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emporarily improving navigation during the low-water season. 'he principal obstructions met with are the sand bars built up durng high stages, through which the river slowly cuts a channel as he flood recedes. If this process could be assisted and hastened, navigation would be improved thereby, and to this end experiments were made with dredges. These experiments, started in 1894, were successful and as a result the Commission was led to reconsider the

whole subject of the river improvement, and as a result of this

study the Commission decided to adopt a new plan for future oper973 a ations, namely, to depend for the relief of the immediate needs of

navigation upon dredging, and to restrict the improvement by bank revetment to special localities, where local interests or neces

sities demanded it. The reason for this action of the Commission, 5 may. Brex with the reports of the committees who had specially investigated fara sf the subject and the dissenting views of some members, are stated i dezand c. 3419-3423, 3430-3432, and 3439-3459. Of the above the following there are in full in the Report of the Chief of Engineers for 1896, pages

will be quoted:

"f3b* insed 2722 of eat of me pearing is of hetens ses to go back of these rry out the system of ertaken.

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One important result of experience in respect to these two kinds of channel work has been to emphasize more and more the relative importance of bank protection as compared with work for contracting the channel way by the upbuilding of new banks. It is now considered settled that in a plan for the

arted, after the lege: width the work of bank protection should precede the permeable dikes and other

structures of that class, and that the latter may be regarded as supplementary in function and as necessary only in a minority of cases.

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under way. of importance

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banks at special

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ork previously die se, and rapid chai oped the standani $ with

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If the works for bank protection originally projected had proved sufficient, as it was hoped they might, to hold the banks of the rirer with permanence, a substantial improvement of the channel throughout the worst reaches of the lower river would have been possible by this time. When they failed to realize those expectations the problem became a new one. No precedents existed to throw any certain light upon.it. It had to be taken up and worked out by original methods, experiments, and trials, As these proceeded, the necessary cost of the work increased, step by step. It was taken for granted that the disposition of Congress to undertake finally the permanent improvement of the entire river in this manner would depend in large degree upon the anticipated cost of the work, and that it was incumbent upon the Commission to find out, if it could, not only whether or no the work is possible, but the lowest cost at which it is possible. With this view the progressive changes in structure and methods which have been made have been conservative, proceeding by short steps as nece

ecessity seemed to require. A point has been reached now at which some important facts can be definitely stated. While it is not possible to say that the form of bank protection

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4.* trar nerimary to supply material for a mile of fans ****** 10+ inte in prutally five times as great as that required ts? 2

treenbuilt in the early years of the work. The çant * 2111th us in this form of mattress is so great that tbe me jest terminable along the whole length of the river from Cairs to *** Los twitt than sufficient for the making of 15 miles per size *14* y Waltat

114,16., 1kom farts together it became apparent several years ago h 18.4*, tra gradually, tam facim arcumulated and the deduction of espere

****** but it was not possible by any or all of the methods which *** to alkohol tu meruspolish much permanent improvement of the river in d}" name was nerersary to meet the urgent demands of commerce win *t, islle fillim to come, It was this disagreeable but unavoidable con Po'ste $41k these words of prerading yours, together with the recent and wondertu

*xxfotost ist of the hydraulie dredge, that led the Commission to undertake the {**$** 1,8 uf derlying the bars of the river with the view to the temporan ither dive the ist of its low water channel which has been detailed in recent ** Hapa ni? the futursson, and to which more extended reference is made else whose in this report. These experiments have proceeded favorably so far as to ble ou u washable probability of entire sucess. If it is possible in that Writy to meet the immediate necessities of commerce by securing a channel of sasinpite da potle during the low water season at reasonable cost, it is considered by the luminosius to be its first duty to advise such use of the money appropri alast by Congress as will accomplish that end with the least possible delas, With this view the commission has made no recommendation of any allotment from the appropriation for the year ending June 30, 1897, for bank protection or contraction works for the general improvement of the river except such sums to Plum Point and Lake Providence reaches as are supposed to be necessary to wake much repairs and extensions of existing works in those reaches as will

works of that Ly. - .
lly mueh superua's ***
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attress sunk and was
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river, barring error X
18, $30 per runLizz !
cost originally estinta,
rge interests depene :
ity harbors, points Tys-
tance are liable to be

