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<br />. <br /> <br />OBJECTIVES <br /> <br />The primary objective of this study is to provide large scale <br />mapping with flood hazard and mudflow information. The information is <br />needed by Chaffee County for flood plain zoning ordinances and other <br />land use controls to reduce potential damages from floods and mudflows <br />in the hazardous areas. The engineering and hydrologic information to <br />De developed during the study will De of use in developing a master <br />drainage plan, in road and bridge planning and design, and in the <br />planning of flood control structures, if needed. <br /> <br />INTENSITY OF tNVESTIGATIONS <br /> <br />Studies will be undertaken to develop flood hazard information <br />for the 10-, 50-, 100-, and 500-year frequency floods under existing <br />channel and flood plain conditions, Photogrammetric maps with topog- <br />raphy, planimetry, and flood plain information for the 100- and 500-year <br />frequency floods will be prepared on a scale of 1" = 400', The contour <br />interval will be two feet in the flatter flood plain areas and an <br />appropriate contour interval will be used in the steeper areas compat- <br />ible to the scale of mapping. <br /> <br />. <br /> <br />Data such as flood history, photos, present and projected use, and <br />other pertinent information will be collected for use in the study. <br /> <br />Engineering field surveys will be conducted to establish vertical <br />and horizontal ground control and to obtain dimensions of bridges and <br />culverts. About 170 flood plain cross-sections will be needed to ade- <br />quately define the hydraulic relationships, ,Cross-section data will be <br />obtained photogrammetrically where feasible. <br /> <br />The magnitude, elevation, and location of flooding for the designated <br />frequency floods will be developed from hydrologic and hydraulic analyses <br />using standard Soil Conservation Service techniques and procedures. <br /> <br />The study area includes a mudflow which has caused problems in <br />the past. The state and local units of government are interested in <br />identifying areas of natural hazards including mudflows, The intensity <br />of investigations for this study will be confined to providing historical <br />mudflow information and identifying the problem locations on the study <br />area maps. <br /> <br />. <br /> <br />2 <br />