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sunk, the process takes time, and every lot of drift sunk sortu
crease the pressure on the other parts of the dike, and as an
the dike would sometimes break during this process. Only
however, the raft soon silted up and not only acted as a pro-
to the dike, but as an effectual closing of the chute.

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INSUFFICIENT PROTECTION AGAINST SCOUR

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This is responsible for more failures than any other one The protection first used was a narrow mat placed in front : dike after its construction. These mats were of insufficient : even if properly placed, to protect the piles against long contin erosion, as they would be undermined along the outer ride finally slide down and away from the piles. Great care was to so sink these mats that they should lie snug against the to the dike, but this could not always be accomplished, and then have been in some cases several feet of bare bottom between the and the piles. At first no provision against scour between t ing was made, but later a form of grillage mat was woven and between the rows composing the dike. As already stated, it necessary, in order to insure proper sinking, to leave liberal y around the piles or clusters and these openings invited at Then, again, in strong currents piles or clusters could not al be driven in a perpendicular position, but would spread outs even when good sized openings were left in the mat, opening on the water surface appeared to be amply large, the mats not lie flat on the bottom by reason of binding against the near the bottom, and instead of preventing scour, the grillar times increased it. Again, where drift had accumulated in : of the dike, the mats could not be given that extension upstrea necessary to insure lapping over the previously sunk foot! Neither could mats constructed as these were be given sufficient tension downstream to protect against erosion from the overi It was found that erosion is more active just in rear of the d. than in front, especially if much of a head be formed. Wh thick mass of drift is collected in front of a dike, the current deflected downward, and unless the base and rear are well y: tected damage to the structure at some place is inevitable, and wt the dike is once gapped, be the gap ever so small, destruction go on rapidly from both ends of the gap. At some dikes the cumulated drift had a thickness in the immediate front of 18 ! Such a thick and dense raft would cause a strong downward der

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akes time, and every la

on the other parts of the netimes break during this

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on silted

and not

and this increment to the scour would soon reduce penetration n, such an extent that the piles would give way. Fifty feet beyond

dike the water usually shoals rapidly, indicating that the en1 effectual closing of ter of the work and that an apron extending about that distance in

of the current had been expended at or in the immediate vicinзу ar would protect against erosion. In Bullerton Cross Dike No. 2. id the repairs to Bullerton No. 1, where wide mats were laid be

re pile driving, and each dike had a good apron extending beyond ord was a narrow me te par row, no scouring out of piles took place, although thick tion. These mats Wer ift rafts formed in their front.

CIENT PROTECTION AGLK

for more failures than

to protect the piles sze: be undermined alone

LACK OF DURABILITY OF MATERIAL

s and these openings

away from the piles. in It was hoped when this dike work was begun that the dike would at they should lie sake quickly silted up and that once covered by silt they would be ot always be accompi, apt always wet and, therefore, be preserved from rotting, at least everal feet of hare better a considerable time. Both of these expectations were doomed

provision against se, » disappointment. The dikes did not rapidly silt up, the fills being form of grillage mat x-reater above and below the dikes than at them, and even when ng the dike. As alm-ilted up the decay above the low-water line was not prevented. e proper sinking, te la short life of the timber used for piling was subsequently in part

liminated by the substitution of cypress for the willow and cottonrents piles or clusten, vood previously used. Preference had been given to willow and - position, but would , ottonwood on account of the plentiful supply of these timbers adgs were left in the mat

acent to the works and their consequent cheapness, but when it --d to be amply lare, was found that the life of such piling was not sufficiently long to reason of binding agai

nsure permanent results cypress was substituted. While this latof preventing scour •

ter lasts much longer than the former, it still does not fill the relere drift had accum, quirements of standing sufficiently long to insure beyond a doubt be given that extensis

the results desired from closure works. Such a structure as a dike er the previously sue

in the river, even when silted up, is subject above low water to con

ditions that in time will impair the soundness and strength of the as these were be givene

best of materials, being alternately exposed to submergence and to against erosion from 1 re aetive just in mo, atmospheric influence, and while cypress resists this action longer

than the other woods mentioned, still its life under such conditions i of a head be formel

does not exceed five years, which period is rather too short to insure n front of a dike, the

good results from the dikes at all locations. Trouble from this dethe base and rear af

caying timber is, of course, one that increased as time went on. It ome place is inevitable i

was just beginning at this stage in the history of the dikes and was I ever so small, destra

to become more important in the future. he gap. At some dit

One other fault that underlay these experiments at river conthe immediate front ..

traction, especially as regards Gold Dust Chute, was the attempt to use a strong downwar

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Such a resu

cal

do too much at once. To close at one stroke this chute with its lar:
cross section and a high-water discharge of nearly half a mila
cubic feet per second was almost superhuman. Such a subi:
change in the regimen of the river must necessarily cause maitza
forces that were practically irresistible. As stated above, alle
dike work above Cross Dike No. 4 could better have been omit-
and the result better obtained by one or two additional like
farther down the chute. The dikes, it is believed, should not hesia
been built higher than the 10-foot stage, except near the banka
With such low dikes trouble from drift would have been much limi
ened, and strength and durability would have been increased at
these dikes would probably in a few years have caused deposits that
would have closed the chute to about this stage.
would have accomplished the main object of the work; that in
keeping the entire lou-water discharge in the main river, and it
desirable, new structures resting, as a foundation, upon these da
posits could have been constructed to cause still further closing a
the chute.

