remove the material bodily and can itself be easily moved from place to place, is essential in order to give a reasonable chance of success. In view of the very serious loss which the trade of the valley was suf fering from the obstructions of last autumn, the commission, though not very sanguine, was willing to try the experiment of dredging, provided a dredge such as it considered essential could be secured. There was but one such in the Mississippi River, the dredge Bailey, employed at the South Pass. Efforts were made to obtain her, but they were fruitless, her services being required by her owners at the South Pass. The commission has had under consideration the propriety of building a dredge for this experiment, but in view of its very considerable cost has not yet concluded to do so. The obstructions during the low-water season were of course greatest above Cairo. Between Cairo and the mouth of White River, there were 42 crossings giving less than 10-feet channel depth, of which 35 had less than 9 feet, 26 less than 8 feet, 21 less than 7 feet, 8 less than 6 feet, and 1-at the head of Island 40-had 5 feet. FINANCIAL STATEMENTS. Appropriation for salaries and expenses Mississippi River Commission: Balance on hand July 1, 1891.. $80.91 Refundment by Capt. Powell, for account Mississippi River Commission... 57.35 Approximate outstanding liabilities and amounts covered by existing contracts. 249, 046. 98 C. B. COMSTOCK, Col. of Engineers and Bet. Brig. Gen., President Mississippi River Commission. The SECRETARY OF WAR, CHAS. R. SUTER, Lieut. Col. of Engineers. B. M. HARROD, R. S. TAYLOR, O. H. ERNST, Major of Engineers, Col. U. S. Army. HENRY FLAD, C. E., HENRY L. WHITING, U. S. Coast and Geodetic Survey. Through the Chief of Engineers, Washington, D. C. LETTERS OF THE MISSISSIPPI RIVER COMMISSION SUBMITTING ESTI- ST. LOUIS, Mo., August 16, 1892. GENERAL: Your letter of August 4, calling for estimates from the Mississippi River Commission for the fiscal year ending June 30, 1894, failed to reach me in time to be laid before the Commission at their recent meeting. It was supposed by the Commission that estimates in the usual form would not be required, since the act of July 13 specifically designated the amount which can be expended during each of the four years provided for. It was, however, supposed that a recommendation covering a detailed project for this expenditure would be required before the next meeting of Congress, and instructions were given to the secretary and to the district officers to have projects prepared for works under their charge in time for the next meeting of the Commission, November 5, 1892. As these projects are intended to cover the whole amount allowed by law for the year ending June 30, 1894, after deducting the $1,500,000 already recommended for expenditures on levees during that year, the gross estimate of the Commission for the fiscal year ending June 30, 1894, may be placed at $2,665,000. Separate estimates for continuing work on harbors have already been submitted. Very respectfully, your obedient servant, Acting President, Brig. Gen. THOMAS L. CASEY, CHAS. R. SUTER, THE MISSISSIPPI RIVER COMMISSION, New York City, August 8, 1892. GENERAL: In compliance with the requirements of the river and har bor acts of 1866 and 1867, I have the honor to submit estimates for improvement at certain points on the Mississippi River, for the fiscal year ending June 30, 1894, viz: Lieut. Col. of Engineers, President pro tem., 1 LIST OF APPENDICES ACCOMPANYING THE FOREGOING REPORT. Appendix 1. Effects of Ames Crevasse, March 16, 1891, with diagrams, and *Appendix B of Annual Report, 1891, with its diagrams not then forwarded, Col. C. R. Suter. 2. Report on study of velocity of flood travel, with diagrams and subreport of Assistant Engineer Seddon, Col. C. R. Suter. 3. Report on survey of Nonconnah Rocks, with project for removal, Capt. S. W. Roessler. 4. Report of Capt. C. F. Palfrey, secretary of the Commission, with subreports appended, as follows: A.-Secondary triangulation, Keokuk, Iowa, to Port Louisa, Iowa, with tabulated results, description of stations, and plat, Assistant Engineer Stewart. B.-Precise levels, St. Paul, Minn., to Savanna, Ill., field work, reduction, tabulated results, and descriptions of bench marks, Assistant Engineer Ferguson. C.-Precise levels, Duluth, Minn., to St. Paul, Minn, field work and reduction, with tabulated results and descriptions of bench marks, Assistant Engineer Paige. D.-Topographical and hydrographical fieldwork, Assistant Engi- E. Caving banks and state of permanent marks, Assistant Engineer F.-Caving banks, areas, and volumes, with graphic summary, As- H.-Discharge measurements, 1891. 5. Report of Capt. S. W. Roessler on operations in first and second dis- A.-Plum Point Reach, Assistant Engineer Nolty. 