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Halligan Reservoir, built on the North Fork Cache la Poudre River, has attenuation effects downstream. Although the reservoir does not have specific flood control storage, floodflows are delayed by their passage through the reservoir spillway and are, thus, reduced. . On the plains, the cumulative incidental flood control effects of reservoirs can be significant as Water is diverted from streams to fill storage in the reservoirs. Peak discharges on the Cache la Poudre River are attenuated considerably by these diversiuns. Peak discharges are also attenuated by valley storage. Discharges are reduced as floods spread out tD fill the broad Cache la Poudre River Valley. On the smaller tributaries, diversion dams or canals may absDrb normal high flows and result in complacency about flooding. Und~r the provisions of the Watershed Protection and Flood Preven- tion Act, Public Law 566, a Soil Conservation Service watershed project for Boxelder Creek is under construction. The project includes land treatment measures together with ~onstruction of five single-purpose floodwater-retarding structures and one grade-stabilization structure, The Soil ConservatiDn Service estimates that the project may reduce floodwater damages in the watershed by $171,310 annually, REGULATION Flood plain land use within the city limits of Greeley and Fort CDllins is regulated by the respective city. All other flood plain land use is regulated by Larimer Dr Weld County, The city of Greeley adopted a zoning ordinance in July 1976 which requires construction of detention ponds in new subdivisions designed to assure that development of the subdivision will not increase runoff. The city, however, has not enacted flood plain ordinances sufficient to be included in the National FloDd Insurance Program as of this report. 12 .