TABLE 22.-Comparative annual rates of sediment contributed to streams from treated and untreated uplands These estimated reductions in the rate of sediment contribution to flood plains will prevent sediment damages in the amount of about $700,000 annually after the program has been in for 20 years. This benefit will increase to approximately $1,750,000 in the eightieth year after installation. An even greater benefit, however, will be realized through the alleviation of past sediment damages although its rate of accrual is slower. As sedimentation falls below the critical rate, the increased transporting power of stream discharge will enable it to pick up sediment in the channels and flush it out of the drainage systems. This process will result in less overbank flooding as stream channels become enlarged; in the somewhat distant future, it will permit some beneficial siltation when floods that do go overbank transport and deposit fertile soil rather than coarse sand. The anticipated alleviation of past sediment damage is valued at only $144,000 in the twentieth year after the program is installed but this type of benefit will increase in the eightieth year to more than $2,300,000. As the quantity of flood-borne sediment is increasing at an alarming rate, this represents a potential hazard to the operation of floodcontrol reservoirs in this watershed. The United States Engineer Department 27 estimates that some structural alterations will be needed on the Enid Dam when the reservoir has lost about 12% percent of its flood-storage capacity. Sediment source studies indicate that this condition will occur in some 100 years if sedimentation is uncontrolled. In the Arkabutla and New Grenada Reservoirs, the permissible storage loss will be about 17%1⁄2 percent of total capacity and must be rectified in about 90 years. When the recommended program is carried out, sediment rates will be so reduced that indicated improvements should be unnecessary for over 300 years on the Arkabutla Reservoir, 500 years on the New Grenada Reservoir, and 600 years on the Enid Reservoir. For all practical purposes the program may be assumed to eliminate this sedimentation damage to reservoirs. The annual benefit of eliminating this damage is $12,376, if the cost of improvements made necessary due to sedimentation is assumed to be $9,000,000. 27 Estimates obtained in conferences and correspondence with U. S. Engineer Department, Vicksburg, Miss. Indirect benefits. The effect of floods on transportation facilities, the interruption of regular or planned business, the reduction in farmer purchasing power, and many other indirect damages are suffered as the result of floods and damaging sediment. Indirect damages are considered to amount to at least one-fourth as much as all direct flood damages. Likewise, indirect flood-control benefits are assumed to accrue at the same ratio to direct flood-control benefits, although studies indicate a higher ratio could be adopted. They will amount to approximately $335,000 annually. ON-SITE CONSERVATION BENEFITS On-site benefits, as the name applies, accrue on the land to which remedial measures are applied. They consist chiefly of increased yields of crops, livestock, and timber or they may take the form of reduced maintenance expenses as in the case of controlling erosion on public roads. In general, most on-site benefits accrue to private individuals, although the public will be the recipient of benefits accruing on public lands, such as increased revenue from the sale of timber stumpage, the rental of certain lands for agricultural and grazing use, and the savings in maintenance costs from controlling highway erosion. The on-site benefits are of considerable practical importance from the standpoint of program accomplishment. They provide the main incentive for individual participation in establishing remedial measures. Practices that will demonstrably increase farm incomes by improving crop yields, doubling the carrying capacity of pastures, and multiplying by many times the present forest income, will appeal to landowners and will enlist a type of cooperation that would be largely lacking if justification for this work depended solely on potential flood-control benefits accruing to the special advantage of other lands. TABLE 23.-Annual on-site benefits after recommended program reaches full effectiveness 1 [Benefits shown have not been reduced to present values] Watershed. $1, 542, 507 $33, 448 $640, 144 $127, 796 $33, 590 $2, 182, 651 $194,834 $2,377, 485 308,020 1,625, 076 591, 212 3, 586, 999 233, 584 2,380, 832 927,852 4,598, 848 6, 620, 183 285, 226 5, 693, 545 1, 757, 366 212, 910 12, 313, 728 2, 255, 502 14, 569, 230 1 Full effectiveness reached on open land 25 years after full installation of the program, on forest land in 58 years, and on road banks within a year after treatment. Rental of public land suitable for cultivation or pasture. Represents stumpage value only. Reduced maintenance costs. The on-site benefits will total almost 15 million dollars annually after the program is fully effective and more than half of this annual amount will accrue the tenth year after the program is installed. When the program is fully effective, this increased income will be equivalent to an average return of $478 annually for every rural family in the watershed plus an additional public income of over $2,250,000 (table 23). General economic benefits. The prospective benefits are of such magnitude that either the public flood-control benefits or the private conservation benefits will amply justify the entire program. Many other benefits will result from accomplishment of the proposed program and will affect favorably the economy of the entire basin. Some of these are: Increased opportunities for employment; stabilization of agriculture and industry; more adequate recreational facilities; the alleviation of problems of indebtedness, tenancy, taxation, and public health. These benefits will have regional implications of considerable magnitude as well. Installation of the program will require approximately 886 additional man-years of labor annually over the 20-year period. After the program has reached full effectiveness, the annual labor increase, including that required to harvest the added production