6. Report of Capt. C. McD. Townsend on operations in third district, with A.-Ashbrook Neck, Assistant Engineer Hider. C.-Louisiana Bend, Assistant Engineer Tollinger. D.-Vicksburg, Assistant Engineer Coppée. E.-Surveys, etc., Assistant Engineer Hider. 7. Report of First Lieut. John Millis on operations in fourth district, LIST OF PLATES ACCOMPANYING THIS REPORT. Diagram showing effects of Ames Crevasse. (Appendix 1, first paper.) Hydrographs, profiles, and gauge relations, Plates I-VIII.* (Appendix 1, second paper. *) Gauge relations, velocities, and time intervals, Plates I-VII. (Appendix 2.) Graphic summary of caving banks. (Appendix 4 F.) Map of Plum Point Reach. (Appendix 5.). Map of Mississippi River near Memphis. (Appendix 5.) Map of part of second district showing levee works by United States in 1891-'92. (Appendix 5.) Map of Ashbrook Neck. (Appendix 6.) Map of Greenville. (Appendix 6.) Map of Louisiana Bend. (Appendix 6.) Map of Lake Providence Reach. (Appendix 6.) General map, fourth district. (Appendix 7.) Works at junction of Mississippi, Red, and Atchafalaya. (Appendix 7.) New Orleans Harbor. (Appendix 7.) Carrollton Bend. (Appendix 7.) Third District Reach, New Orleans. (Appendix 7.) * Not printed. APPENDIX 1. REPORT OF LIEUTENANT COLONEL CHARLES R. SUTER, CORPS OF ENGINEERS, UPON EFFECTS OF AMES CREVASSE, MARCH 16, 1891. * ST. LOUIS, Mo., June 14, 1892. GENERAL: I have the honor to submit herewith a diagram which exhibits graphically the effects of the Ames crevasse, which occurred opposite New Orleans on March 16, 1891. The diagrams are prepared in a manner entirely similar to those which were submitted to the Commission last year to illustrate the effects of the "Nita" and other crevasses which occurred below Red River in 1890.* The present instance is very interesting, as it was the only crevasse that occurred, and hence there are no complications of the effect produced. Bayou Sara is taken as the upper station on this diagram, as the effect of the crevasse did not extend above Baton Rouge. In the accompanying tabulation are given for each station the maximum effects of the crevasse, that is to say, the difference between the heights which theoretically should have been produced by the maximum reading at Bayou Sara, and the readings which actually did correspond to it. The maximum reading at Bayon Sara occurred on May 1, the crevasse having taken place March 16. The effect of this large crevasse, which discharged very nearly 100,000 cubic feet per second, died out completely at Baton Rouge, 126 miles upstream, and after running for six weeks it had only relieved the river at Carrollton, 2 miles above, to the extent of 1.9 feet. If the crevasse had not occurred the Carrollton gauge would have reached an elevation of 16.3 feet, or 0.3 foot higher than the actual maximum reading. On the diagram is shown by a full line the gauge relation of 1890; that of 1891, shown by a broken line, is about two-tenths lower at Carrollton. interesting feature of the diagram are the abnormally high readings at all the stations except Carrollton prior to February 16. As this feature shows most prominently at those gauges nearest the "Nita" and other large crevasses of 1890, it seems probable that it was due to deposits caused by those crevasses, which were swept out by the rising river about the date mentioned, lowering the gauge relation to the extent of about half a foot. An Table showing lowering effect of Ames crevasse at different points above and corresponding to the crest of the flood at Bayou Sara, May 1, 1891. REPORT OF LIEUTENANT-COLONEL CHARLES R. SUTER, CORPS OF ENGINEERS, UPON THE VELOCITY OF FLOOD TRAVEL ON LOWER MISSISSIPPI RIVER. ST. LOUIS, Mo., June 14, 1892. GENERAL: I beg leave to submit herewith, for the information of the Commission, the results of further study of the velocity of flood travel on the Lower Mississippi. This subject was alluded to in the paper submitted by me under date of August 3, 1888 (published as Appendix A to the Annual Report of Commission for 1891), but for lack of time could not then be elaborated as fully as desirable. The conclusions there stated were derived from a comparison of hydrographs, and of discharges simultaneously measured at different points along the river. The determinations of *Printed in Annual Report, Chief of Engineers, 1891, page 3444. 