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Delta Point.--Yo work has been done, but several slips in the bank above the revetment show erosion there which will require extension of the revetment up.stream.
Levees-Tensas Front.-With an allotment of $56,500 for the levee from Amos Bayou to Arkansas City, and a later allotment of $155,083 for levees from Amos Bayou to the Louisiana State line, work has been carried on along the whole front. It had been decided by the Com. mission to build the line 3 feet above the highest water from Amos Bayou to Lucca Landing; from there to Arkansas City 2: feet, and the rest 2 feet, except at lake crossings, where greater height would be given. This work has been finished, with the exception of a portion below Lucca Landing, where caving is feared, and the Whiskey Chute levee, where extensive sinking has delayed completion.
The escape on this front, from Amos Bayou to the lower limit of the district, opposite Warrenton, Miss., during the last high water, has been confined to a gap left in a part of the work done in the State of Arkansas by the State of Louisiana, and a small break near Grand Lake; the levees, with these exceptions, being continuous. Considerable sink. ing has occurred at Lake Chicot crossing, and more may be expected.
For details, see report of Captain Rossell, Appendix H.
(Warrenton, Miss., to Head of Passes—484 miles. Officer in charge, Capt. D. C. Kingman, Corps of Engineers, New Orleans, La.)
Harbor of New Orleans.-In Gouldsboro Bend one new spur has been constructed and two others raised to grade, completing the system of six spurs, as projected. Examination shows that the construction has protected the bank; it can not be discovered, however, that any deposit between the spurs has been induced.
Rectification of Red and Atchafalaya rivers.—The location fixed upon for the first of the projected system of six submerged dams in the Atchafalaya is about 500 feet below the Bayou des Glaizes. The mattress sill for this dam has been laid during the year, and connected with the levees on each side by earthen dikes sodded or (if below ordinary high water) paved with stone.
For the maintenance ofa navigable channel in lower Old River, $15,000 was allotted. This was expended during the low-water season in an ineffectual attempt to keep the channel open by the methods heretofore used. The failure was due to the same causes as in the preceding year, viz, the forcing up of the bottom by the weight of the banks, as the river fell, and the absence of scouring force due to the simultaneous decline of both rivers, •with feeble currents in alternating directions. Navigation was closed from the beginning of August to the middle of December.
Levees.-With allotments amounting to $105,000, the Deer Park levee has been built, and up to May 30 about one-half of the new Kempe levee. The State and district authorities have undertaken the closure of Diamond Island gap by a levee nearly 7 miles long, of which about two-thirds has been completed. Repairs have also been made to the levee at Shipp's Bayou and to Glasscock's levee, which had been again damaged by beavers.
When work now in progress is completed the only gaps in levees in this district will be Bougère Crevasse, 23,400 feet long, and from Black Hawk to Red River, about 90,000 feet.
Surveys in Morganza Bend 'show an increase in area of the river sections both above and below the site of the crevasse since its closure. For details and a discussion of the Atchafalaya problem, see report of Captain Kingman, Appendix I.
No appropriations for the expenses of the Mississippi River Commission have been made since July 7, 1884. The result has been that the Commission has been unable properly to perform its duties or to examine the works for which it is reponsible. No inspection by the Commission of the works along the river has been possible since November, 1885, on account of lack of funds.
The river and harbor act of August 5, 1886, limited the Commission in the use of revetment to so great a degree as to make it unadvisable to attempt much work on the Plum Point and Lake Providence reaches with the funds it provided. The result of this limitation has been loss of work and increase in the final cost of improvement. The last work of any importance on these reaches was with the funds provided by the river and harbor act of July 5, 1884; thus, during a long interval of time, the works have been exposed to the attacks of the river, and for all wood-work above water to great injury by decay. In the Plum Point Reach, while some work has been lost, the injury as yet has not been arge, but the works in the Lake Providence Reach are now in a very unlatisfactory condition.
Appropriation for salaries and expenses Mississippi River Commission:
Balance on haud July 1, 1887.
Balance on hand July 1, 1888.
Balance on hand July 1, 1887.
Balance on hand July 1, 1888.
Balance on hand July 1, 1837.
Balance on hand July 1, 1883...
437, 002, 30
ESTIMATE OF FUNDS FOR THE MISSISSIPPI RIVER COMMISSION FOR THE FISCAL YEAR
ENDING JUNE 30, 1890.
Sundry ciril bill.
penses of the Mississippi River Commission; for printing and telegraph-
River and harbor bill.
For surveys and examinations of the Mississippi River from the Head of the
Passes to its headwaters-continuing survey.
mouth of the Ohio River
For work at Hickman, Ky:--continuing improvement.
$181, 750 For work at Greenville, Miss.-continuing improvement.
230,000 For work at Vicksburg, Miss
125, 000 For work at New Orleans, La..
230,000 For rectification of Red and Atchafalaya rivers.
