525. It will be noted that there is an existing flood-control project for the Tulsa and West Tulsa levees, Oklahoma, and that the project included in table No. 95 provides only for the alteration of the St. Louis-San Francisco Railway bridge. The existing project, as authorized, did not provide for raising the bridge, either by the Federal Government or the local interests. Owing to an increase in the design flood subsequent to authorization of the project, it is necessary to raise the bridge 6 feet in order to safeguard the flood-control structures at the locality which are now under construction. Assurances of local cooperation given by the local interests have already been approved by the Secretary of War. These assurances do not include raising the bridge. For these reasons, it is proposed that the entire cost of the bridge alteration, including alterations to the bridge approaches, be borne by the Federal Government. Ove to loc the ble ther 526. Studies of the waterway openings for various bridges below any adve er and s 527. The estimated costs of raising the Missouri Pacific Railroad quen tertain tributary streams would be diverted. It is proposed that the local ther interests stand the cost of these county bridges. flood-c pro ides 528. All projects included in the plan of improvement are cons he pro beer bout fe on 30. T dificat of is, is gr Litt on hold and save the United States free from damages due to the construction works; and maintain and operate all the works after completion in accordance with regulations prescribed by the Secretary of War. The extent of local cooperation proposed for bridge alterations has been discussed previously. The estimated first cost of the projects included in the plan of improvement is $13,276,000, of which $12,127,000 is the Federal cost. The projects would provide flood protection for 134,130 acres of land. Important urban properties at certain cities and towns along the Arkansas River are included in this area. 529. Other projects considered, but not included in the plan of improvement, were eliminated owing to lack of economic justification or to local opposition to the projects. In determining grades for the levee projects included in the plan of improvement, these projects have not been considered; therefore, none of them should be authorized without first giving consideration to the adverse effect they might have on other projects. 530. The projects included in the plan of improvement involve modification of seven authorized flood-control projects. This modification of authorized projects, caused mainly by the higher levee grades, is deemed essential in view of the experience gained from the recent great flood (May 1943). The west end portion of the authorized Little Rock levees, included under "Other projects considered" in table No. 95, is too low in economic justification to be undertaken. It is therefore considered that the west end portion of the authorized Little Rock levees should be abandoned. 531. The improvements proposed in this report would not adversely affect any authorized flood-control or navigation project, nor would they adversely affect any existing flood-control works or the regimen of the Arkansas River. Consideration is now being given to other stream-improvement projects along the main stem of the Arkansas River and on certain tributary streams, which will be covered by a subsequent report. The conclusions reached in this latter report may render it advisable to modify to some extent the local flood-control projects included under the plan of improvement. Therefore, it is believed that if the general plan for local flood protection proposed in this report should be authorized for construction, the authorization should be subject to such modification as in the discretion of the Secretary of War and the Chief of Engineers may be advisable. GENERAL CONCLUSIONS 532. A study of the flood problem along the Arkansas River indicates that the most feasible plan for providing local flood protection involves the use of levees and flood walls at separated localities along the river, supplemented by tributary stream channel diversions at certain localities. Therefore, a number of levee and flood-wall projects between Tulsa, Okla., and Pine Bluff, Ark., are proposed for construction and have been included in the plan of improvement. Six of these proposed projects contemplate a modification of authorized flood-control projects to provide for higher levee grades. One of the proposed projects, viz, Tulsa and West Tulsa Levees, Okla., provides for a modification of the authorized flood-control project to include the raising of the St. Louis-San Francisco Railway bridge at Federal expense. 533. Each of the projects included in the plan of improvement is considered to be economically justified and is desired by the local interests. These projects would provide protection for 134,130 acres of land, including important urban properties. The estimated first cost of the projects included in the plan of improvement is $13,276,000, of which $12,127,000 is the Federal cost and $1,149,000 is the cost to local interests. 534. Owing to the very low cost to benefit ratio for the West End portion of the authorized Little Rock levees, it is believed that this portion of the authorized flood-control project should be abandoned. RECOMMENDATIONS 535. It is recommended that the projects included in the plan of improvement as set forth in this report, including the necessary modification of authorized flood-control projects, be constructed at an estimated cost to the United States of $12,127,000, with such modifications thereof as in the discretion of the Secretary of War and the Chief of Engineers may be advisable, provided the local interests assume the obligations of local cooperation as set forth herein for each project. It is further recommended that the West End portion of the authorized levee project at Little Rock, Ark., be abondoned. A. M. NEILSON, [First Endorsement] OFFICE, DIVISION ENGINEER, To: The Chief of Engineers, United States Army. 1. The district engineer has investigated the feasibility of affording protection from floods to as many affected cities, communities, and agricultural areas as was possible in the reach of the main stem of the Arkansas River from Great Bend, Kans., to Pine Bluff, Ark. Such investigations included not only those localities that are now partially protected, but also included many others that are at present unprotected. Detailed studies were made of the direct and indirect damages that would be prevented by the desired improvements, and also of all other benefits that could reasonably be expected to accrue from construction of those improvements. Some of those latter benefits, although of an intangible nature, are nonetheless real, and in many instances are of sufficiently far-reaching importance as to warrant making a favorable recommendation for the project, despite an appar ently unfavorable ratio of economic justification on the basis of those benefits that could be evaluated in purely monetary terms. 