of crops and timber, will amount to about 3,400 man-years.28 Much additional labor will be required in the primary and secondary manufacture of products. The additional production from improved forests, for instance, will require about 6,700 man-years to operate local sawmills and several times this amount will be utilized in secondary processing enterprises. These increased outlets for labor will develop progressively after installation of the program but will not provide sufficient immediate employment to alleviate materially the problem of relocating families now occupying submarginal lands unsuitable for private ownership. Increases in incomes and resultant higher standards of living will help meet the problems of indebtedness, taxation, tenancy, and related problems confronting the area. The proposed program will not directly solve these problems but will aid in their ultimate solution. Incident to a public-purchase program will be the development of roads and recreational facilities to serve the area. Some few improvements of this nature have already been installed by public agencies now operating in the area, and an expanded public program will give impetus to fulfillment of these needs. SUMMARY OF BENEFITS When all measures have become fully effective, the monetary benefits from the recommended program will total almost $21,000,000 annually (table 24). More than $6,000,000 of these benefits is a direct result of reducing flood and sediment damage on valley lands and the remainder represents the on-site benefits accruing on treated lands. In addition, many intangible benefits will contribute materially toward the stabilization of agriculture and a higher standard of living. These labor increases are net changes and include a deduction for losses in farm labor as a result of the public-purchase program. TABLE 24.-Annual monetary benefits when the recommended program approaches maximum effectiveness [Benefits shown have not been reduced to present values] 1 Brought about through run-off reductions. Maximum effectiveness reached about 25 years after the program is installed. 2 Includes prevention and alleviation of all forms of sedimentation damage including that causing increased flooding. Benefits shown are those that will accrue in 80 years after installation of the program. These benefits will increase indefinitely, since alleviation processes are gradual. They will level off to some extent after about 200 years. These are benefits on open and forested land in public and private ownership. The benefits on open land will reach maximum effectiveness 25 years after installation of the program. Benefits on forested land will reach maximum effectiveness in about 60 years. Benefits, or reduced maintenance costs, on treated roadbanks will accrue immediately following treatment and amount to about 10 percent of all publie on-site benefits. Will accrue in full 80 years after installation of program and will continue to increase slightly thereafter. When all future benefits, some of which may be realized at an early date and others many years later, are converted to an average basis they amount to the following: Flood and sediment reduction_. Conservation or on-site--- Total.. CHAPTER V. EVALUATION OF THE PROGRAM annual $1,675, 618 6, 455, 851 8, 131, 469 Costs and benefits of the recommended flood-control program do not accrue at regular rates or in proportional amounts. Some measures entail high initial costs and yield deferred benefits while others are relatively inexpensive and confer substantial benefits almost immediately. Heretofore, costs and benefits have been discussed in terms of actual values as these will be incurred or realized at specific times in the future. In order to compare costs and benefits, it is necessary to eliminate the element of time by converting all such values to present worth and reducing the latter to average annual amounts.29 29 This program is evaluated using an interest rate of 32 percent. Future costs and benfits are discounted to present-worth values by applying appropriate discount factors to each value each year until it levels că The annual amount at the leveling-off point is capitalized and likewise reduced to present worth by the proper discount factor. 32 percent of the sum of present-worth values represents an average annual value. COSTS OF THE PROGRAM The average annual cost of the recommended program will amount to $3,565,388 or slightly more than $1.50 per treated acre (table 25). Of this total cost, approximately 69 percent is private, 30 percent Federal, and about 1 percent State and local government. Costs per acre treated in the various drainage units are nearly uniform, amounting to $1.47 in the Coldwater, $1.34 in the North Bluff, $1.51 in the Yalobusha, $1.59 in the Yocona, and $1.63 in the South Bluff. TABLE 25.- Average annual cost of the flood-control remedial program Average annual benefits will amount to $8,131,469, of which 21 percent is flood-control or off-site benefits and 79 percent is the conservation benefits. Approximately one-third of all benefits are public and the remaining two-thirds will accrue to private interests (table 26). As with costs, the benefits per acre of land treated vary little between drainage units, being $3.30 in the Yalobusha, $3.12 in the Yocona, $3.70 in the Coldwater, $3.64 in the North Bluff, and $3.44 in the South Bluff. COMPARISON OF COSTS AND BENEFITS For each dollar of annual cost of the proposed program, $2.28 will be returned as benefits. Benefits per dollar of cost range from $1.96 in the Yocona to $2.72 in the North Bluff (table 27). Federal participation in the recommended program is clearly justified, as the flood-reduction benefits alone have an appraised value approximately one and three-fifths times that of all Federal costs. State and local governments will receive proportionately larger benefits having an aggregate value approximately four times that of contributed costs. Private interests are the major beneficiary. They will receive about $2.25 of on-site benefits per dollar of cost and in addition will share in the greater part of the flood-reduction benefits. On the basis of the foregoing, it is evident that a corrective floodcontrol program is fully justified in all portions of the watershed. |