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at about 600,000 cubic feet per second, so the margin of safety appears ample.
Except between the latitudes of Simmesport and Melville where the levee on the east bank protects the upper part of the Pointe Coupee Parish and has been raised to confining grade; the Atchafalaya River levees are maintained at existing height, which is below the grade of the floodway guide levees. This permits interchange of flow between the two floodways, and the river, in the event that either should become overloaded.
Water is to enter the west Atchafalaya floodway by overtopping and crevassing the so-called fuse-plug levee at its head. This levee is to be maintained at 1914 grade and 1928 cross section. It is already practically to that grade, and it is planned to bring it to full crosssectional dimensions this coming year.
It is planned to construct a control structure similar to that at Bonnet Carre at the head of the Morganza floodway, supplemented perhaps with a fuse-plug section to be breached in case the control structure proves unable to admit flow to the floodway's full capacity. The frequency of operation will depend upon a number of factors, including the amount of silting evidenced in its first operationwhich is still to be experienced. If silting is slight it will probably be used to reduce operation of Bonnet Carre where sedimentation has proved to be heavy.
The floodway guide levees above Berwick and Morgan City are completed except for closure of various gaps left for convenience of navigation, roads, and railroads, and for adjustment of grades involving increases of about 1 foot between Viva and Ramah, 26 miles on the east levee and between Courtableau and Catahoula, 49 miles on the west levee; levee enlargement by placement of second and third lifts on levees where soft foundation and poor material have necessitated this method of construction between Ramah and Morgan City (60 miles) on the east, and Catahoula and Berwick floodgate (58 miles) on the west. These levees range from about 1 foot to 5 feet below grade. About 231,2 miles of grade raising and second-lift work are already under contract and it is planned to complete all of this work next year, insofar as foundations and physical limitations of the material will permit.
The east guide levee crosses the Plaquemine-Morgan City route of the Intracoastal Canal. A lock is planned at Bayou Sorrel. It has been offered to bidders and should be under construction very shortly. In the meantime, traffic has used a gap in the east guide levee at Bayou Sorrel, which has been a source of much trouble. When the Atchafalaya River overflows its banks, water enters the basin east of the guide levee through the gap and pressure is exerted by those living there to have it closed. Navigation on the other hand is interested in having it remain open because after it is closed vessels have to go about 150 miles farther (via Harvey lock and New Orleans) to reach ports north of Plaquemine, and have to contend with the swift Mississippi River currents all the way from New Orleans.
The traffic over the Plaquemine-Morgan City route amounted last calendar year to about 1,161,000 tons even with the route closed for about 5 months, and the year before to some 2,358,000 tons. The cost of moving that much commerce 150 miles farther, with 110 miles of
the added distance against a Mississippi River current, is considerable, and while one's sympathies may be with the small farmers and merchants whose way of life is disrupted by the water, and the natural inclination is to close the gap when even moderate flooding is in prospect, it has to be recognized that the navigation interests have equal rights. The problem is further complicated by the fact, not appreciated by many of the people affected, that below the latitude of Napoleonville or Pierre Part, the flooding is due in the main to backwater occasioned by high stages at Morgan City, induced or increased oftentimes by high wind tides and heavy rainfall. Closure of the gap for ordinary floods such as that of this year would not greatly affect stages in this area, where the bulk of the damage and discomfort occurs, as was evidenced last year, when closure (in the face of much higher predicted stages than have been in prospect this year) failed to afford relief below Pierre Part.
It cannot, of course, be alleged that it is desirable to have an opening in the levee, nor that closing it is not desirable. I am merely trying to point out that in the present instance the relief (with stages in prospect this year) would be entirely incommensurate with the expense and inconvenience occasioned navigation, and it became my unwelcome obligation to recommend accordingly.
We have advertised the Bayou Sorrel lock for contract but it will take at least 2 years to build it and the Bayou Pigeon Gap cannot be closed without disrupting navigation until the lock is ready, unless an alternate route to the east of the guide levee is made available. It fortunately appears that in connection with our plans for work below Morgan City the provision of such an alternate route can be justified.
The manner of extending the Atchafalaya floodway levees below Morgan City and Barwick has been under study for a long time. A number of alternatives were investigated, each having its own advantages and draw-backs. It has finally been determined that the east levee should cross Bayou Boeuf just east of Morgan City, follow down the western shore of Avoca Island, cross Bayou Penchant, and continue to the lower end of Sweet Bay Lake. This obviously will require either a lock in Bayou Boeuf at Morgan City or a rerouting of the Intracoastal Canal. The latter appears to be preferable, hence it is planned to continue the route south from the present route beginning at mile 70 west of Harvey lock by a new cut reaching the Atchafalaya at the end of the proposed east Atchafala ya Basin levee. An added feature is a cut from the end of the proposed levee to Bayou Chene and improvement of Bayou Chene to compensate for the interruption of southward-flowing drainage entailed in closing Bayou Boeuf and Penchant by the east levee. The cut will incidentally provide a protected route to Morgan City from the modified Gulf-Intracoastal Waterway.