2. The plan of improvement, as formulated by the district engineer, provides for a coordinated system of earth levees, and concrete floodwalls, where necessary in congested or highly industrialized urban project One o the effec mmend Distri areas, supplemented by diversion of tributary streams at a few localities. The levees in the system would protect against a recurrence of all experienced floods of record, after taking into account the regulating effect on flood flows which would result from the operation of reservoirs which have been completed, and including the additional effect of Fort Gibson Reservoir on Grand (Neosho) Řiver, Okla., the construction of which for flood control and power development was initiated but later suspended for the duration of the war emergency. The levee grade profile was calculated to provide a freeboard of 1% feet and 3 feet for agricultural and the larger urban areas, respectively, above the flow line of the confined design flood. 3. After making a reconnaissance of the valley, 46 areas appeared most likely to be worthy of flood protection, and of that number 20 were finally included in the recommended plan of improvement, after giving due weight to all pertinent engineering and economic factors. Some were rejected because local interests either did not desire construction of the works proposed, or were unwilling to meet the prescribed requirements of local cooperation; still others were rejected because of the relatively high cost of construction as compared with the value of the lands and properties protected, or with the benefits to be anticipated to accrue from adequate protection. 4. In this connection, it is desired to emphasize certain particularly important aspects of this coordinated plan for local flood protection along the Arkansas River. Between Tulsa, Okla., and the vicinity of Pine Bluff, Ark., upstream from the head of backwater from the Mississippi River, there are about 750,000 acres of valley lands that are subject to overflow. Of that amount the recommended plan contemplates providing protection to about 134.000 acres, with consequent loss in valley storage. Furthermore, the flow line of the design flood discharge is based on the confinement that will be effected by construction of the recommended levees, as well as by those existing levees previously authorized by Congress and constructed by the Engineer Department in recent years, and for which no project modification is proposed herein. Therefore, if any additional projects are authorized for construction which are not now included in the plan outlined, such additions will adversely affect the grades of adjacent recommended levee projects because of the increased confinement of flows. As a further result construction costs will obviously be increased, possibly even to the extent that the economic justification for construction of the projects involved may become unfavorable. 5. One other problem warrants special emphasis, and that relates to the effect that construction of certain of the levee projects in the recommended plan of improvement will have upon nearby bridges. The District Engineer has pointed out in his report that it will be necessary to raise four bridges over the main stem of the Arkansas River, namely: St. Louis-San Francisco Railway bridge at Tulsa, Okla.; Missouri Pacific Railway bridge at Fort Smith, Ark.; United States Highway No. 64 bridge at Van Buren, Ark.; and Arkansas State Highway bridge at Morrilton, Ark.; because the low steel of those structures is lower than the computed elevation of the confined design flood. With respect to the bridges at Fort Smith, Van Buren, and Morrilton, Ark., the district engineer has recommended that the Federal Government bear the cost of raising the structures themselves and that local interests bear the cost of altering the approaches, as part of the requirements of local cooperation. As regards the railroad bridge at Tulsa, Okla., however, the district engineer has recommended that the Federal Government bear the entire cost of raising both the bridge and its approaches. With this latter recommendation I do not concur, since it is my opinion that alterations to all the bridge approaches are a proper charge to local interests. 6. On the basis of the comments in the preceding paragraph, and allocating the cost of bridge alterations to the various levee projects which would, by confining the flow, contribute to the necessity for raising the structures, the following apportionment of Federal to nonFederal costs is determined upon: Distribution of costs by proposed projects From examination of the above table it seems evident that authorization for all projects affecting any one bridge should be made as a group, and similarly that construction of the projects in that group should be undertaken concurrently in order that sufficient funds would be available for each bridge alteration, when once such construction is started. 7. Subject to the foregoing comments, I concur in general in the conclusions of the district engineer, and in recommending that the United States construct local flood protective works along the main stem of the Arkansas River, substantially in accordance with the plans of improvement outlined in the report of the district engineer, but with such modifications as, in the discretion of the Secretary of War and of the Chief of Engineers, may be found advisable, at a total estimated cost to the Federal Government of $12,060,000, including $1,012,000 estimated as the cost of making certain necessary alterations to two railroad and two highway bridges located at Tulsa, Okla., Fort Smith, Van Buren, and Morrilton, Ark., respectively; provided follow Jenks, Dirty C Tucker Braden Moffett Conwa Roland That auth tural Hutchin |