List of civilian engineers employed on work of river and harbor improvement, third district, in charge of Capt. William T. Rossell, Corps of Engineers, from July 1, 1887, to June 30, 1888, inclusive, under the river and harbor appropriation act approved August 5, 1886.

Approximate value of plant belonging to the United States and used upon the Mississippi

River, third district.

H 1.

REPORT OF CAPTAIN W. T. ROSSELL, CORPS OF ENGINEERS, UPON THE SURVEY OF VICKSBURG HARBOR.

MEMPHIS, TENN., March 18, 1887. SIR: I have the honor to inclose herewith my report on the survey of Vicksburg Harbor.

Very respectfully, your obedient servant,

WM. T. ROSSELL,
Captain of Engineers.

REPORT.

$75,000 was appropriated for

Under the act approved August 5, 1886, the improvement of Vicksburg Harbor.

Under this clause the Mississippi River Commission directed me to make a survey of the harbor. The survey was made, extending from below Vicksburg to the upper end of Paw Paw Island. It includes Centennial Lake and the Yazoo River from near its upper mouth to where it debouches into the Mississippi River. The field work occupied the party from November 1, 1856, to the middle of January, 1887, and the maps were drawn and office work finished about March 6, 1887.

The survey consisted in:

1. A triangulation of the reach.

2. Meandering the banks and sketching the topography.

3. Locating and measuring sections on bars and in the inner harbor, where sounding was impossible.

4. Leveling all meander lines and sections not sounded.

5. Sounding on section lines throughout the entire river and Lake Centennial. 6. Obtaining direction and force of currents by floats.

The general change in the main river in this reach during the last few years has been a wearing away of the west side of Paw Paw Island, thus lengthening the bend which was shortened by the chute channel; a deposit of much of this suspended silt at the lower end of the island; a slight cave below Duckport Landing, caused by the rebound of the current from the Paw Paw Bar; a large increase in the bar in front of Nebraska Landing; a caving of the bank for about a mile opposite Nebraska Landing, and a moving and vertical increase of the bar at the mouth of the Yazoo; a caving in the bend below Nebraska Landing and the bar above Delta, a cessation of the changes heretofore taking place at King's Point, and a great increase of the bar just above; a continuation of the northward movement of the medium low-water lines of the bar closing the northwest end of Lake Centennial and all the north side of the Centennial Cut-off, and a corresponding increase in its crest; the continuation also of the heavy caving in the bend below, which threatens the stability of the Louisville, New Orleans and Texas Railroad tracks and the destruction of much of the property intervening between the present bank and the hills; a shoaling of the water in mid-stream from King's Point to West Pass, and a corresponding deepening above and below that reach.

In the inner harbor, the change has been a shoaling throughout the entire Centennial Lake, with the exception of that part adjacent to the north end of De Soto Island, which the muddy water rarely reaches with sufficient silt in suspension to cause appreciable deposit.

In the upper or southwest corner of the lake the change has been considerable, the channel from West Pass north to near De Soto Island having filled up as much as 9 feet since 1884, there now being at low water a channel in this end of the lake of but 2 feet at the shoalest crossing. Throughout the inner harbor there has been a fill (as before stated) since last February varying from 4 feet at the southeast entrance, between the point of willows and the main bank, to nothing between Ryan's Mill and the Compress, and thence no fill to the north end of the lake, except a complication

-of changes near Glass Bayou, due to its influence on the lake bottom during heavy rains, at different stages of water.

At the risk of going outside of the requirements of the resolution [directing the survey], I have decided to give my views on dredging in the harbor.

The improvement of Vicksburg Harbor, after the cut-off, was begun under a project submitted by a Board of Engineers, January 22, 1878.

The Board recommended:

1. Protection of Delta Point.

2. Construction of a bar dike.

3. Dredging cut of inner harbor.

4. Diversion into the lake of the Yazoo River, and made estimates therefor.

The protection of Delta Point has been accomplished, but, from the perishable nature of the materials (willow brush) where exposed above low water, it has required annual repairs.

Under the Mississippi River Commission dredging was done, as stated already in this report. Nothing further has been done as yet. The filling up of the arms of the lake near the river has been rapid, and a shoal has also formed near the mouth of Glass Bayou. The shoaling of the arms of the lake has been due to the sediment and other material brought in by the river while rising. The great amount of the deposit takes place where the current is checked, and the comparatively clear water reaching the back of the lake makes little or no deposit.

The amount of deposit must bear a direct ratio to the volume of water entering the lake, and if this volume be decreased so will the deposit. At present, not only does the volume of water depend on the area of the lake and the rise of the river, but there is also a current passing through the lake.

To decrease the amount of water entering, I propose to build, just below the mouth of Glass Bayou, a dam (marked proposed dam) and a dike along the ridge (marked proposed dike).

The amount of water entering here will be absolutely fixed by the volume contained in the basin. The dam should, in my opinion, be built above the high-water mark, and the dike also. The dam should be as nearly water-tight as practicable, and the dike should allow the water to pass through, but robbed of most of its silt. Undoubtedly even in this case some shoaling would take place, and periodical dredging would be needed. The amount of such sedimentary deposit can not be accurately predicted. There are similar cases now along the river in the cases of chutes closed at their upper ends. In these cases it is known that they remain open, with but little change from year to year.