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five times as great a ***
in the early years of the
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whole length of the river too
for the making of 15 Er

rly test their efficiency and permanence. And it is the general recommenda2 of the Commission now, to be followed hereafter by such special recomndations as circumstances may require, that out of the funds appropriated

Congress for the improvement of the river below Cairo such sums shall be voted to the work of dredging the low-water bars as shall be sufficient, first, thoroughly test the practicability of obtaining a good low-water channel by at means, and then, if the work shall be found to be practicable, to build, uip, and operate a plant sufficient for its secure accomplishment before any W and further revetment and contraction works for the general and permaint improvement of the channel shall be undertaken.

In considering the question of going forward now, or at a later date, with a cost not incumbet - anks and regulation of its low-water width, it is manifest from what has been

ve general and permanent improvement of the channel by protection of its e now definitely set 1% ime. It was recognized from the beginning of the Commission's work that the

aid that it must be done, if at all, upon largely revised estimates of cost and employed on a larg 28, onstruction of works of bank protection and channel contraction in detached s to supply material fuas, n unprotected bends above. In commencing work in the detached reaches of oblem presenting and beaches would be subject to influences more or less unfavorable from changes

Plum Point and Lake Providence the Commission was not oblivious of this fact, but was influenced by other considerations which seemed to overbalance this disadvantage, and it has not since seen good reason to doubt the wisdom of that decision. But the experience gained in those reaches emphasizes the fact that it is highly important in any project for general and permanent bank protection to leave no unprotected reaches above the work done from changes in which new conditions may be produced in improved parts of the river. And it is considered by the Commission that in undertaking a complete and permanent system of bank protection the work ought to begin at the upper end of the river, at or near Cairo, and be carried thence downstream with substantial continuity. The distance from Cairo to Vicksburg is 600 miles. In a project for the complete and permanent improvement of that portion of the river by the means stated some portions of it would require work on both sides of the channel, though this would not usually be the case. And it may be that in some portions of it no work would be needed at all, at least for a number of years to

As to these matters an exact judgment can not be formed in advance. But for the purpose of a preliminary estimate it is considered conservative to count on the ultimate revetment of bank line equal to two-thirds of the whole distance between the two points. Based on this assumption, and a cost of $30 per running foot, the cost of a complete revetment from Cairo to Vicksburg would be $63,000,000, and at a rate of progress of 15 miles per annum, which limit, or less, it is believed would be imposed by the available supply of material for mattress work of the construction now employed and believed to be the best, the time necessary for the completion of the work would be forty years. It is considered that the annual cost of maintenance of completed work could not be estimated at less than ten per cent of the original expenditure.

come.

became apparent several Tees -umulated and the dedor le by any or all of the r.. Prmanent improvement ? the urgent demands of ever his disagreeable but uns together with the refert at led the Commission to 2

river with the view to t hich has been detailed i ore extended reference in ve proceeded favorably se:

success. If it is possila ommerce by securing a da reasonable cost, it is consid such use of the money

with the least post
commendation of ass

e 30, 1897, for bank fact
1 of the river except
re supposed to be necess
orks in those reaches se

l'pon the general principles described the work of the Commission has since been conducted with but one slight alteration. In 1899 experiments with contraction work were again begun, this time the work being designed only for one special purpo building up sand bars and thus helping to keep the low-wate ings narrow and therefore deep. These new dikes are me tively small and light and are only adapted to special ki where it was thought they might assist the dredges, or pudera some cases render dredging unnecessary.

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The dredging operations will, for reasons stated at the best of this paper, not be discussed, but the contraction works and revetment constructed in the First and Second districts will t. described. The attempt will be made to relate the history of t works, their beginning, their development, and their suceren failures and the causes of such failures.

