the zero of the gauge; at Hannibal the elevation is 488 feet, and is 31.6 feet above the zero of the gauge. The gauges in each case are on the bridge. Eight hundred and fifty-three sections of the river were sounded. The greatest channel depths found were 36 feet at Hannibal bridge, and 34 feet just above Alton. Least channel depths found were 34 feet at Mosier's Landing and Tisdale's towhead. The greatest depth of water found was 66 feet just below the east pier of the Louisiana bridge. To the efficiency and hearty good will of my assistants is due the success of the season's work, and I am pleased to commend them most heartily as competent, energetic, and faithful workers, and to thank them personally for their friendliness. Very respectfully, Capt. CARL F. PALFREY, F. B. MALTBY, Corps of Engineers, U. S. A. APPENDIX 4 E. REPORT OF ASSISTANT ENGINEER A. T. MORROW ON CAVING BANKS AND CONDITION OF SURVEY MARKS FROM CAIRO TO DONALDSONVILLE, LOUISIANA. ST. LOUIS, Mo., April 16, 1892. CAPTAIN: I have the honor to make the following report of the operations of the party which has been under my charge for the last three months: The party was organized with Assistant Engineer F. B. Maltby in charge, who, with four assistants and a crew of about twenty men, quartered on the steamer Patrol, began operations at Cairo, Ill., on November 20, 1891, the object of the expedition being to make surveys of the caving bends and to inspect the marks of previous surveys from that point to Donaldsonville, La. The work had progressed as far as Commerce Landing, 40 miles below Memphis, when on January 1 the steamer Patrol was caught in a gale and sunk. The party was then transferred to the steamer Kerns and resumed work on January 8. On January 16 I joined the party at Helena, Ark., and succeeded Mr. Maltby, who had offered his resignation. From that point the work proceeded without interruption to Donaldsonville, La., where on March 22, in obedience to your orders, I discharged a part of my force and returned with one assistant and a small force of men to complete some fragmentary portions of work on bench marks which had been omitted. on account of snow, and in order to properly balance the duties of the force. The work was entirely completed on April 6, and on April 11 I reached Cairo where I turned over the property and discharged the remainder of my men. During the progress of the work the field notes of each day were platted on the succeeding day, and the plats were forwarded to the office as opportunity offered. In the start only the portions of the river bank which had undergone change were surveyed, but, as it afterwards proved, it could not always be determined on the ground whether or not changes had taken place since the old surveys; and as such determinations surely could not be made in advance of the work, the topographical work developed into a complete survey of the bank lines of the river, the concave portions being surveyed with transit and stadia, with frequent connections on old survey marks, and the opposite bank by intersections at points as frequent as required in view of the constant changes occurring with the varying stages of water. In advance of the shore-line parties two parties of stone hunters were kept at work in order to furnish connections for the topographers and to redescribe or replace such old survey marks as were still in existence. This work proved to be the more laborious part of our duties, and it often became necessary to call upon the shoreline parties for assistance, thus considerably extending the time that would have been necessary to do the shore-line work alone. The result of the search for marks of the old surveys are as follows: Entire number of ordinary bench marks looked for were 920, of which 635 were found. Entire number of precise bench marks looked for were 130, of which 70 were found. Entire number of triangulation stations looked for were 410, of which 101 were found. Entire number of marks of all classes looked for were 1,460, of which 806 were found. Entire number of marks caved in the river............. Entire number of marks covered by sedimentary deposit and levees... Entire number of marks broken or otherwise destroyed.. Entire number of marks not accounted for. 180 127 37 32 255 Probably a large percent of the marks not accounted for could be found with sufficient search, and many of those covered by sedimentary deposit could be restored by sufficient labor. Enough marks, however, have been found in all localities to furnish connections for future surveys. The small number of triangulation stations remaining is due to the fact that they were generally placed near the banks and have been destroyed by the changes of the river. Of the various kinds of bench marks established by the old surveys, the flat stone and iron pipe are unquestionably the best. The pipes standing well above the surface are easily found and have seldom been covered by the sedimentary deposits which so completely conceal a large number of stones and cement posts. Precise bench marks consisting of copper bolts in brick chimneys and brick foundations have not been well preserved, a large per cent of them having been destroyed by improvements or changes in the buildings, which are largely of a temporary character in those localities. A large per cent of the marks placed on or near levees have either been buried under additions or have been destroyed by other changes or improvements. Marks which were placed by the side of public roads or along land lines seem to have been best preserved. The changes that have taken place in the river are so varied and apparently so devoid of uniformity that any opinions in regard to them which were formed on the ground