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The territory covered by the general survey work was projected on two charts, Nos. XIII and XIV, continuous and uniform with those preceding them, on a scale of 1 inch equals 1,000 feet, and are at this date about eight-tenths complete in pencil. Further details regarding these surveys are given in the report of Mr. A. H. Blaisdell, assistant engineer, Appendix A.

Special surveys were made by Assistant Engineers S. W. Fox and S. H. Yonge at the various localities at which works of improvement were projected, and in addition many instrumental observations and surveys for the study of conditions and effects as the works were being carried on.

Examinations of present state of the works of improvement placed in previous years were also made and reported upon by these assistants.

On the Osage River bench marks were established at the head and foot of each shoal as far up the river as Warsaw, 171 miles, to which the extreme low water of the year was referred.

Examinations also were made on the Osage and Gasconade rivers and are referred to under those headings.

Mapping charts I to XII, inclusive, of the general topographical map of the Missouri Valley, from the mouth to Lexington, Mo., 322 miles, on a scale of 1 inch to 1,000 feet, are now complete in ink.

A general map of the Osage River from the mouth to Osceola, 228 miles, on a scale of 1 inch equals 2 miles, was compiled from former surveys and other sources, showing the characteristic features of the country commercially tributary to the river, the water shed, etc.

The maps of the survey of 1895 on the Gasconade River above Vienna, a river distance of 29 miles, were completely inked and a general map of the river, on a small scale, covering the entire surveyed distance of 109 miles, was prepared.

GAUGES AND PHYSICAL DATA.

On the Missouri River 22 permanent water gauges were maintained throughout the year independently of those maintained in connection with works of improvement, their records being reported weekly to this office.

Through the courtesy of the engineer officer in charge of the river above Sioux City, the weekly records of the gauges at Bismarck, N. Dak., and Townsend, Mont., were also furnished.

Hydrographs of all the gauges were kept platted to date and any errors made manifest were at once traced and corrected.

There were but few inexpensive repairs needed on any of the gauges during the year, but two of the inclined wooden gauges, of which there are but five now in use, will require renewals or extensive repairs after the water has reached a lower stage.

During the fall one inspection trip was made and one again during the spring.

The assistant making these trips, in addition to the inspection of gauges, was charged with other duties, such as the collection of commercial statistics, the inspection and measurement of bridges, and other work requiring the services of an engineer.

Of the 12 pilot bulletins maintained between the mouth and Kansas City, the one at Kansas City was continued throughout the entire year at the written request of local steamboat interests, but the others were discontinued during the months of December, January, February, and March.

All the bulletins read from a stage 5 feet below standard low water, and dating from January 1, 1898, when the United States Weather Bureau lowered the zero elevation of their Hermann gauge to 68.2 feet above the St. Louis directrix, the bulletin readings practically correspond with the published records of the Weather Bureau.

The four permanent gauges on the Osage and the one on the Gasconade were continued without interruption. For further details regarding the gauges see report of Assistant Engineer A. H. Blaisdell, Appendix B.

Assistant Engineer J. A. Seddon, in connection with his work of physical data investigation, has made a special study of the formation of the floods of the Mississippi River and tributaries, and the effects of reservoir systems on stream flow.

CONSTRUCTION.

NEBRASKA CITY, NEBR.

At the close of the last fiscal year, one of the three riprap aprons projected for the protection of Nebraska City front had been completed. The other two were completed July 10.

These aprons are 50 feet in width, separated by spaces, beginning with the upper one of 150 feet and 100 feet respectively.

In April, 1898, the caving extended lower down, and it became necessary to protect 236 linear feet of bank adjacent to and below the lower apron by a similar riprap.

The bank is fine sand overlying very hard material, probably blue clay, at a depth of 25 to 35 feet.

The riprap below water was made from 2 to 3 feet in thickness with its outer face on a slope of 1 on 14; above water the bank was graded to a slope of 1 on 1 and covered to a depth of about 8 inches.

DIKE CONSTRUCTION.

Under a project approved by the Chief of Engineers September 21, 1897, it was proposed to build three pile dikes to ameliorate a condition of flow which at certain stages menaced the safety of the United States revetment on the left bank built in 1889 and 1890, and at others was causing caving on the Nebraska City front. The dikes were to have curved ends, by which it was expected that the flow would be eased about their ends, making less eddy and causing the accretions to form nearer to the channel line, and also that heavy drift would not accumulate against them.