It is tentatively planned to place a floodgate in Bayou Boeuf at Morgan City. It is also planned to provide an alternate, slackwater route, for the Plaquemine-Morgan City sector of the canal by dredging a channel along the shore of Lake Palourde and performing such operations in Bayou Milhomme and other streams as are necessary to secure a workable alinement and 12-foot depths in the natural water courses above the lake. The cost of providing the
Pic City railroad bhe lower Atcha la stages the
alternate route is about $950,000. It will obviate at high stages the difficult and somewhat dangerous trip up the lower Atcha falaya River and through the Morgan City railroad bridge—and will permit the closure of the Bayou Pigeon gap without forcing commerce to go materially out of its way. It is not planned to alter the highway and railroad bridges over Bayou Boeuf although their horizontal clearances—66.0 and 54.5 feet, respectively—are less than standard for the main Intracoastal. The plan ás now conceived should adequately protect not only the Morgan City area and the lands below Pierre Part, now inundated by backwater, but the territory to the east near Houma as well.
On the west side it is planned to carry the levee line to the present Intracoastal Canal and along it to the spoil bank levee of the Wax Lake outlet, with a drainage canal running to the vicinity of Patterson for the evacuation of drainage from the leveed area between Berwick and Wax Lake outlet. The lowlands between the canal levee and the Teche Ridge should, it is believed, provide adequate sump storage facilities. If further study shows that they will not, it may be found desirable to extend the levees southward, closing the present Intracoastal Canal, or to provide pumping facilities. To provide adequately for navigation to Patterson which is a large shrimp-packing center, the plan includes the provision of a lock in the lower Atchafalaya River north of Berwick. This will furnish access to the shrimping fleet and other commerce at all times.
Considerable flooding has occurred between the Wax Lake outlet and the Bayou Sale Ridge and navigation has had trouble crossing the Wax Lake outlet when it was discharging floodwaters from the Atchafalaya Basin. For these reasons, and to avoid a difficult upstream trip against rapid currents in the lower Atchafalaya River for vessels traveling west on the Intracoastal Canal after it has been relocated east of the Atchafalaya River as proposed, it is planned to close the present canal at its intersection with the west spoil bank of the Wax Lake outlet and reroute it from Bayou Sale Ridge to Wax Lake Pass—a wide body of water which should permit tows to traverse the outlet without danger—and from Wax Lake Pass to the lower end of Sweet Bay Lake.
The estimated cost of the treatment below Morgan City and Berwick, including the conversion to a lock of the floodgate in the lower Atcha fala ya River north of Berwick on which construction had been started prior to the war and including the necessary rerouting of the Intracoastal Canal and the provision of an alternate route for high water use landward of the east guide levee is approximately $8,000,000. It constitutes a rather major modification of the existing project which originally contemplated termination at Morgan City in the form of a ring levee. It is conceived to be within the scope of the authority over engineering aspects of the project vested in the Chief of Engineers.
In describing the state of completion of the floodway guide levees a little earlier it was mentioned that a number of gaps for roads and railroads remain. The 1936 Flood Control Act authorized the provision, at Federal expense, of three railroads and two highway crossings of the Morganza floodway and of one highway crossing, and of one railroad crossing with suitable physical connections thereto, of the west floodway.
We have built one highway and one railroad crossing over the Morganza floodway. They are United States Highway No. 190 and the N. 0. T. & M. Railway. Both run from Lottie to Krotz Springs. Some work remains to be done by way of completing the approach fill to the highway trestle and final paving may be deferred several years until rates of settlement have become small. Until that time the crossing will be usable. We have agreed on tentative locations and plans for continuing both of these crossings over the west floodway. We are having some discussion with the Louisiana Highway Department regarding the length of open trestle to be provided, and the allocation of costs for improvements over its existing facility.
By way of physical connections for the railroad crossing we are planning to raise the Krotz Springs railroad bridge about 6 feet to line it up with the two elevated crossings and make it safely usable at extreme flood stages and we are to reimburse the T. & P. R. Railroad. in a fixed sum—which offer they are still considering—for building a connecting line from Ville Platte to their tracks at Opelousas for joint use by them and the L. & A. surveys and borings for the crossings of the west floodway have been going on for some time and we hope to advertise the work in the early summer. The plans and specifications will be prepared by the owners.