This same fault, haste, was the cause of much loss throughout ttdike work above described and also in the revetment work to bu mentioned hereafter. The piles of the dikes were driven far abra of the ability of the mat party to keep up with the work, and me construction was pushed far ahead of the supply of stone to sit: them. As a result, dikes were frequently caught by high wat: without mattress protection, and mats were caught by the rise floating and with no means of sinking them. The latter wou probably be destroyed and the former scoured out.

As another example of the same haste, the attempt seems to have been made, at least in the early stages, to carry on the work regar) less of the stage of river or the presence of drift. In some casi mats were left floating after the bars or dikes along which the were to lie were entirely submerged. The result of all this was di only that the working parties were seriously hampered by the strong currents and large amount of drift due to these high stage but a large amount of partially finished work was destroyed, an the cost of the improvement enormously increased.

The cost of this dike work up to March, 1885, was about as fo lows: Gold Dust system, $640,000; Osceola-Bullerton system. $510,000; Plum Point system, $370,000; total, $1,520,000.

This, with the $690,000 expended in the same time by revettin. banks, makes a total of about $2,200,000 as the cost of the Plur.

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Point work up to this date, and yet some work was still needed on the dike system, and the bank revetment was not over one-quarter completed.

The original estimate of cost of the Plum Point work has been Id better $736,000, it being stated, however, in making this estimate:

“It is believed that such additional works, as will ultimately be is believe required to complete and render permanent the improvement con

templated in the system at the localities specified, will not exceed the amount herewith stated as needed for actual work." That is, that the total cost of construction and maintenance of the works in Plum Point Reach would not exceed twice $736,000, or approximately one and a half million dollars. This estimate and the actual cost and result of the first works constructed make an interesting comparison and show how greatly the character and cost of work on this river had been underestimated.

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foundation, use still furi

CONTRACTION WORKS, 1885-1892

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season.

The foregoing account of the dike work at Plum Point Reach was the revetu-carried up to the end of the season of 1884.

The high water of 1885 tore several gaps in the works, one each

in Bullerton Cross Dike No. 1 and Plum Point Cross Dikes Nos, 5 e supply of:. and 6 and two gaps in the main Gold Dust dikes below the inter

section with Cross Dike No. 2. These latter two gaps, with the un

closed openings in Cross Dikes Nos. 3, 4, and 5, left an unobstructed hem. The passage through Gold Dust Chute, which was, of course, deeply

scoured.

There being no funds available, no repair work was done this rry on the we

The high water of 1886 did still further damage. An additional likes along a gap was made in the main Gold Dust Dike. A large part of Osceola esult of all th: Cross Dike No. 3 was torn away, and the wreckage and drift from it sly hampera tore a large gap in Cross Dike No. 4 of that system, while other le to these hig' damage was done to this latter dike near its outer end. The cause rk was desta of all these breaks was deficiency in strength due to decay and to reased. other minor damage previously done and not repaired. 385, was alwa During the latter part of the season a small amount of money bela-Bullerton came available, and some slight repairs were made to the outer end 1. $1.520. of Osceola Cross Dike No. 4 and to the lower dike of the Plum Point me time by r system. Bullerton Cross Dike No. 2 had given some evidence of he cost of the weakness, and this dike being considered of great importance, a

of drift. lns:

small additional allotment was obtained for repairing it. The team rial was purchased and delivered, and work was just about to begin when the dike gave way and was so severely damaged that its repair became a work far in excess of the available funds, and nothing was done.

d

SEASON OF 1887

The principal damage done by the high water of this season was a gap in Osceola Dike No. 1. Later in the season, during low water a brush fire was communicated to Osceola Cross Dike No. 4, and; large part of the superstructure was destroyed by fire.

During the season no work was done.

SEASON OF 1888

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This high water also did some damage to the dikes, especially at Gold Dust, where the gaps in the three lower cross dikes when widened greatly.

It is thus seen that since the stoppage of work at the end of the season of 1884, four high waters had come and each had left its marks upon the dike system, while during this time practically w work of repair had been done. Gaps now existed completes through all the chutes; Gold Dust ; Osceola, behind both bars ; at Bullerton; and as much damage had also been done, as we shai afterwards see, to the bank revetment, it is evident that this four years' delay occurred at a most critical time, and had resulted ir well-nigh wiping out all that had previously been done.

And yet, in spite of all the damage to them, the dikes had hal large results. The survey of 1888 (Plate LIX) showed that around the Plum Point system the bar had grown up to above the 25-fow stage out to near the end of the five upper cross dikes and that the low-water line practically followed the ends of these dikes.

At Osceola Bar both the upper and lower entrances to the chuthad been made out to the general bar line, and the chute behind the upper bar was closed at about the 25-foot stage, and behind the lower at the 17-foot stage. The entrance between Osceola av: Bullerton bars had narrowed a great deal and was now closed at the 3-foot stage. The chute behind Bullerton had also narrowed a good deal and was closed at both ends at the 3-foot stage.

At Gold Dust also large deposits had been made; the triang formed by the main dike and Cross Dike No. 2 had filled up fairly solid to near the 20-foot stage, and below the triangle there was a

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