The project was completed as far as the construction of two dikes, numbered 3 and 5. The other dike was found unnecessary. Dike No. 3 was built between November 5 and 23, and is an extension to stub dike No. 3, constructed in May, 1897. It is in the form of a circular arc, 400 feet in length, with a radius of about 340 feet.

Dike No. 5 was commenced March 16, and with exception of the screening was completed April 6. The screening was attached gradually after completion. The dike is formed of 80 pile bents, 37 of which extend from the shore about normal to the flow, and the remaining 43 bents from the curved trail made as a circular arc of 340 feet radius. Its projection on a normal to the standard high-water contour is about 725 feet.

Driftwood, which usually accumulates in such quantities as to imperil

the safety of, if it does not cause a breach in dikes normal to the current, has found but little lodgment on Dike No. 5, and Dike No. 3 has been entirely free from it.

Soon after the completion of Dike No. 5 there were several sharp rises which caused extensive accretions to form under both dikes, and although the higher stages of June did not submerge them, the amount of accretions have been quite satisfactory and are of a height nearly equal to that of the maximum stage.

OPPOSITE LEAVENWORTH.

Under a project approved by the Chief of Engineers June 5, 1897, it was proposed to build a system of three dikes on the Missouri side of the river above the Fort Leavenworth Railroad Bridge to prevent further erosion of the point at the foot of the bend and to restore, as nearly as might be, the channel line in front of the landing at Fort Leavenworth to the position it occupied in 1890.

It was also proposed to repair an 80-foot breach in Dike No. 1, between the bridges at Leavenworth and at Fort Leavenworth, built in 1895. The latter was accomplished between July 22 and August 4.

The system of three dikes was built, but its location was moved slightly upstream from that first intended.

Each of the three dikes had placed above it a sheer dike consisting of clusters of three piles spaced 25 feet apart, to ward off and prevent accumulation of drift and floating ice against the main dikes.

Construction was carried on during August and September. All the dikes were built into or across the deep water of the main channel of the river and much difficulty was experienced from bottom scour which would set in after the piles were driven and before the foot mat was sunk. Great care was, therefore, taken to make the dikes more than ordinarily strong, and the bracing of the structure was done in a most efficient manner.

A number of special devices for accomplishing cheaply certain portions of the work were very effective and ingenious.

An inspection of the dikes made in May showed a considerable amount of accretions as a result of the April rise, but no survey to determine present conditions can be made until the present high stage subsides.

For details of the work see report of Assistant Engineer S. H. Yonge, Appendix D.

LOCAL WORKS BELOW KANSAS CITY, MO.

The work of the year embraced training and protection works in the form of dikes and bank heads, or bank heads alone at five localities. The extreme upper location was 334 miles from the extreme lower one. The work was carried on under a general allotment of $94,000 in accordance with the projects approved by the Chief of Engineers August 6, 1897, with suballotment for each place as follows:

Near mouth of Little Blue....

At Miami....

Above Glasgow

Near Rocheport.....

At Howards Bend above St. Charles..

$20,000 22, 000 20,000

13, 000

19, 000

Subsequently the allotment was increased $5,000 by transfer from anotber allotment, as previously stated.

The form of pile dikes as they were constructed last year with improved bracing and wire strand ties remained unchanged, except that cottonwood piles and lumber were largely used.

In the construction of the bank heads a radical change was made from the experimental one of last year in Chamois Bend. In those built this year no encroachment on the stream was made with pile work, but nearly the entire structure was built into and masked by the bank.

It was considered that until it became uncovered by scour its effect on the flow would be gradual, permitting the river to accommodate itself to the restraint without producing any violent changes in regimen. The general plan decided on was as follows:

A circular arc of 350 feet radius, in the plane of standard low water placed tangent to the bank, defines the level and inner edge of a floor on which is piled loose stone 5 feet in height and of sufficient width to contain 125 cubic feet per linear foot in its upstream arm, and a quantity gradually diminishing to 12.5 cubic feet per linear foot at the end of its lower arm. This circular arc is known as the post circle, being marked by posts, and the radius to the point where the section of the stone begins to diminish as the directrix.

