In compliance with the resolution of the Senate of the 17th instant, a report from the Chief of Engineers upon the survey of the Mississippi River near Vicksburg. MARCH 31, 1871.-Ordered to lie on the table and be printed. To the Senate of the United States : In answer to your resolution of the 17th instant, requesting, "if not incompatible with the public service, the report recently made of a board of officers of the Engineer Department on the condition of the Mississippi River near Vicksburg, Mississippi, with such remarks, suggestions, or recommendations as may be made by the Chief Engineer of the Army," I herewith transmit a report dated 28th instant, with accompanying papers, received from the Secretary of War. EXECUTIVE MANSION, March 31, 1871. U. S. GRANT. WAR DEPARTMENT, The Secretary of War has the honor to return to the President of the United States the resolution of the Senate of March 17, 1871, and to submit the accompanying report and communication from the Chief of Engineers upon the examination and survey of the Mississippi River near Vicksburg, Mississippi. WM. W. BELKNAP, OFFICE OF THE CHIEF OF ENGINEERS, SIR: I have the honor to transmit, in compliance with the resolution of the Senate of the 17th instant, a copy of a communication from Lieutenant Colonel W. F. Raynolds, Corps of Engineers, of February 8, 1871, inclosing a report upon the examination and survey of the Mississippi River near Vicksburg. In my letter of the 2d instant, transmitting the same communication, which was subsequently sent to the House of Representatives, I expressed a concurrence generally in the views contained therein. Were the amount of the estimate available, possibly the work of protection proposed might be completed. One of the effects of the cutoff will be to transfer the city landing two or three miles below its present position, and to a locality where the form of the river bed will not be as favorable for such uses as at present. The evil threatened is one of great magnitude to the city of Vicksburg. Very respectfully, your obedient servant, A. A. HUMPHREYS, Brigadier General and Chief of Engineers. Hon. WM. W. BELKNAP, OFFICE OF WESTERN RIVER IMPROVEMENTS, St. Louis, February 8, 1871. GENERAL: I have the honor to submit herewith the report of Captain C. R. Suter, Corps of Engineers, upon his examination of Vicksburg Harbor, made under my direction. The report, with the accompanying maps, sketches, profiles, &c., gives a clear conception of the condition of affairs at that place, and makes it evident that the apprehensions that the river will seek a new chaunel, leaving Vicksburg an inland town, are only too well founded, and the necessity for prompt energetic action to prevent such a calamity is manifested, if, indeed, the time for action has not already passed. There can be no doubt that the remedy proposed would effect the object in view if it could be promptly applied, and I see no more economical way of securing the result, or any which could be more speedily carried out. Still I doubt if the work can be done in time to prevent the impending calamity. Hence it is proposed to attempt to save the harbor of Vicksburg; it is of the greatest importance to commence at once. By doing so, and beginning the revetment at the upper portion of the section, which is now wearing away so rapidly, the action may possibly be so checked as to afford time to complete the improvement. Very respectfully, W. F. RAYNOLDS, Lieutenant Colonel of Engineers U. S. A. Brigadier General A. A. HUMPHREYS, Chief of Engineers U. S. A., Washington, D. C. OFFICE OF WESTERN RIVER IMPROVEMENTS, No. 1122 Pine Street, St. Louis, Missouri, February 6, 1871. COLONEL: I have the honor to submit herewith my report on the examination of Vicksburg Harbor and vicinity, executed in accordance with your instructions of November 14, 1870, copies of which accompany this report, (papers marked A, B, C, D and E.) As neither funds nor time were available to execute a survey on the scale recommended by Colonel Macomb, I confined my examination to the immediate vicinity of Vicksburg. A careful survey was made of the peninsula opposite the city from the military canal to the point. This survey embraces all features of interest or importance, and was connected with all preceding surveys of which I could obtain maps. The left bank of the river was fixed by triangulation from the main line. A careful reconnoissance of this shore was also made from King's Landing to a point opposite the lower end of the canal and the topography filled in. Our survey was also connected with the city maps in the same manner. Two lines of levels were run across the point, viz. one along the course of the old canal, and one at the point where the cut-off seems most imminent. Frequent profiles were also made of the river bank. Borings were made at three different points on the cross section line at the narrowest point of the neck. The borings give a very good idea of the disposition of the strata. The hydrographical work was confined to making with much care four characteristic sections of the river, viz, three on the upper and one on the lower side of the point. The river during my survey reached a point 43. 