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<br />. <br /> <br /> <br />. <br /> <br />CHAPTER 4 <br />FLOODPLAIN <br />ADMINISTRATION <br />AND <br />DELINEATION <br />.ECTION 1.0 <br />LOODPLAIN <br />MANAGEMENT <br /> <br />COLORADO STATEWIDE <br />DRAINAGE AND FLOODPLAIN MANAGEMENT CRITERIA MANUAL <br /> <br />1.14 FLOODPLAIN MODIFICATION STUDY <br /> <br />A Floodplain Modification study is required when there is a <br />proposed modification to a 100-yearfloodplain orfloodway. <br />All non-exempt floodplain developments shall prepare and <br />submit a Floodplain Modification Study for review and <br />approval by the local govemment agencies and the <br />Colorado Water Conservation Board. The general outlines <br />for a Floodplain Modification Study are provided in Section <br />1.14.2. For modification of a FEMA floodplain, a LOMR <br />request report may be submitted in place of a Floodplain <br />Modification Study. <br /> <br />A Floodplain Modification Study or a LOMR request report <br />shall demonstrate that the proposed project meets the <br />floodplain development guidelines and that the upstream, <br />adjacent, and downstream properties are not being <br />adversely impacted. The study shall be professionally <br />prepared, legible and reproducible. <br /> <br />All non-exempt <br />floodplain <br />developments <br />shall prepare <br />and submit a <br />Floodplain <br />Modification <br />Study for review <br />and approval by <br />the local <br />government <br />agencies and the <br />Colorado Water <br />Conservation <br />Board. <br /> <br />1.14.1 FLOODPLAIN MODIFICATION STUDY REQUIREMENTS <br /> <br />A Floodplain Modification Study shall be submitted for the following activities: <br /> <br />1. As an initial feasibility study to determine the potential utilization of a <br />site with floodplain impacts. <br /> <br />2. Attempting to develop in the 100-year floodplain designated by FEMA <br />and/or the community. <br /> <br />3. Restudy and revision of a previously delineated floodplain. <br /> <br />4. Public works improvements effecting the designated 100-year <br />floodplain <br /> <br />The effort necessary for a Floodplain Modification Study is dependent <br />upon the amount of information previously generated, the potential for <br />impact on adjacent properties, the magnitude of flow in the channel, the <br />size of the area affected, the need for channel stabilization, and the <br />sediment transport and fluvial morphological aspects of the stream. If <br />there is no existing floodplain delineation for the drainageway in question, <br />the applicant will be required to produce one (refer to Section 2, Chapter <br />4). The applicant is not required to submit a separate FlOodplain <br />Delineation Study report (Section 2.11, Chapter 4) if the new floodplain <br />delineation information is included in the Floodplain Modification Study. <br />A Floodplain Modification Study must be certified by a registered Civil <br />Engineer licensed to practice in the State of Colorado. The following is a <br />list of general requirements for the Floodplain Modification Study: <br /> <br />1. <br /> <br />Hydrologic analyses should be performed to determine the <br />existing and proposed conditions flow rates at selected <br />concentration points and to determine the potential impacts <br />cause by the proposed project. Please refer to Chapter 5 for <br /> <br />FLOODPLAIN CH4-111 <br />MANAGEMENT <br /> <br />AUGUST 2002 <br />