The dam was also located to cut off any complications from Glass Bayou. To dredge the caual and basin will require about 1,900,000 cubic yards,

measured in situ.

The dike will cost, say.
The dam will cost, say.

Dredging will cost, say

Total......

$25,000

10,000

320,000

355,000

It is proposed to dredge both basin and canal to a depth of 5 feet below the zero of the gauge at Vicksburg, the former with a width of 300 feet, and the latter 75 feet on the bottom with side slopes of 1 to 5.

The dam is to be built of two rows of piles, 8 feet apart and filled in between with brush, longitudinal braces of wood and cross-ties of wire.

The improvement by deflecting dikes is uncertain, and although not expensive in first cost, yet when threatened cut-offs must be prevented, and when the undoubted loss of property by caving banks, where the current is thrown, is taken into consideration, the cost will be very great.

Should the Commission decide to dredge, I would recommend that the dam be built and the canal begun at the river and carried for its full width and depth as far as the money will permit. The reason for leaving the dike out for the present is that the growth of willows along the site partially does the work.

Respectfully submitted.

Colonel Q. A. GILLMORE,

Corps of Engineers, U. S. A.,

WM. T. ROSSELL,
Captain of Engineers.

President Mississippi River Commission, New York City.

APPENDIX I.

REPORT OF CAPTAIN DAN. C. KINGMAN, CORPS OF ENGINEERS, UPON OPERATIONS IN THE FOURTH DISTRICT.

UNITED STATES ENGINEER OFFICE,

New Orleans, La., June 6, 1888.

SIR: I have the honor to transmit herewith a report of operations for the fiscal year ending June 30, 1838, for the works in my charge in the fourth district of the Mississippi River.

IMPROVEMENT OF THE HARBOR OF NEW ORLEANS, LOUISIANA.

The adopted project for work in New Orleans Harbor is, first, to cover the caving bank in the Carrollton Bend for a distance of 10,000 linear feet, with a mattress of willow brush, ballasted with stone; second, to protect the portion of bank known as the Gouldsboro Bend, about 5,000 linear feet, by means of sloping submerged spurs, made mostly of brush and stone, and placed at intervals, varying from 500 to 1,600 feet. It is also proposed to protect in like manner the Gretna Bend and the great bend above Gretna.

In pursuance of this project the following work had been done up to the date of my last annual report:

A small amount of mattress had been sunk in the Carrollton Bend, and in the Gouldsboro Bend four of the six proposed submerged spurs had been completed and a fifth partly completed. Most of the material required (excepting brush and lumber) for the remaining spurs was on hand. The plant which had been changed by the substitution of three new weaving barges for the old continuous mattress plant was in laying-up quarters, and during the summer was put in order and made ready for use. In September a survey of Gouldsboro Bend was begun, to ascertain the condition of the work already done and the effect that had been produced by it. The survey showed that all of the completed spurs were in good condition, except Spur No. 6, which was some 10 or 12 feet below grade. This loss of height may have been due to compression or to the loss of some of the top cribs. It was probably due to both causes combined, for this spur as a matter of experiment was made lighter than the others, containing less brush and less stone. The result shows that the safe limit had been reached in the former spurs, and they will be regarded as a standard for similar work hereafter.

In the latter part of October work was resumed in Gouldsboro Bend and continued until February 26, on which date it was completed. Unfinished Spur No. 5 was first brought to grade by the addition of four cribs 6 feet in thickness. Spur No. 4 was then built. This is one of the largest constructed, it being over 40 feet in height, with its outer end resting in 100 feet of water. The necessary number of cribs was sunk on Spur No. 6 to restore it to grade. This completed the proposed work in this bend. No survey has yet been made to determine the effect of the finished work. Examinations made from time to time while the work was in progress showed that where the spurs were completed they held the bank between them and prevented caving. They also showed that spurs of the standard strength were sufficiently strong and durable. The spurs did not, however, cause any deposit to take place above or below them. The bottom seemed to remain about as it was at the time they were put down.

On December 14 a caving of the bank took place at a point a short distance above Spur No. 6. A survey of the locality showed that a mass of earth in the shape of a semi-ellipse in plan, and having an axis of 300 feet and a semi-axis of 60 feet had moved downward and outward into the river. Its movement was singular. It did not fall suddenly from its place, but advanced with a regular motion, so slow and so gradual that it could hardly be detected by the eye alone. Its measured rate of advance was about a half an inch a minute. Before the cave took place the slope of the bank was very steep, being 34 on 1 for the first 35 feet in depth. The earth moved was not washed away, but lies at the bottom, reducing the slope of the bank. Of course so steep a slope of earth could not be permanent, but the immediate cause of the cave was a pond of rain-water collected and held a short distauce from the crest of the bank by the railroad tracks. A few months later a similar cave occurred from the same cause in the Carrollton Bend. This cave was not near any of the protected portion of the bank.

In regard to the protection of Carrollton Bend, I would recommend that the method of protection by a continuous mattress be abandoned, and that by submerged spurs. be adopted in in its place. I think that the trial has gone far enough now to clearly indicate that the latter method is the best for this locality. It is certainly more dur