6 below the high water of 1858, as determined by the bench mark left by the Delta survey on the north wall of the Prentiss House. It was consequently at its lowest stage, or very near it. All hydrographical observations are referred to this lowest observed level. Accompanying this report are three maps, viz: Sheet No. 1, showing the vicinity of Vicksburg. This map embodies all the information collected by my surveys, and gives the shore lines of 1828, 1865, 1866, and 1869 in addition. Scale, Tzbou. Sheet No. 2 gives a sketch of the Mississippi River from Terrapin Neck, above, to Grand Gulf below Vicksburg. This sketch was made from the steamer Octavia in 1869 and in 1870, and although not strictly accurate, yet is sufficiently so to give a good idea of the shape of the river in this vicinity. Scale, one inch one mile. Sheet No. 3 gives, to various scales, the profiles, cross-sections, and borings executed by my party. REPORT ON VICKSBURG AND VICINITY. The city of Vicksburg possesses the most commanding site and the finest harbor on the Mississippi River. The city is built on the range of bluffs which form the southern limit of the Yazoo bottom, and which at this point are directly on the river, the rock on which they rest cropping out at the water's edge. There is deep water along the whole city front, and in fact the entire width of the river is available for boats at all seasons, as there is not less than 25 feet depth in any part of it. Vicksburg is situated in one of the finest cotton districts of the South, and is in fact the only available outlet for a good portion of Northeastern Louisiana and Western Mississippi. It is also the shipping point for the whole country bordering on the Yazoo and its tributaries. Two lines of railroads converge there, viz, the Vicksburg, North Louisiana and Texas in Louisiana, and the Vicksburg and Meridian in Mississippi. The terminus of the former road is at Delta, three miles below Vicksburg, and on the other side of the river. It was originally at De Soto, directly opposite Vicksburg, but that site was abandoned, owing to the rapid encroachments of the river. These two roads, I understand, entirely fail to meet the demands made on them for transportation. The finest and largest packets on the Mississippi River run between Vicksburg and New Orleans, the trade being the most profitable one on the river. Of the importance of Vicksburg, in a military point of view, but little need be said. It is a perfect Gibraltar against an attack either by land or water, and may truly be said to be the key of the Mississippi Valley. Its growth since the war has been considerable, and is steadily on the increase. The present value of taxable property in the city is estimated at something over $7,000,000. In view of all this it is not surprising that the inhabitants feel justly apprehensive of a catastrophe which would at once deprive them of all their present advantages, and force them either to remain an inland town or go to the expense of extending the business portions of the city indefinitely to suit the changes which the eccentric river seems disposed to make. The conformation of the river in this vicinity is peculiar, and merits a brief description. Young's Point, Louisiana, is opposite the mouth of the Yazoo and six miles due west from Vicksburg. The course of the river at this point is a little south of east for three miles, till it reaches the head of the military canal, when it bends sharply to the northeast and maintains this direction till it reaches the bluffs on which Vicksburg is built. It then turns abruptly on itself, running nearly parallel to its former course, straight past the city, and so on for a distance of about eight miles, when it bends back to the left to reach the town of Warrenton, Mississippi. This peculiar formation explains the fine harbor of Vicksburg. The river is so concentrated by its abrupt change of direction, on reaching the bluff, the materials of which are substantial enough to prevent any great abrasion, that it is forced to scour out a very deep and narrow bed ; which possesses a directness to be seen at no other point on the river. No changes of any consequence have taken place in this portion of the river, the shore line of 1828 being almost coincident with the line of 1870. On the upper or northwestern side of the peninsula, however, the case is widely different. Near the upper mouth of the canal the direction of the river is changed so ab ruptly as to throw the whole current against the Louisiana shore. The soil is mainly composed of sand, free from cementing materials. The water, even at a dead low stage, attains an average depth of 52 feet, within 275 feet of the foot of the bank, and the average width of the water-way being but 2,000 feet, the current attains a tremendous force to abrade the soft and yielding shore. The abrasion was gradual, but constant, until 1865, since which it has attained a rate of progress most alarming. In 1828 the width of the peninsula at the site of the canal was 9,100 feet, and gradually diminished from this width to about 6,000 feet near the point. In 1858 the width had been pretty uniformly reduced about 1,900 feet from that of 1828. The maximum erosion amounted to 2,000 