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<br />. <br /> <br />Memorandum/Issues/Rules <br />September 22. 1987 <br /> <br />Rule 5. Standards for Detailed Information <br /> <br />The topographic base map standards under this rule have <br />been made broad enough to cover a wide range of maps. In <br />particular. the contour internal and scale proposed as a <br />minimum standard for the work maps are much less stringent <br />than the two foot contour internal and scale specified by <br />the Board when we contracted for such work. The proposed <br />standard for map scale has been made low so there will not <br />be a conflict with FEMA guidelines on this issue. <br /> <br />Under Hydrologic Analysis. proposed Rule 5.B.3. Drainage <br />Basin Conditions. is intended to set pOlicy statewide <br />using the concept of calculating flood hydrology on the <br />basis of "foreseeable development" (definition 16). This <br />concept has been used by the UD&FCD for many years and it <br />is considered a prudent approach in rapidly developing <br />areas. The more rapid rate of storm water runoff from <br />impervious surfaces in developing areas has been shown to <br />increase peak flows over natural basin conditions. <br /> <br />. <br /> <br />A potential problem with this approach is that FEMA <br />studies are based on hydrology that is expected only 12 <br />months following completion of the study (commonly <br />mistaken as "existing" basin conditions). The rational <br />for this approach, I am told by FEMA. is that it is unfair <br />to make the present generation pay flood insurance <br />premiums based on a future floodplain. FEMA has accepted <br />UD&FCD hydrology in the past only if the average <br />difference in elevation between fully developed and <br />existing conditions at each cross section is less than 0.5 <br />feet. <br /> <br />Once the rule becomes effective. FEMA should be able to <br />accept hydrology based on foreseeable development because <br />this pOlicy may be regarded as a more stringent <br />requirement. Section 60.1(d) of Title 44. Chapter 1. <br />Subchapter B. Parts 50-77 of the Code of Federal <br />Regulations (CFR), also known as the "National Flood <br />Insurance Program Rules and Regulations." revised by FEMA <br />October 1. 1986. states: <br /> <br />. <br /> <br />"The criteria set forth in this subpart are <br />minimum standards for the adoption of flood <br />plain management regulations by flood-prone. <br />mudslide (i.e. mudflow)-prone and the <br />flood-related erosion-prone communities. Any <br />community may exceed the minimum criteria <br />under this part by adopting more comprehensive <br />flood plain management regulations utilizing <br /> <br />-4- <br />