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Show watts will be located largely in the Southeastern and Southwestern States. On the other hand, no projects which include hydroelectric power, either constructed, under construction, or author- ized, are shown for New England. In this con- nection it may be noted that there are 13 addi- tional projects at which some 700,000 kilowatts of hydroelectric capacity may ultimately be in- stalled, but which are presently authorized for flood control only. Old and New Projects The existing flood control program is a com- bination of a variety of methods of providing pro- tection. It includes channel clearance and im- provement, construction of levees and other local protection works, construction of dams designed merely to hold the floods long enough to release the waters without overflowing the banks of the stream below, and true conservation storage reser- voirs designed to regulate the flow of the stream for all beneficial purposes, including the genera- tion of hydroelectric power either at the project or at other projects lower down on the stream. A decision to continue the progress toward flood control programs designed to utilize flood- waters rather than merely to restrain their vio- lence, may involve a change in design of the dam to provide additional reservoir capacity for con- servation storage. It may involve the construc- tion of power facilities for present or future utili- zation of the stored floodwaters to generate elec- trical energy. But it may involve much more in terms of design of the entire basin program and the interrelation of projects. Specifically, it may require the relocation of proposed flood control reservoirs so as to permit the greatest possible utilization of falling waters. As far as economically possible, the entire fall from the headwaters to the sea, should be utilized to produce hydroelectric power. This means flood storage reservoirs on the tributaries of larger streams. Insofar as this point of view governs the plan- ning of flood control, the possibilities of flood management begin to expand. It becomes pos- sible to get greater uses out of reservoirs as a group than out of the sum of their uses operated sepa- rately. Headwater reservoirs, tributary reser- voirs, and main stem developments play their respective parts in an integrated hydraulic and power operation. In certain regions the estab- lished seasonal characteristics of floods can be taken into consideration, providing more storage space in the reservoir for flood waters in the season of largest volume floods and correspondingly more storage for power generation in periods of peak demand for electricity. Investigations along these lines reveal that the more flood control projects are designed for con- servation storage and hydroelectric power, the more flood protection becomes economically jus- tifiable. To accomplish these purposes fully, however, will require a shift of public viewpoint in certain areas. To a very large extent the coun- try's great hydroelectric potentialities are merely the potentialities of controlled floodwaters. Flood Plain Zoning As the entire manner of handling floods is re- viewed, it will be possible to determine basin by basin how much of the excess of floodwaters, re- sulting from melting snows and heavy rains, over and above those which it is found feasible to store in surface and underground conservation reser- voirs, would be passed down the main stem be- tween its system of levees to the sea. These floodwaters contain silt loads of organic matter and sediment derived from erosion of stream banks of cultivated slopes. This sediment burden of flood or storm waters is generally rich in fertility elements which are lost when carried out to sea. These fertile sediments in past floods that spread out over the flood plain were mostly de- posited, raising the flood plain and adding to its fertility each time. For this reason, flood man- agement should in general recover as much as is feasible of the sediment that is carried along in a flood current. This may be accomplished by admitting floodwaters to floodways back of levees. It would broaden our present provisions for deal- ing with floods to include the values obtained by 144 |
