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SUMMARY

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The revetment work now in existence at Plum Point Reach covers a total length of about 64,000 feet. Of this some 3,200 feet is in poor condition, 6,000 feet in fair condition only, and 54,800 feet in good condition. Of the latter, 31,600 feet have been put in since 1893 with fascine mattresses and 22,600 feet consists of older work with woven mattresses. The total cost of the work has been about $2,400,000.

Memphis Harbor (from 227 to 233 miles below Cairo).-In Memphis Harbor bank revetment has been constructed at two localities, in Hopefield Bend, on the right bank, and along the Memphis city front, on the left bank.

Hopefield Bend. A complete description of the revetment of this bend from 1882, when the work was begun, to and including the work of the season of 1892, has been previously given. (See pages 133 to 162. At the end of this period the revetment extended from Mound City Chute to Hopefield Point, a distance of about 16,600 feet. The upper 6,300 feet of this work was protected by an outlying sand bar, and the bank along it was not caving, although the upper bank revetment was practically disintegrated and the subaqueous mats were of less size and strength than later experience had shown to be necessary. The lower portion, about 10,300 feet long, had been covered with much wider and stronger subaqueous mats and had had the upper bank along them paved with stone, but owing to the strong current this revetment had failed frequently and nearly all of it had been renewed at least once. All of the mats used along this portion of the bank had been of the standard diagonal, woven type, and as experience had shown that this type could not be relied upon under all conditions the thicker and stronger type of fascine mattress was evolved, and in all of the work at this place since 1892 this new type of mattress has been employed.

SEASON OF 1893 As has already been described (page 158), two extensive breaks occurred along the lower part of the revetment during the spring flood. These breaks were along the revetment built in 1888 and involved practically the complete destruction of all that remained of that season's work.

One break was located just above the subaqueous mattress placed in 1892 and extended upstream to the foot of the repair work of

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4) a distance of about 2,000 feet. Along this stretch the bank ering

had been almost entirely destroyed by the caving, and at - lower end of this break a large hole had been washed out back å the paving. This hole extended for about 250 feet along the sney mattress, was at one place 100 feet inshore from the low-water catour, and at its deepest part was 3 feet below water. A part

the pared bank in the shape of a projecting ridge inclining upram was thus left between the hole and the river. The other break was located just below the 1892 mattress, near tje head of the railroad incline, and was about 500 feet long and kod destroyed the entire revetment, both subaqueous and upper bank. Between this break and the point proper, a distance of about uw feet, signs of weakness were in evidence along the revetment which was a portion of the 1888 work. The point itself had during the high water been moved upstream about 90 feet by the eddy

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The project for the season's work was to completely revet both breaks, employing wide fascine mats; to repair the hole along the bead of the 1892 work, and to extend the mattress of the lower brak down to and around Hopefield Point. (Plate L.)

The work was begun September 1 and completed December 1. Three subaqueous mats, 310 feet wide and covering 2,014 linear ftet of bank, were placed along the upper break, and one subaquevas mat, 916 feet long by 310 feet wide, was sunk along the lower break and extended to Hopefield Point, which was now 339 feet short of its location in 1888. The loss being occasioned by the eddy under the point scouring up and behind the work. The subaqueous mats protected 2,930 linear feet.

Connecting mats, also of the fascine type, were placed in pockets and where the subaqueous mats did not come close to the bank and were lapped over the latter from 10 to 30 feet. These connecting mats were from 20 to 150 feet wide and were placed along 2,175 feet of bank. The upper bank was graded to near its top to a slope of 1 on 3, leaving a shoulder there of from 4 to 6 feet high, usually of compact clay. The paving extended to between the 26 and 30 foot stage and was made of 31/2 inches of crushed stone and 61/2 inches of riprap, packed close; 3,066 linear feet of bank were thus pared. In addition to the paving, 1,855 cubic yards of stone were placed on old work near and along the low-water line, thus reinforcing 6,911 square yards of old revetment. The total cost of the season's work was $100,000.

SEASON OF 1894

No damage was done by the high water of this year. In the autumn the river fell to quite a low stage and exposed considerable of the mattresses, on which the ballast had been placed by casting it in the water, and it was, consequently, not uniformly distributed; the it was also insufficient to cover all the exposed mats, so about 2,400 cubic yards of stone were added, and the mats were paved down to the low-water line, 5,800 linear feet of the work being so treated. A fascine connecting mat with an area of ninety squares was sunk along the 1890 work, where the old brush work was broken up, being badly decayed, and a slight undermining of the bank was in progress.

The high waters of 1895 and 1896 caused no damage to this work, and no work was done during those seasons.

SEASON OF 1897

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In the spring of this year there was a phenomenal high water at

Pop this locality, the stage being 2 feet above its previous maximum, the increase in flood height being due largely to the levees which had been recently built along the St. Francis front above, these levees holding the water in the channel, which heretofore had escaped over the bank. The increased flood height produced notably *** higher velocities, especially along the upper bank, and scoured the unrevetted portions above the paving at numerous places.

