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. . OBJECTIVES The primary objective of this study is to prepare flood plain maps for flood plain zoning ordinances and other land use controls, as needed, to reduce potential flood damages and unwise development in the flood plain. The engi- neering and hydrologic information to be developed during the study will be of use in developing a master drainage plan, in road and bridge planning and design, and in the planning of flood control structures, if needed. INTENSITY OF INVESTIGATIONS Studies will be undertaken to develop flood hazard information for the 10-, 50-, 100-, and SOD-year frequency floods under existing channel and flood plain conditions. Photogrammetric maps with topography, planimetry, and flood plain information for the 100- and SOD-year frequency floods will be prepared on a scale of 1" = 400'. The contour interval will be two feet in the flatter flood plain areas and an appropriate contour interval will be used in the steeper areas compatible to the scale of mapping. Available basic data such as flooding history, photos, land use, and existing survey data will be collected. Pertinent data from this information will be used in the study. Engineering field surveys wil1 be conducted to establ ish vertical and horizontal ground control and to obtain dimensions of bridges and culverts. About 170 flood plain cross-sections will be needed to adequately define the hydraul ic relationships. Cross-section data will be obtained photogramme- trically where feasible. The magnitude, elevation, and location of flooding for the designated frequency floods will be developed from hydrologic and hydraulic analyses using standard Soil Conservation Service techniques and procedures. - 2 - The Water Resources Council tentative guidel ines for flood hazard evalua- tions will be used for recommendations on flood plain land use and management regulations. INTERAGENCY COORDINATION Close coordination will be maintained through the representatives of the Colorado Water Conservation Board, the San Juan Soil Conservation District, the Upper San Juan Region 'Planning Commission, Archuleta County, the Town of Pagosa Springs, and the Soil Conservation Service to assure the completion of the study in a timely manner. Coordination with the Corps of Engineers and other concerned federal agencies will be maintained throughout the study by the Colorado Water Conservation Board.