feet, which for thirty years gives a rate per annum of 66 feet. In 1865 the abrasion was still nearly uniform along the whole point. The maximum since 1858 was 440 feet, giving a rate for the seven years of 63 feet per annum, nearly the same as before. In 1866 a great change took place. The rate of abrasion at the upper end of the bend was enormously increased. It amounted during the year to 300 feet at the canal, 900 feet a quarter of a mile below, and 500 feet half a mile above Cramer's house. From this point the new shore line gradually ran into that of 1865. This was the year of the formation of Terrapin Neck cut-off. Of 1867 and 1868 we have no i formation, but in 1869 a crevasse took the shore line back some 1,400 feet on the line of the canal. This was exceptional, however, the regular abrasion amounting to some 950 feet since 1866, and it ceased a mile below Cramer's. This would give a rate of 317 feet per annum. The shore now showed a deep reëntering below and in the neighborhood of the canal. This was partly reclaimed by new levees. But from 1869 to 1870 the greatest amount of damage was done. The main body of the river was shifted far down the bend, the point of impact being just above Cramer's house, and the whole shore line below there was changed to suit this new direction. The average amount of cutting was 940 feet, but the maximum was 1,500 feet, and that of the narrowest part of the peninsula. At the time of my survey the width at this point was 2,500 feet, which is all that now remains to prevent the river from breaking through. This same high water filled up the head of the bend considerably, the shore line at the canal being now out beyond the line of 1866. A bar is rapidly forming above the canal, and will doubtless soon extend down to the small point shown on the map. The intervening is now occupied by an eddy, the main current only reaching the bank near the broken levee above Cramer's house. The present width of the peninsula at the canal is 6,833 feet. Two and a half miles from here this width is gradually diminished to 2,500 feet. From this point it gradually increases, attaining a width of 3,200 feet within a mile of the point. The extremity of the peninsula has been continually elongated to keep pace with the cutting of the bank above the Vicksburg bluffs. Its extremity is now about 2,000 feet beyond the line of 1828, and is a little farther down the river. As before stated, the changes in front of Vicksburg have been very slight. Such "makes" as have been formed have been speedily washed away again, leaving the shore line comparatively unchanged. There is, therefore, nothing to compensate for the wear above; and, under the best of circumstances, it would only be a question of time as to when the peninsula would be entirely washed away. At the rate given from 1828 to 1865, the peninsula would have outlived this century; but if, as seems probable, the present rate of erosion should continue, two or three years would be sufficient to effect the cut-off. Terrapin Neck, in 1858, is reported to have been 1,200 feet wide. In 1866, just previous to the formation of the cut-off, the width had been reduced to 450 feet, or a rate of abrasion of 94 feet per annum. Davis or Palmyra cut-off was 2,700 feet across in 1858. In 1867, the year it broke through, it had been reduced to about 1,200 feet, or a rate of abrasion of 166 feet per annum. In both these cases the neck was wearing on both sides, so that the actual rates of cutting were only half those given. This will give a good idea of the tremendous force now acting on the point in front of Vicksburg. The fact, too, that at Davis's cutoff, the river broke through 1,200 feet in a single night, shows the imminence of the danger now threatening the city of Vicksburg. There is no doubt in my mind that the formation of these two great cut-off's was the cause of the very marked results visible since 1865. Their combined effect was to shorten the river some thirty miles, with a proportionate increase in the water slope. The efforts of the river to regain its lost regimen are made evident by the rapid cutting going on in all the bends for some distance above and below Vicksburg. It is only in this manner that the river can regain its original length and slope. Data are wanting to determine how nearly this result has been obtained, and consequently it is impossible to predict when this excessive rate of abrasion may cease. The low-water slope at the present time is three-tenths of a foot per mile. Moreover, the encroachment of the river in various places already complicates the question, as no man can foretell what the effect of certain changes now in progress may be. For instance: the river is encroaching very rapidly on the shore opposite Paw-Paw Island; already it is only separated from the Yazoo by a neck about 1,200 feet wide, and there is no reasonable doubt but that in a year or two it will break through into that stream. No one can doubt that the change of direction thus produced will have an important bearing on the river above Vicksburg, but whether it will be for the better or for the worse it is impossible to say. It is also necessary to state here that no great flood has taken place