At six places holes were washed out back of the paving. One of these was scoured to a depth of 3 feet below the zero stage, destroying most of the paving and involving the shore edge of the subaqueous mattress for some distance. This hole also extended for s'an some distance into the high bank. The other holes were of lesser extent, none being cut to below the 12-foot stage, or from 12 to 16 a les feet below the original top edge of the paving. These holes also extended for some distance into the high bank, and the upper por- ja as tion of the paved slope in front of them was broken down, the stone from which had slid into the holes. At many other places the bluff: The bank at the top of the paved slope had been scoured back for some DS distance, leaving nearly level bench (often 20 or more feet wide) between it and the top of the paving.

The work of the season consisted in building spur dikes across the six washout holes, not only with the object of preventing future caving by checking the current, but with the expectation of causing thed.

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deposit between these spurs and thus to some extent restoring the original grade of the bank. These spur dikes were in general built arross the middle of the holes, extending from the top of the existing paving to the top of the bank behind, with their crest slopes on straight line connecting the two. Seven spur dikes in all were built; five of these were founded on sill mats of the fascine type, but the other two, being small, had no sill mats. Along the large hole a fascine subaqueous mat 280 feet long by 110 feet wide was sunk, together with a connecting mat 100 feet long by 54 feet wide. Another small connecting mat was placed in front of a minor break which had occurred near the low-water line at another locality. Considerable paving was also laid along the edges of the washout hole.

SEASON OF 1898 The high water in the spring of 1898 reached very nearly the stage of the preceding year, but the dikes then built along the upper bank were quite effective in preventing further caving, althoug! the holes enlarged slightly at the ends, and but little deposit was formed by the dikes. Additional bank scour, however, occurrel along the unprotected portions, the bench above the paving being increased in width at a number of places, but at no place was it scoured to below the level of the top of the paving. Other damage to the work was confined principally to breaks along the low-water line and where the subaqueous mats were of the old or woven type. The largest break was near the lower end of the 1891 revetment and immediately below a salient where there was a strong eddy current. The length of this break was nearly 300 feet, measured along the low-water line. The scour into the bank involved all of the paved slope, and along the former low-water contour there was a maximum of 30-foot depth at zero stage. Probings disclosed the presence of the subaqueous mat, except along the inshore edge, where for some disance it had no doubt been broken up and washed away. The break was repaired by sinking across it a fascine mat, wide enough to lap the old mattress where it was thought to be in good condition. The mat built was 300 feet long and 100 feet maximum width. The inshore edge was well cribbed up to prevent buckling, as the slope on which it was placed was unusually steep. The upper bank was graded and paved up to the 23-foot stage. The only other break involving the subaqueous mat, and this but slightly, was also in the 1891 revetment and about 400 feet below the break just described. This break was about 100 feet long and had cut

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into the bank far enough to destroy about half of the paved slope The repairs consisted of a connecting mat 120 feet long by 50 fee wide and restoring the upper bank paving.

The other failures were longitudinal faults in the paved bank just above the low-water line, caused by the settling of the sub.. aqueous work. These faults were 2 or more feet in vertical height; one of them was opposite the head of the railroad incline and was about 100 feet long. It was repaired with a connecting mat 100 feet long by 21 feet wide, removing the paving along it, grading : down the bank, and replacing the paving with some additional stone. Similar faults occurred just above the extreme lower end of the revetment. They covered a length of 300 feet of bank and were repaired in the same manner as the one just described, except that no mattresses were used. The fault at the head of the incline was along the 1892 revetment, and the others along that of 1893 and due to a failure to connect well with the shore work.

SEASON OF 1899

The high water of 1899 was of only moderate proportions and did only minor injury to the revetment, consisting of slight faults near the low-water line, caused by the continued settling of the old subaqueous mats and a small amount of scour above the paving.

The successive failures in the old-style work led to a project to cover it with fascine mats, especially along such portions which had to resist currents of very high velocities. There were two sections which badly needed reinforcing; one was the interval between the 1893 mats, about 1,400 feet in length; the other was above the upper end of these mats, having a length of about 1,900 feet, and along which faults had occurred during previous high waters. Under an allotment of $60,000 made this year this work was done. One mat covering 1,415 feet of bank, 250 feet wide, was placed along the interval between the 1893 mats, and two mats, 250 feet wide and covering 1,850 linear feet of bank, were placed nest above the 1893 work. The total length of bank covered with fascine mats this season was 3,265 feet. Six connecting mats, aggregating 1,036 squares, were placed, two along the lower section and four along the upper section, one of the latter being along the large pocket repaired in 1898, the mat in which had slid a short distance down the slope, owing to its steepness near shore. Paving was done along exposed places near the low-water line, and along the top where it needed extension, and at some other localities; the total laid being

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