Central angles of 60° above the directrix and 40° below, mark generally the extremities of respective arms.

From the floor of the post circle an earth slope covered with stone rises 4 feet on a slope of 1 on 1 to a berm 4 feet wide, from which a slope of 1 on 2 is carried to the natural surface of the ground. The berm and upper slope are paved.

All the bankheads, except the upper one above Glasgow and the one near Rocheport, corresponded as closely in construction with this specification as circumstances permitted, and experience appears to indicate that the closer the correspondence the better were the results.

In the earlier part of the work there was a failure on the part of contractors to deliver stone at the times specified, and much of the work had to be performed late in season during unfavorable weather at largely increased cost.

NEAR MOUTH OF LITTLE BLUE.

Dike 1 A.-This dike, closing Independence Chute, was built during September, but in February heavy reinforcement was placed at both ends to prevent undermining and flanking. A large field of drift is now lodged above it, the flow is practically cut off, and a large fill exists below.

Dike 2 A.-The original project included the construction of this dike on the north side of the river in Clay County, and part of the material was gathered and stored near its site. The water along the north bank shoaled so much, however, that it was inaccessible to floating plant, and later the scarcity of funds compelled a postponement of its construction.

Bankhead 3 A.-This was built according to the general plan. There has been persistent erosion, both above and below the bankhead, which has been not only uncovered, but the paved slope for 90 feet up from its lower end has disappeared. This would seem to indicate that the diminished section of stone in the lower arm of the structure was insufficient to protect the slope as the scour continued, and points to the necessity of keeping the full section of stone around the entire length

of the arcs to meet all conditions of flow. Some short temporary spurs of brush and stone have been hastily placed to prevent further erosion during the high-water stage.

The stage of water has been too high to admit of detailed examination being made.

At Miami, Dike 1 B.-This dike, designed to be 1,800 feet in length, was built across a left-hand channel chute to form a single channel toward the right bank. At the close of operations November 13, 1,500 feet of it had been built. On December 8, an examination disclosed that a heavy mass of ice had accumulated against the dike, diverting the greater part of the flow into the old channel way across which the dike was built and scour had loosened a few piles.

Reinforcement was at once made, and during the second week in March the curtain was repaired and replaced where necessary.

Bankhead 1 B.-This bankhead was built in accordance with the general plan, but with a central angle of 90°, of which 50° were above the directrix.

A large bar now exists above and below the dike, and the right-hand chute, which passes the bankhead and into which the main flow is to be directed, now carries probably half the discharge. A better result would doubtless have obtained had it been possible to carry the dike to its projected length, which will probably be accomplished during the coming season. Both dike and bankhead are now submerged, and the latter has been uncovered by the erosion, but details of conditions must await a survey at a lower stage of water.

ABOVE GLASGOW.

Three bankheads were built in Wilhoites Bend, designated successively 4 C, 5 C, and 6 C, on which work was begun in November. On December 1, when floating ice closed the river to navigation, 6 C had been completed, 5 C was nearing completion, and practically only the earth excavation at 4 C had been finished. It was not possible to barge any more stone from the quarry landing, and a small quantity which had been delivered at 4 C was used in completing 5 C. A temporary change of direction in flow due to ice action produced rapid caving at the site of 4 C, which continued until it had reached the top of the graded slope at the directrix.

The completion of the bankhead was undertaken in March, and as there had been but little change in bank line it was decided to utilize the damaged trench as far as possible and build the bankhead under a modified form. On each side of the directrix, where the original earth slope had been destroyed, the slope was restored by an earth fill supported on a toe of rock. A wall was then massed in a section of about 150 square feet to a height of 5 feet above standard low water at the directrix, and gradually rose to 12 feet above where it entered the bank and to 15 feet above at the ends of the bankhead.

Bankhead 5 C was built in entire accordance with the original plan, as was also 6 C, except that the central angle of its lower arm was stopped at 30° below the directrix. An examination of these bankheads, made June 17, 1898, showed them standing well and in good condition after a particularly severe attack. Bankhead 4 C was in dead water and covered with mud, and in bankheads 5 C and 6 C the outer walls had nowhere receded to the post circles.

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