, the velocity is sometimes
slackened a little,! and a margin of safety of a foot might be required,
so far as Helena itself is concerned.

In considering the reach from Helena to Arkansas City, the experi-
ence of 1886 will not be a safe guide. It is true that the two or three
breaks in the upper Levee Districtof Mississippi were insignificant — but
there were considerable gaps in the levee at the foot of the White River
Basin, which divides that area from the Tensas Basin. In 1887, how-
ever, this line was held, as well as all the Mississijipi levees. Moreover,
the high water discharge was measured at Arkansas City. Therefore,
we shall have to rely mainly upon what we can learn from this flood and
that of 1888.

The flood of 1887 did not reach so great a height as 1886 at Cairo, New
Madrid, Helena or Arkansas City, but it was in total volume greater
than 1886, and accordingly produced a more considerable effect in the
lower part of the Mississippi Valley. It is too often forgotten that an
extreme gauge-height at the head of an alliivial valley is not at all an
exact criterion of the magnitude of a flood lower down. A high and short
wave, when "flattened out," may be of less significance than a long one
of less height. Duration of a flood, therefore, is of fully as great con-
sequence, as regards gauge-heights below, as elevation— and the maxi-
mum discharge at Cairo or Columbus does not aftbrd any certain indica-
tion of the height to be reached at Vicksburg or Red River.

The discharge of 1887 at Arkansas City, as measured, varied from
1 417 408 to 1 491 735, with a probable value of about 1 440 000 and a
probable velocity of 6.15.:|: With the "White and Arkansas Rivers at low
stages, this should indicate a discharge at Helena of about 1 390 000 and
a velocity of about 6.00. The same conclusion is reached from the

* Of course on the supposition that the assumed discharge of 1 600 000 is correct. It may
have been more. It can hardly have been less. In either case, the roasjuiug is not aflfected,
except (luantitatively.

t See Humphreys and Abbot, page 315, the Helena observations of 188-2, and the Columbus
observations of the same year. In Report of the Mississippi River Commission for 1883.

t Report of the Chief of Engineers for 1887, page 2888.



STABLING ON MISSISSIPPI FLOOD HEIGHTS. 219

gauge-heights and slopes at Columbus and Helena. The stage at the
latter point was 46.3.

The high water of 1888 hardly deserved the name of a flood at
Helena. It was measured at Wilson's Point, with a discharge of about
1 200 000.* White Kiver and the Ai'kansas were at a medium stage,
and contributed probably about 80 000 feet, so that it is probable that
not more than 1 120000 passed Helena, at a stage of 42.8. The stage at
Arkansas City was 45.2.

Captain Rossellf has made a careful tabulation of the movements of
the Cairo, Helena and Arkansas City gauges for the different wave crests
from 1880 to 1886 inclusive. From these tables it appears that the Arkan-
sas City gauge is almost uniformly the higher. For gauge-heights from
30 to 40 feet the mean superiority is 0.82 feet. For heights over 40 it is
about 1.2. From this estimate are excluded such observations as were
taken when the levees were broken and the river out of its banks during
the great flood-years. Such data are evidently of little value. They
would reduce the above average to about 0.10. The only high- water
observation that is available is that of 1887. In this year the Helena
gauge stood at 46.3, the Arkansas City gauge at 46.85. :{: Fortunately,
too, the Arkansas and White Rivers were both low. Probably their joint
discharge did not exceed 50 000 feet.

Generally the difference between the two gauges is fairly attributable
to the discharge of the tributaries; or rather this over-compensates the
difference; that is, an equal stage at the lower station is sufficient to
carry off not only the discharge at Helena, but also a portion of the
increment received. According to the observations of 1884-85, the dif-
ference in discharge in favor of Arkansas City varies from 25 000 to
100000 feet. We may therefore adopt the least favorable assumption
that the reading of 46.3 on the Helena gauge represented an erjual dis-
charge at the same stage at Arkansas City.

If no tributaries intervened, and the river were confined between
levees all the way from Helena to Arkansas City, then the high-water
gauge-height at the latter place could never equal that at the former.

* MS. communication of Captain W. T. Rossell, Corps of Engineers, U. S. A., and Arthur
Hider, Esq., M. Am. See. C. E., United States Assistant Engineer.

t In an imprinted paper laid before tlie members of the Mississippi River Commission
in 1888.

t There is a little discrepancy here. This is the official record; but the reading reported
by Mr. Childs, who took the discharge measurements, was 46.63. See report of Chief of
Engineers for 18S7, page 2888.



220 STARLING ON MISSISSIPPI FLOOD HEIGHTS.

After the mean high-water slope has been attained, at which the velocity
is constant at all stations, then any addition from above must result in
an acceleration of that velocity; therefore the cross-section below will
not increase in proportion to that above, and the greater the flood, the
more striking will be the disproportion. How great this may be we
have no means of knowing. We must content ourselves with the con-
viction above expressed. If, therefore, the flood-plane be assumed as
equal in elevation to the mean (it is really above it), then an addition to
that elevation of, say, 2.7 feet at Helena could never result in as great an
elevation at Arkansas City, under the circumstances supposed ; and the
gauge-height at the latter place could never equal the assumed max-
imum of 49 feet. If the velocity of 7.55 at Helena be maintained at
Arkansas City, it will pass the discharge of 1 800 000 at a height of
48.16. It is not asserted that the velocity will never be diminished. It
will be subject to local variations, from diff'erence in conformation and
dimensions of cross-section, from the effect of bends, shoals, islands,
etc. It is probable also that the descent down a very steep slope, aa
below Helena, where there are no bends to check the acceleration, will
result in an impingement against the bottom, a scour and a flattened
slope beyond. All these variations, however, will be self-compensating-
— will be merely oscillations, in fact — and as a whole the velocity should
increase, when above mean flood-line, until a change of slope occurs
from a fall above.

