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<br />. <br /> <br /> <br />. <br /> <br />CHAPTER 4 <br />FLOODPLAIN <br />ADMINISTRATION <br />AND <br />.ELlNEATION <br />SECTION 2.0 <br />FLOODPLAIN <br />DELINEATION <br /> <br />COLORADO STATEWIDE <br />DRAINAGE AND FLOODPLAIN MANAGEMENT CRITERIA MANUAL <br /> <br />CHAPTER 4 <br />FLOODPLAIN ADMINISTRATION AND DELINEATION <br /> <br />SECTION 2.0 <br />FLOODPLAIN DELINEATION <br /> <br />2.1 INTRODUCTION <br /> <br />In order to regulate existing and new floodplain improvements and to reduce the <br />amount of future losses due to flooding, flood hazard areas should be clearly' <br />identified, studied, and delineated. <br /> <br />Many drainage-ways have been analyzed by various local, state, and federal <br />agencies, and their floodplain delineations can be found on either the Flood <br />Insurance Rate Maps (FIRMs) published by the Federal Emergency Management <br />Agency (FEMA) or the community's floodplain maps. However, throughout the State, <br />numerous floodplain areas that are subject to severe flooding have not yet been <br />studied and delineated. As new developments occur in these undetermined flood <br />hazard areas, local agencies and developers face the challenge of developing the <br />flood hazard area information. <br /> <br />This section is intended to provide practical guidelines for delineation of flood hazard <br />areas within the State of Colorado. Readers of this manual are encouraged to review <br />the following publication for more detailed discussions on this subject: <br /> <br />. Federal Emergency Management Agency, NFIP Regulations, Title 44, <br />Chapter 1, Part 65, Identification and Mappina of Special Hazard Areas, <br />revised October 1999. <br />. Federal Emergency Management Agency, Flood Insurance Stuctv Guidelines <br />and Specifications for Studv Contractors, March 1993. <br /> <br />2.2 LEVEL OF STUDY <br /> <br />Flood hazard areas can be delineated based on two <br />different analysis approaches: detailed and limited <br />methods. The detailed study approach should be used <br />when accurate floodplain information including floodplain <br />limits, water surface elevations and profiles, flood depths <br />and velocities and, f100dway limits, are needed for the <br />drainage-way being studied. The limited study method may <br />be used when detailed floodplain information is not <br />necessary. The limited study usually results in the <br />delineation of approximate flood hazard areas without base <br />flood elevations. <br /> <br />Flood hazard <br />areas can be <br />delineated based <br />on two different <br />analysis <br />approaches: <br />detailed and <br />limited methods. <br /> <br />The following factors should be considered when deciding which study approach to <br />use for a drainageway being studied: <br /> <br />. Size of the contributing watershed <br />. Size and stability of the drainageway <br /> <br />AUGUST 2002 <br /> <br />FLOODPLAIN DELINEATION <br /> <br />CH4-203 <br />