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<br />,~- - .~ <br /> <br />Comparison of 1975 Model Floodplain Regulations with <br />Revised Model Floodplain Regulatlons <br /> <br />The following are the major differences between the 1975 <br />model regulations and the revised model regulations. <br /> <br />Hazard Area Concept vs. Floodway Concept <br /> <br />The 1975 model regulations offered only one concept for <br />dividing the floodplain--the hazard area concept. The revised <br />regulations offer two concepts for dividing the floodplain--the <br />hazard area concept and the floodway concept. The floodway <br />concept has been included in the revised model regulations <br />because the Federal Insurance Administration requires it in its <br />detailed Flood Insurance Studies. The Board has designated many <br />Flood Insurance Studies for development of floodplain management <br />programs by Colorado communities. <br /> <br />The hazard area concept states that 18 inches of depth and <br />velocities of three feet per second constitute a high hazard, and <br />that the portion of the floodplain where those criteria are <br />exceeded is the "high hazard area." The remainder of the flood- <br />plain is the "low hazard area." <br /> <br />The floodway concept, which is used as part of the National <br />Flood Insurance Program, states that if encroachment in the <br />floodplain is allowed, a portion of the floodplain must be <br />reserved to assure that water surface elevations from a 100-year <br />flood would not be increased more than 0.5 foot. That reserved <br />area is called the "floodway" and the remainder of the floodplain <br />is called the "f1oodfringe". <br /> <br />Floodprone Areas <br /> <br />The revised model regulations address the issue of communi- <br />ties that have no 'floodplain hazard data and communities that <br />have only approximate floodplain delineations for some of their <br />stream reaches. In the 1975 model regulations, this issue was <br />not addressed. In the past, approximate floodplain delineations <br />(i.e., areas identified as "floodprone") were not designated by <br />the Board. More recently, however, some Flood Insurance Studies <br />based upon the delineation of floodprone areas have been desig- <br />nated on the condition that detailed floodplain information will <br />be provided on a case-by-case basis when develoment is proposed. <br />The revised model regulations provide that in flood prone areas, <br />detailed information must be provided before a decision about <br />approving or denying a proposed use can be made. <br /> <br />d174 <br />ab <br />