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- PREFACE - It should be noted that the terms "Intermediate Regional Flood", "lOO-Year Flood", and "one percent flood" can be used interchangeably as they are all defined by the same type of flood event. Authorization This report was authorized by the Urban Drainage & Flood Control District in joint sponsorship with the Colorado Water Conservation Board. The District has the power to enact District-wide flood plain regulations. At present, the District makes flood plain information and mapping available for local agencies to adopt and administer their own flood plain regulations with the assistance of the District. Purpose and Scope This report was prepared for the guidance of local officials in planning the use and regulation of the flood plain. The report includes information on past floods and the nature and extent of probable future floods which can b~reasonably expected on the respective study reaches. The 100-year flood should be given appropriate consideration before planning for development in the flood plain. The Colorado Water Conservation Board has the power and duty "...to designate and approve stGrm or floodway run- off channels or basins, and to make such designations available to legislative bodies of cities and incorporated towns 1 to county planning commissionsl and to boards of adjustment of citiesl incorporated townsl and counties of this state..." as stated in Section 37-60-106 (1) (c) of the Colorado Revised Statutes 1973. The cities, incorporated towns and counties within the study area may provide zoning regulations... "...to establish, regulate, restrict, and limit such uses on or along any storm or floodwater runoff channel or basin, as such storm or floodwater runoff or basin has been designated and approved by the Colorado Water Conserva- tion Board, in order to lessen or avoid the hazards to persons and damage to property resulting from the accumu- lation of storm or floodwaters..." The 100-year flood plain is shown on the Flood Hazard Area Delineation Maps which delineate the areas that would be inundated by such an event. Flood profiles show the water depths relative to the stream bed. Elevation reference data is given that can be applied across the full width of the stream valley. Valley cross sections are presented to indicate ground level across the valley at specified locations and the overlying flood depths. The flood profiles and flooded area data presented are based on future, developed con- ditions in the basin as determined from current master planning maps. possible future improvements to control floods are not a consideration of this report. as stated in Section 30-28-111 for the county governments and Section 31-23-201 for municipal governments of the Colorado Revised Statutes 1973. The information in this report does not imply any State action to zone or regulate use of flood plains. The District has the authority to regulate flood plains, but to date has chosen to leave flood plain regulation responsibility with local governments. The report provides a suitable basis for the adoption of land use controls to guide flood plain management, with consideration for environmental attributes, and thereby prevent intensification of flood losses. Upon acceptance of this report by the Urban Drainage & Flood Control District and the designation and approval of this report by the Colorado Water Conservation Board, the areas described as being inundated by the 100-year flood (Intermediate Regional Flood) can be designated as flood hazard areas and their use regulated accordingly. Flood water surface elevations and flood plain boundaries are often revised by road and bridge construction, flood plain developmentr