at the time of the survey would not be of value in comparison with conclusious derived from a subsequent study of the maps of the surveys. The distance from Cairo to Donaldsonville by river is about 880 miles, and the whole time consumed by the expedition from its departure to its return was one hundred and forty-one days. Deducting the time lost by the wreck and consumed by the return trip, the time required for the survey (including Sundays and days lost by bad weather) was one hundred and fourteen days, showing an average daily progress of 7.7 miles. The work of the survey was considerably retarded by the work of searching for stones, and consequently the rate of progress was considerably below that which could have been made by the survey alone; but is sufficient to illustrate with what facility such surveys can be made by transit and stadia when untrammeled and in the hands of skilled topographers. Very respectfully, your obedient servant, Capt. CARL F. PALFREY, Corps of Engineers, U. S. A. A. T. MORROW, APPENDIX 4 F. REPORT OF ASSISTANT ENGINEER J. A. OCKERSON ON CAVING BANKS FROM CAIRO TO DONALDSONVILLE, WITH TABULATED RESULTS AND PLAT. OFFICE MISSISSIPPI RIVER COMMISSION, St. Louis, Mo., May 31, 1892. CAPTAIN: I have the honor to submit the following tabulated results derived from a study of the recent caving bank survey of the Mississippi River from Cairo to Donaldsonville, and a comparison of the same with previous surveys. In order to make a ready and accurate comparison, the shore line of the survey of November, 1891, to March, 1892, was platted on the detail charts of the old surveys, mostly made from 1879 to 1883, and the area between the shore lines was carefully measured with a planimeter. This gave the area of caving. The data for the depth of caving was derived from the old detail charts, which show the height of bank above datum, elevation of water surface, and depth of water. From this the height of the bank above the bed was easily deduced. Where the river had maintained its width and the channel lay close to the caving bank the height of the bank deduced was measured from the deepest part of the bed to the top of the bank. Where the channel lay some distance from the bank and the caving had widened the stream without shifting the channel materially, then the average depths between the thalweg and the depth near shore were taken as the depths of the bed and the heights of banks deduced accordingly. The dates of the surveys of each section considered are given in the table and from them the average amount of erosion per annum was derived. An inspection of the maps shows that caving rarely occurs on both banks of the river at the same time in the same locality. It shifts from bank to bank, and as it ceases on one side it begins on the other, so that the caving areas often slightly overlap each other. The total length of caving banks from Cairo to Donaldsonville, a midstream distance of 885 miles, is 921 miles. About 15 miles of this pertains to islands. With a very few exceptions there is more or less caving in all of the bends, but the amount of caving does not seem to bear any definite relation to the curvature. The maximum caving occurs in comparatively straight reaches, such as Leota, Raleigh, Milliken, Carlyle, Oak Bend, etc., while the extraordinary bends above Greenville show caving far below the maximum. Darnell Point, 80 miles from Cairo, is an example of excessive caving in a long, straight reach of river. The annual erosion per mile of river reaches its maximum in the vicinity of Raleigh. In the vicinity of Oak Bend, below Vicksburg, it reaches nearly the same amount. After passing Natchez the erosion becomes rapidly less and from the Red River down it is quite small in amount. The character of vegetation on the banks has no apparent influence on the extent of the erosion. In a caving bend which is partly cultivated and partly timbered the shore line curve is smooth and regular, showing that they are eroded with equal facility. Of 37 localities between Cairo and Vicksburg where depths of less than 10 feet were reported in 1891, 21 were found to be at the foot of or immediately below rapidly caving banks. The amount of erosion given in these tables is doubtless considerably less than the total movement. In some localities where rapid caving was going on at the time when the first surveys were made now we find a heavy fill. Opposite Commerce, Miss., is a case of that kind, where a caving bank in 1879 has filled about 2,000 feet in width and about 5 miles loug, a part of which is now cultivated. It is not improbable that there are places where the process of scour and fill has been repeated several times during the intervals between the surveys. The total movement by erosion would probably exceed the amount given in tables by about 15 per cent. The average annual amount of erosion, as derived from the tabulated results, is found to be about 9 acres in area by 66 feet deep for each mile of river; or a total for the river between Cairo and Donaldsonville of 10 square miles by 86 feet in depth annually. Erosion does not necessarily mean a widening of the bed of the river. The eroded bank is generally followed by an equivalent fill on the opposite bank, and in some localities of excessive erosion the bed has actually grown narrower. The composition of the banks is not given in sufficient detail to determine the relation, if any, between character of banks and erosion. In the region of excessive caving the banks are largely composed of sand. In some localities, where the banks are described as being clay, the erosion has been slight. Respectfully submitted. Capt. CARL F. PALFREY, Corps of Engineers, U. S. A., Secretary. J. A. OCKERSON, |