The T. & P. main line crosses the Morganza floodway and McKneely to Red Cross (opposite Melville). Plans and specifications have been completed and we expect to start actual construction late next month.
At its upper end the Morganza flood way is crossed by Highway No. 30 and Port Allen branch line of the T. & P. (used as the main line of the L. & A.) We plan to use the same type railway structure as will be used between McKneely and Red Cross. The railroad and highway are to occupy the same embankment approaches but are to have sepa rate trestles. The approach fills have been constructed, but will probably require some lengthening as it now seems feasible to reduce trestle lengths. We expect to obligate $1,000,000 for the railway and $300,000 for the highway crossing this year. All of the crossings will be built under continuing contracts running about 3 years. They cost from $2,500,000 to $4,000,000 apiece.
There is only one navigation opening in the east levee; namely, the Bayou Pigeon gap discussed above, but there are several in the west levee. The uppermost is at Charenton where the war stopped construction after the concrete portions of the floodgate structure had been completed but before the gates themselves could be procured. It will be finished and placed in operation this season. The next opening is a floodgate into the Teche at Calumet on the west side of Wax Lake outlet. It is expected to advertise it for construction next month. There will also be a floodgate on the opposite side of the Wax Lake outlet or about one mile north of Patterson. There is some disagreement among local and navigation interests as to which location would be most equitable. It may finally be necessary to build two. We hope to advertise at least one of them in June.
The war also stopped construction on a floodgate at Berwick. It was about half completed and we had hoped to advertise the remainder sometime in June. A large shrimp-processing industry has developed at Patterson, however, and to avoid disruption of that traffic a lock instead of a single floodgate will be constructed at Berwick.
SOUTH BANK OF RED RIVER
In order to keep Mississippi River and Red River floodwaters from inundating the Atchafalaya Basin west of the floodways, it was necessary to build a levee along the south bank of Red River from high ground at Moncla, La., to the hills at Hot Well, La., a few miles above Alexandria. The levee leaves the Red River at Boyce, La., and runs thence to Hot Well, along the right bank of Bayou Jean de Jean.
The levee grade adopted in 1944 on the south bank of Red River was to provide a 3-foot freeboard over a flow of 215,000 cubic feet per second in Red River at Alexandria (1908 flood) meeting a 1927 flood in the Mississippi, or a 1-foot freeboard over 215,000 cubic feet per second meeting project flood in the Mississippi, whichever was highest. That grade required very material increases in actual levee height above Alexandria. Below Alexandria, the actual levee height ap. proached the new grade but was below it in many places.
Then in 1945 a flood much greater than 1908 occurred. It has an indicated average frequency of once in a hundred years. Its actual discharge at Alexandria was about 230,000 cubic feet per second and if it had been confined throughout the river above Alexandria, it would have been about 280,000 cubic feet per second. It was not confined, but on the contrary breached most of the levees above Hot Well. A survey report which is now before the Congress suggests protection against a possible flood about 20 percent greater than 1945.
If the plan of that report is adopted the south bank levee grades worked out in 1944 will not be greatly affected. The plan proposes for immediate construction a grade 1 foot above 1945 flood confined by existing and authorized levees; and an ultimate grade 3 feet above the new project flood meeting 1927 in the Mississippi or 1 foot above such flood meeting project flood with the Mississippi, whichever is higher. The levee above Alexandria, which was the stretch most in need of raising, has been in part brought to a grade 1 foot above 1945 confined and is to be practically completed to that grade next season between Alexandria and Boyce. Two or three stretches of levee already constructed to the 1944 grade may require some slight adjustment to conform with the 1945 grade and/or section.
Below Alexandria the actual freeboard in the 1945 flood was 8 or 10 feet. The levee is above the 1928 grade at most points and does not require much major raising of actual levee top even to be above a 1945 flood confined, a condition which cannot be realized for several years at least. In fiscal years 1948 and 1949, it is planned to complete the raising from Alexandria to Moncla. The levee top now is from zero to 41/2 feet below the ultimate grade with an average deficiency of perhaps 1 to 11/2 feet. A set-back may be required at Bringol, below Egg Bend, this coming season, although dike installation is planned at the locality which may obviate the need for the set-back. : From Boyce to Hot Well the levee along Bayou Jean de Jean has been temporarily topped out to a grade 3 feet above the 1945 experienced flow line. We have been asked by local and State interests to carry the line across the bayou a short distance above Boyce and tie it into the hills, providing a floodgate for the passage of the bayou flow during low stages of Red River and for the exclusion of Red River floodwaters from the lands adjacent to the bayou. This will entail impounding the bayou's flow during high Red River stages.
ow line.copped out to evee along Bavth
hills, providing Red River and to the bayouzi