CONTRACTION WORKS

Of the contraction works which have been built in the Firsta Second districts nearly all have been located in Plum Point R and in preparing the history of these works, and also of the te revetment constructed in this reach, much of the compiling writing has been done by Assistant Engineer Aug. J. Nolty, has been connected with this work continuously from its incepti to the present time.

In selecting this reach of the river for the first systematie periments in regulation the Commission followed the recommen! tion of the Board of 1879, who in their report stated:

That such a trial may thoroughly test the practicability and the cost of reg lating the river and increasing its low water depths, one of the worst plati on the river should be selected. Such a place is the Plum Point Reach il: miles below Cairo). This reach is about 20 miles in length, and presents : many places excessive width, reaching two miles at high water and one and : half miles at low water. The case is made still worse by the fact that the river at one place seems to be filling up a concave bend, thus giving rise to : miles of nearly straight low-water channel, some of which is nearest the contes high-water bank.

On Plate V will be seen a map of this reach, made from the sur

vey of 1880.

For the purposes of this first scheme for river regulation this reach of the river was supposed to begin at the foot of Forked Deer Island and Chute. Here the channel of the river was near the left bank, and for the next 4 miles it hugged this, the concave, bank in what is known as Ashport Bend, the bank being a steadily caving one. At the foot of Ashport Bend or Gold Dust Landing the river

wing designed only for the

dredging unnecessary

of such failures.

CONTRACTION WORKS

-ks which have been buite I have been located in Pa -)ry of these works

, and is this reach, much of the

49 bars and thus helping teened out quite suddenly, and in the middle of this wide river therefore deep. The is located the large and high Elmot Bar. This bar was of comlight and are only adapta atively recent growth, the 1874 map (Plate IV) showing it to ght they might assist the rather low and scattered, but it has since grown in size and --rations will, for reasons o abered. To the left of the bar was what is known as Gold Dust

ght and is now as high as the main banks of the river and thickly e discussed, but the conna jute, carrying at about the bank-full stage 40 per cent of the dis-d in the First and Secon) : arge of the river, but being at low water narrow, crooked, and not ipt will be made to relax, avigable on account of snags and insufficient depth. In the mid2. their development, a: e of the lower end of Gold Dust Chute was located Island 30, one

: the older islands of the river. This divided Gold Dust Chute into vo outlets known, respectively, as Elmot Chute and the Chute of zland 30. From Gold Dust Landing the main channel of the river assed by the head of Elmot Bar over to the right bank of the river t Mill Bayou, this crossing at low water being usually shallow and lifficult of navigation. Starting at Mill Bayou the channel hugged he right, a concave, bank along what is known as Fletchers Bend, his bank being also a steadily caving one.

After following this s work continuously for 4 miles pursued a generally straight course, passing across the foot Issistant Engineer Jug, pank for some 4 miles or so, the channel forsook it, and for the next Che river for the first finally coming back again to the still concave right bank along the

of Island 30, skirting the convex left bank at Plum Point, and Commission followed to upper side of Craighead Point. This part of the river, from the in

point where it returns to this bank, was of above the average width, W-water depths, one of it, and in it were located numerous sand bars that shifted in place a place is the Plum Peir from year to year, causing a similar shifting of the low-water chanThe 20 miles in length, 2: nels that were formed through these bars. The manner in which noomiles at high water azi. these bars and channels changed from place to place can be seen by

a comparison of the maps of the reach made from time to time. (Plates LVII to LXIX.) In addition to these small and shifting sand bars there were two large and permanent ones, Osceola and

Bullerton, located close to the concave right bank. The channel bethis reach, made fine: hind them, though narrow, was fairly deep, and in some years they

formed the best, if not the only, available low-water channel in this ne for river regulatie part of the river.

The reach had for years been one of the worst parts of the river, and at low-water channel depths in the various crossings of 5 feet, and even less, had been frequently noted. Certainly a part of the river in greater need of improvement could not well be found, and it was accordingly selected for regulation.

est the practicability and >

nade still worse by the ty a concave bend, thus gira , some of which is nearest

7 at the foot of Forte

the river was near I this, the concave, hus ik being a steadily 1 Dust Landing the

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