This reasoning cannot be verified, at this time, by testimony derived
from facts, because the distance from Helena to Arkansas City is so
great (132 miles) and the relations between them so changed by the
interijosition of the tributaries that a comparison between their daily
gauge records is fruitless.

What will be now the disturbance produced by the White River
Basin and the tributaries ? As to the former, it is thought, as already
intimated, that its effect cannot be very great; and in assuming the flood-
line of 1887 as the standard, we have includetl the modifying etlect of
the reservoir, whatever it may be. The maximum discharge of the trib-
utaries I suppose to be about 300 000 feet.* We have a rough way of
getting at the effect of this discharge on the flood-line at Arkansas City
from the records of 1885. There were gi*eat freshets in the White and

• See Plate III of Colonel Suter's ixiper on the luvestigatiou of Discbarge Measurements;
Mississippi Kiver Commissiou print, 1888.



STARLING ON MISSISSIPPI FLOOD HEIGHTS. 221

Arkansas Rivers in l)otli January an;! April-May of that year. The
latter fortunately coincided almost precisely with the citlmination of the
rise in the MississiiJjji, so that by comparing the height of the wave-
crests at Helena and Arkansas City (knowing approximately the ordi-
nary relation which subsists between those gauges, suj^posed to be that
of equality), it is easy to see what was the effect of the increment from
the tributaries. The gauge-reading at Helena on May 4th was 38.75.
At Arkansas City on May 8th it was 42.60. Therefore the rise due to the
discharge of the tributaries, which were nearly at their maximum flood
height, was 3.85 feet. The discharge at Helena I suppose to have been
about 920 000 feet, and the velocity about 4.7. At Arkansas City, after
the increment, it was probably about 5.4.* Xow the effect of a given
increment ui^on the height of a flood should be inversely as its velocity.
If the velocity before the increment be 7.55, the increase of height at
Arkansas City will be 2.33, and the gauge-reading 50.49. The velocity
at Arkansas City will be 8.52.

These velocities seem very great, yet they are not entirely beyond
exami^le. At Columbus, in 1882, the velocity is thought to have reached
8.3, and in 1858, if the reductions of Humphieys and Abbot maybe
depended upon, a velocity of 8.47 was attained. We must remember
that we are treating of unexampled matters. Man has never seen such
a discharge as 2 100 000 feet in one channel, and when he does see it, it
will be accompanied by equally extraordinary attributes.

We cannot receive the evidence of the high-water discharges at
Arkansas City, especially that of 1887, in support of any estimate to be
made for the futui'e, for the reason that we cannot expect the circum-
stances under which it was made to be repeated. The slope Helena-
Arkansas City of that year will indeed occur again, and i^robably even a
steejier — but the slope Arkansas City-Greenville in 1887 was 0.35, and it
is not likely that this will be i^aralleled, still less exceeded. It is not
necessary that it should be— for Arkansas City is only to a limited
extent an origin of velocities; on the contrary, it is believed that the
river will reach there with a velocity already sufficient for its purpose.
We may rely upon the long fall, at extreme flood height, with a steep
slope, from Helena, and upon the volume, already beyond any jirevious

* Unfortunately the discharge measurements at Helena and Arkansas City in 1884-85
were discontinued just before this time. I can only infer from parity of stage in the Jan-
uary rise.



222 STARLING ON MISSISSIPl'I FLOOD HEIGHTS.

example at Helena, and now furtlier augmented, it may be, at the
mouth of White Elver. If a discharge of perhaps 1 150 000 in 1885
increased its velocity from 4.7 to 5.4, it will not be more difficult for a
discharge of 2 100 000 to increase from 7.55 to 8.5.

In considering the reach from Arkansas City to Vicksburg, it will l^e
possible to bring the reasoning hitherto employed to the test of fact
— there being two important circumstances to guide us. First we
have had the invaluable experience of a perfectly confined river, up to
extreme high-water mark throughout a great part of the reach; and
secondly, we have stations so near together that. their slope may be
compared day by day, and where daily records have been kejjt for
several years.

The year alluded to was 1888. As has been already remarked, above
this reach the river was only moderately high. At Arkansas City the
gauge stood at 45.2 — being 1.8 below high-water mark ; at Greenville it
was 1.2 below, at Longwood up to high-water mark — which elevation
was maintained about to Mayersville. At Lake Providence the gauge
was 0.22 below high-water mark, the disparity increasing thence to
Vicksburg, where it stood at 44.2 on the gauge — 4.G below 1882, or 4.8
below 1884. .

There is no difficulty in understanding this condition. For the last
twenty-five years the water has had free escape over the right bank
(the front ©f the Tensas Basin), and had accommodated itself to this
order of things. Consequently the bottom of the bed has been actually