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<br />. <br /> <br />. <br /> <br />. <br /> <br />digital technique. Floodplain delineations for the SOD-year flood are encouraged, but not <br />required, by the CWCB. The CWCB shall only designate and approve 100-year <br />floodplain information. <br /> <br />C. Base Mapping. Base mapping for floodplain studies shall meet the minimum standards as set <br />forth in Appendix A and any other method approved by the Board. <br /> <br />D. Topography and Surveys. Topographic and field survey information for floodplain studies <br />shall meet the minimum standards as set forth in Appendix A. <br /> <br />E. Vertical Datum and Horizontal Control. <br />a. New topographic information obtained for floodplain studies in Colorado shall be <br />produced using a vertical datum standard based on NA VD 1988, Existing flood profiles <br />and Base Flood Elevations based on NGVD 1929 Datum shall be converted to NA VD <br />1988 for the purposes of new and revised floodplain mapping studies. New stndies, <br />utilizing previous topographic information that was originally developed using NGVD <br />1929 vertical datum, shall be produced on NA VD 1988 datum by appropriately <br />converting the vertical information to the new datum for modeling and mapping <br />purposes. <br />b. The accepted Horizontal Projection standards are UTM (Zone 12 or 13 depending on <br />Geographic location within the state) and State Plane coordinates. <br />c. Additional requirements are set forth in Appendix A. <br /> <br />F. Geographic Information Systems (GIS). GIS information for floodplain studies in Colorado <br />shall meet the minimum standards as set forth in Appendix A, New floodplain studies <br />submitted for CWCB designation and approval shall be in conformance with CWCB approved <br />GIS standards for digital floodplain information. <br /> <br />11 <br /> <br />DRAFT <br />