since 1857. It is only reasonable to suppose that a great flood rising above the banks will produce far greater effects than the comparatively small ones of late years. The borings execnted under my directions gave most disheartening results. About five feet above the lowwater level of the river, a bed of blue clay, three feet thick, is met with; above this is the usual sandy surface soil; 19 feet below the first layer of clay, a second one, 4 feet thick, is met; the space between the two is filled with coarse sand, thoroughly permeated by the seep water from the river, and almost fluid; at a farther depth of 19 feet a third layer of clay is met with, which is 18 feet thick, above which is quicksand, as before. Twenty-eight feet below the third layer of clay is solid rock, and the space between is filled up with some substance too soft to be raised by the boring tools. It is probably an almost fluid quicksand. By referring to the sheet of cross-sections, &c., it will be seen that a large portion-at least of the present river bed—is in the third layer of clay, but the upper section, taken where the water-way is most contracted, (1,400 feet wide at the surface,) shows a depth which would carry it through this clay, and in all probability down to the Neck. We therefore see that the whole extent of the upper side of the peninsula presents nothing to resist the action of the river but unstable layers of sand of great thickness which are already permeated by the river water to a distance of at least 500 feet from the river itself, and probably much farther. In fact, there is nothing to show that the water does not already flow through from one side of the point to the other, and, indeed, the almost fluid condition of the lower strata points strongly to that inference. The cutting action of the river merely washes out this loose sand, thereby undermining the clay layers which finally break down under the superincumbent weight, and precipitate considerable portions of the bank into the river simultaneously; of course, the deeper the water the more rapid the cutting from the increased hydrostatic pressure and the greater overbearing weight. The present bed of the river, as well as the slopes of the banks, are apparently curved with lumps of clay which are lying as they fell, the sand having been all washed out from around them. The precise course which would be taken by the river in case the threatened cut-off should form, is hard to predict, but the effects on Vicksburg Harbor are obvious enough; should the river go through at the present narrowest part of the neck the main channel would strike the Mississippi shore about two miles below Vicksburg, and the tendency, for some time at least, would be to work further down the river. The present harbor would soon be filled up with sand bars, and as no affluent enters it of sufficient size to keep open a channel large enough for navigable purposes, the present city wharf would be entirely shut off from the river. The result of all previous cut-offs have shown conclusively that the filling up of the old bed is inevitable. It would be impossible to keep the upper end of the old channel open, although the lower end might be opened up by dredging. The channel thus obtained would, however, be too small and dangerous for large or heavily ladened boats, so that the city would be practically shut off from the river. There would, therefore, remain no alternative but to establish new warehouses, &c., at the nearest point available on the new channel, which would probably be some two or three miles from the present city wharf. The worst feature about the change would be the loss of the bluffs and the stable river regimen which the city now enjoys, and which have been the main sources of its prosperity. There would also be a great uncertainty as to the stability of any new site which might be selected. The best and most economical method of preventing this calamity is not very obvious. It is a favorite idea among non-professional people that it is the easiest thing in the world to change the course of a river in any manner desirable. In view of this fact it is not surprising that parties interested in the matter should have broached a great number of schemes for preserving Vicksburg Harbor, all of which are based on some idea of changing the course of the river. Now the chronicles of engineering science, while recording innumerable failures of works of this nature, mention but few successes, In fact, it may safely be stated that no problem in engineering offers more uncertainty as to the results, and fewer chances of success. That successful works of this kind have been carried out is unquestionable, but it has been at a fabulous cost of time and money, and at best only on small or medium size streams. To apply such experience to a river like the Mississippi at Vicksburg would be impossible. To carry out any work of this kind many years of preliminary observation are absolutely essential. To predict the effect of a cut-off or a change of direction in the river it should be closely studied at all stages and for several successive seasons, and the observations should extend over a sufficient portion of the stream to embrace the |