300,000 C. B. COMSTOCK, Lieut. Col. of Engineers,
But. Brig. Gen.,
Chas. R. SUTER,
B. M. HARROD.
Major of Engineers. The SECRETARY OF WAR,
(Through the Chief of Engineers.)
List of appendices accompanying the foregoing report.
APPENDIX A.-Second paper by General Comstock, on effect of overflow on velocity
and flood height. APPENDIX B.--Report of the secretary of the Commission.
1. Elevations and descriptions of secondary triangulation stations,
Cairo to Donaldson ville.
4. Low-water gauge-readings, 1887–83.
tricts to November 1, 1807. APPENDIX H.-Report of Captain Rossell upon operations in the third district.
i. Report of Captain Rossell upon Vicksburg survey. APPENDIX I.-Report of Captain Kingman upon operations in the fourth district.
1. Improving harbor at New Orleans, La.
List of plates accompanying the foregoing report.
November, 1887, Appendix E.
Changes in bank lines, Appendix E.
NOTE.-In consequence of the resiguation of Professor Henry Mitchell, there is a vacancy in the Commission.
EFFECT OF OVERFLOW IN DIMINISHING VELOCITY OF MISSISSIPPI
RIVER, AND EFFECT OF LE VEES ALONG YAZOO FRONT ON FLOOD
Paper presented by General C. B. Comstock at a meeting of the Commission on board
steamer Mississippi November 10, 1883.
1. In a paper dated March 15, 1831, addressed to the Mississippi River Commission and published in its annual report for 1835, I concluded : 1st, that the observations of the Commission give no support to the theory " that when food escape over the Mississippi River bauks begins the velocities in the main river are checked and deposits induced ; and the checking of velocity arises from this escape;" 2d, that * the theory that levees built in 1882-'83 reduced the flood heights at Vicksburg in 1883 as compared with 1882 is not needed to account for the facts.”
Under date of August 28, 1885, Maj. C. R. Suter submits to the president of the Commission a paper prepared in accordance with Major Sater's instructions, dissenting from those conclusions. As those conclusions were correct, the paper needs examination.
The first conclusion will first be considered. The majority of the Mississippi River Commission, in their report for 1883, say: “The loss of volume through high-water outlets causes both a diminution of velocity and a deflection of the thread of movement of the stream towards the outlet, accompanied by loss of the power necessary to transport the material with which it is loaded."
If it is true that when overflow begins, the velocity in the river is diminished by the overflow accurate velocity observations in the maiu river at the time of flood escape should establish that fact. In my paper of March 15, 1884, I showed that the Commission was then in possession of such observations at twelve points where overflow occurred, scattered from near Saint Paul to the Red River. At eleven of these points there is no decrease in the velocity of the main river, as it rises from the stage when overflow begins, to its maximum stage. At one, Hays' Landing, there is a slight decrease. At eight of the twelve stations the velocity steadily increases during this period. At three others the velocity remains about the same during this period. At two of these three, Grafton and Clayton, this constancy of velocity during the overflow period seems to be accounted for by the local slopes. At the third, Hannibal, there are not sutticient data for discussion; at one out of the twelve, namely, Hays' Landing, there are at times great irregularities in the velocities, which are at least in part accounted for by the variation in slopes; but the velocities while the river was rising from its overflow stage, January 23, to its maximum height, March 20, were quite regular. From January 23 to February 27, the velocities varied little from 5.9 feet. Between February 27 and March 20 ten velocities were measured. They are well represented by a right line giving for February 27, 1882, gange equal 37.52 feet, mean velocity equal 6 feet, and for March 20, 1832, gauge equal 38.59 feet, mean velocity equal 5.5 feet. Here is a case where the velocities diminish about 0,5 foot as the river rises towards its maximum. But in my judgment this decrease of 8 per cent. in velocity is essentially accounted for by the fact that the fall in the water-surface from Lake Providence to Hays' Landing was 4.05 feet on Feb. ruary 27, 1832, and 3.28 feet on March 20, 1892, a decrease of 19 per cent., while from Hays' Landing to Vicksburg, on the same dates, the falls were 12.98 feet and 9.87 feet, a decrease of 24 per cent. These decreases above and below Hays' Landing indicate a reduction in the slope between the two dates of about 21 per cent. at this place, which, by the ordinary velocity formula would account for a diminution in velocity of 10 per cent., or slightly more than the observed diminution. No new theory is needed to account for the difference in velocity between the two dates, February 27, 1882, and March 20, 1882.
2. 'It seems scarcely necessary to say to the Commission that slopes over long distances are used because they are the only ones available for comparisons.
While at high stages the slopes on the river become much more uniform that at low river, yet the changes in slope at a given station derived from stretches of the river above and below (the lower being 46 miles in length), must be regarded as giving only a general indication of the changes going ou in the local slope, which, however, is valuable in the absence of more accurate information.
