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<br />Guidelines and Specifications for Flood Hazard Mapping Partners [April 2003] <br /> <br />2. Flood hazard data development, including: <br /> <br />. Generating updated flood hazard data; <br /> <br />. Redelineation of effective floodplain boundaries based on updated topographic <br />information; <br /> <br />. Creation of work maps displaying the updated / revised floodplain mapping; <br /> <br />. Creation of digital files for GIS applications; and <br /> <br />. Creation of a draft FIS report materials, including supporting flood hazard data tables <br />and Flood Profiles for flooding sources studied by detailed methods. <br /> <br />1.4.2.1 Field Survey and Topographic Data Development <br /> <br />[February 2002] <br /> <br />Accurate, up-to-date topographic data are needed when updating flood hazards with a detailed or <br />approximate engineering analysis and when redelineating floodplain boundaries using effective <br />flood elevations. Further, survey data for channel cross sections and hydraulic structures (e.g., <br />bridges, culverts, or dams) are required for detailed flood hazard analyses and may be required <br />for !';()mp. ::lpproyimMp. euginp.ering avalyse5 (if so determined dming the Project Scoping phase <br />of the Flood Map Project). <br /> <br />Significant cost savings may be realized if existing topographic and cross-section data sources <br />can be used for a Flood Map Project. Accordingly, the Mapping Partner performing the flood <br />hazard analyses shall conduct research to identify existing sources of topographic and field <br />survey data and, if such sources are found, to assess the adequacy of the data for the Project. <br />Section 1.3 of these Guidelines provides guidance on assessing the adequacy of existing <br />topographic and survey data. <br /> <br />The topographic data and the base map data used in preparing the effective FIRM must be <br />compatible; that is, like features in both data sources must align. If the Mapping Partner <br />performing the flood hazard analyses determines that no data exist or that existing data are <br />inadequate or need to be supplemented, then that Mapping Partner shall develop the necessary <br />data following the guidance in Appendix A of these Guidelines. <br /> <br />Bench Marks <br /> <br />Vertical control monuments (also referred to as bench marks) must be shown on the FIRM to <br />assist map users in establishing vertical control for flood elevation determinations. Bench marks <br />shown on the FIRM must meet a minimum qualifying standard; they must be First or Second <br />Order Vertical and have a stability classification ranking of A, B, or C as defined by the National <br />Geodetic Survey (NGS). All qualifying bench marks within a given jurisdiction that are <br />cataloged by the NGS and entered in the National Spatial Reference System (NSRS) with the <br />aforementioned qualifications shall be shown on the FIRM and identified by their NSRS <br />Permanent Identifier (PID). <br /> <br />1-58 <br /> <br />Section 1.4 <br />