1 velocity of travel were only approximate, but such corrections as are now made are not sufficient to materially affect the other conclusions embodied in the previous paper. In that paper the gauge relations were constructed by using the approximate time intervals determined as stated above; in the present case the intervals are determined from a careful study of the gange relations themselves. The method used, exceedingly ingenious and interesting, was devised by my assistant, Mr. Seddon, and is fully described in his report to me, a copy of which is appended, and to which reference is made for all details. Briefly stated the method used depends upon the fact that where no tributary increment is received, the readings at a downstream gauge which correspond to those of a gauge upstream should be alike for both rising and falling stages. If they are not, the interval allowed is either too long or too short. By taking trial intervals varying by one-tenth of a day, the smallest fraction that can be reasonably well used in interpolating between the recorded gauge readings, and by studying each rise and fall separately, the interval can be determined to within about a half a tenth a day, or about an hour and a quarter, and this is probably as close an approximation as can well be expected with gauge readings such as are now taken. The sections of river between the main tributaries are taken separately, the uppermost gauge being compared with each of the lower ones in succession. Thus for the section Cairo-Helena, the Cairo gauge is compared successively with those at Belmont, New Madrid, Cottonwood Point, Fulton, Memphis, Mhoons, and Helena. In this way gradually lengthening intervals are obtained, a constant check on the accuracy of the method is furnished, and any tributary effect can be readily determined. As the limit of error in the determination of the interval is a constant one, its percentage of the total will of course vary, and the long intervals are therefore more accurately determined than the shorter ones. In passing from one basin to another it is necessary to choose such periods as are not complicated by tributary increment. This materially reduces the range of the observations, and the interval can not be considered so well determined as in other cases; still, it is not thought that any material error is incurred. The rates of travel as thus determined are given in Mr. Seddon's paper in tabular form and are also exhibited graphically. The rate from Cairo to Red River Landing is 82 miles per day, instead of 75, as previously assumed, and at intermediate points the rate varies both ways from this mean. Below Red River the rate increases enormously and progressively as we descend the river. But for each reach between gauges the rate is constant from the lowest stages to the highest at which the river may fairly be considered to have adjusted its channel; that is, for all stages short of overflow. This constancy of rate, irrespective of stage, and of the variations in the measured velocity, is very puzzling. Attempts to ascertain the mean velocity at different stages over long stretches of river have been made, and the details will be found in Mr. Seddon's paper. The results, however, still show considerable variation with stage, although these variations are less than in the case of individual sections. The conclusion, therefore, seems unavoidable that some form of transmission similar to wave movement is involved. In the deep river below Red River Landing nothing else will explain the very high rate which is noted, and above that point it seems possible that the deep pools may exert a controlling influence in the same direction, especially at low stages when their influence would be most preponderant. At the higher stages, when their influence would naturally be less, the rate does not vary greatly from the mean velocity between Cairo and Red River Landing. In further support of this view, an examination of the tabulation of local rates (Tabulation I) will show that the highest velocities occur on those portions of the river where deep pools preponderate, and the lowest velocities where the mean depths are a minimum. Premising that in such an examination the absolute depth on the bars between the pools need not be considered, but only the relative length and depth of pools and bars throughout the reach considered, attention is especially called to the reaches Cairo-Belmont, Cottonwood Point-Fulton, Arkansas City-Greenville, and St. Joseph-Natchez, as examples of high velocities combined with a marked preponderance of deep pools, and to the reaches of Memphis-Mhoons and Mhoons-Helena as examples of the converse. An apparent exception to this rule is found in the reach Vicksburg-St. Joseph, which can only be explained by the relative shortness and imperfection of the St. Joseph record, which renders the determination of the local rate at this point somewhat uncertain. All this evidence seems to indicate that an increase in mean depth will increase the rate of flood travel, and as a rapid and unimpeded discharge of flood waters is the surest guarantee against excessive flood heights, the bearing of these investigations is thought to be of sufficient importance to justify their publication. Very respectfully, your obedient servant, Gen. C. B. COMSTOCK, President Mississippi River Commission, CHAS. R. SUTER, |