The paper submitted by Major Suter contains remarks on the Fulton slopes and discharges of 1834, and those between Arkansas City and Vicksburg in 1822 and 1083. They add no inforination that affects my first conclusion. Every one knows tbat the
upper part of a velocity curve is sometimes irregular. The important point is, do the velocities seriously decrease when the overflow stage is reached in consequence of the water escape over the banks, and does this checking of velocity cause deposits in the river below? If the checking of velocity without any change of slope to account for it, were a fact; it certainly ought to be shown at sone one of our twelve discharge stations examined. As it is not, I can only repeat my tirst conclusion, namely, “that the observations of the Commission give no support to the theory that when flood escape over the Mississippi River bauks begins the velocities in the main river are checked and deposits induced, and that the checking of velocity arises from this escape.”
3. The second conclusion in my paper of March 15, 1884, is, that “the theory that levees built in 1882-83 reduced the flood heights at Vicksburg in 1883 as compared with 1882, is not needed to account for the facts."
Major Suter, in his letter, dissents from this. In my paper of March 15, 1884, my conclusion was based merely on the relative stages of the Mississippi River at Helena; on those of the White and Arkansas rivers at or near the time of the maximum Vicksburg gauge-reading, and on the probably smaller return flow from the Yazoo swamp in 1083 than in 1882. As the gauges from Lake Providence to Helena at the maximum stage (48.8) at Vicksburg, March 20, 1882, were higher than at the Vicksburg maximum stage (43.8) April 7, 1883, by amounts that increased from 5 feet at Vicksburg to 9 feet at Helena, this strongly indicated a smaller discharge in that part of the river in 1883. Butin my paper no attempt was made to determine the precise discharges in 1833, as the data for such a determination are far from sufficient for exactness between Helena and Vicksburg: As the paper submitted by Major Suter attempts to determine such discharges and give a value for the discharge at Vicksburg in 1883 at the maximum gange-reading which for the main river at Vicksburg is 237,000 cubic feet per second larger than the corresponding discharge in 1882 (the Yazoo swamp return flow in both years being excluded), it becomes necessary to make the best estimate possible of these discharges in 1872 and 1883 in order to show that my conclusions were correct and that the paper is not.
4. On March 20, 1882, the Vicksburg gauge reached its maximum for the year of 48.75 feet, and the discharge at Hays' Landing on that day was 937,000 cubic feet with a gauge-reading of 38.59 feet. On April 7, 1883, the Vicksburg gauge reached its maximum for that year of 43.80 fret, and the Lake Providence gange read 32.20 feet. What was the discharge at Hays' Landing on that day! There was no gauge record at Hays' Landing, and the Hays' Landing gauge-reading must be computed from the Lake Providence reading. In 1882, at Lake Providence stage of 33.20, that gauge read on an average about 0.5 foot more than the Hay's Landing gange, and 32.7 feet will accordingly be taken as the Hays' Landing gauge-reading, April 7, 1883. If the Hays' Landing discbarge curve of 1882 gave in the vicinity of this gauge-reading but a single value for the discharge that value might be taken as an approximation to the discharge there on April 7, 1823. Unfortunately, in the vicinity of 33 feet it gives widely varying values for the discharge. It is known that slope, when mean depths vary little, exercises a powerful influence on velocity. Hence, in selecting from the discharge curve of 1882 a discharge which would most probably represent that of April 7, 1883, the dates in 1882 selected should have not only gauge. readings but also slopes as nearly equal as possible to those observed April 7, 1883.
The nearest gauges read in both years were those of Greenville, Lake Providence, and Vicksburg, hence these must be used in comparing slopes. (It is not probable that the average values of the slopes would be much ditterent if Hays' Landing were to replace Lake Providence.) On April 7, 1853, the fall in the river surface from Greenville to Lake Providence was 19.13 feet, and from Lake Providence to Vicksburg was 12.98 feet.
Since the return flow from the Yazoo swamp produces most effect on slope where it enters the Mississippi, and the effect nearly disappears in going up-stream, there is reason to believe that while the Yazoo swamp return flow is controlling the fall between Lake Providence and Vicksburg, the local slope at Hays' Landing will depend much more closely on the average slope above than on that below. Therefore, since there was no time in 1882 when the two falls from Greenville to Lake Providence and from Lake Providence to Vicksburg were each equal to those falls on April 7, 1883, we must take the date in 1882 when the fall from Greenville to Lake Providence was most nearly equal to the same fall on April 7, 1803.
In 1882 tho Greenville gauge record is missing from April 9 to April 22 inclusive, but as far as can be judged by the general form of the curve, and from a comparison of it with that of Arkansas City, the fall between Greenville and Lake Providence in the river surface, between February 1, 1882, and June 25, 1882, had no value less than 20.98 feet, which was reached on May 6, 1872. On that day the fall from Lake Providence to Vicksburg was 14.43 feet. From these data it is seen that at no time between February 1 and June 25, 1892, was the average slope between Greenville and Lake Providence as small as on April 7, 1883; that its minimum value in the overflow