Admin Order 58-16-01 - Laserfiche WebLink

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change when construction is complete). (FEMA Guide for Ordinance Development, 1978; FEMA Independent Study 9, August 1999.) Definition of watercourse. FEMA does not have a definition of watercourse in its regulations. However, the term does have a commonly understood meaning - the channel itself. FEMA policy has been that a watercourse includes only,the channel and banks of the watercourse, not the adjoining floodplain areas. The term "flood carrying capacity" as used in [b] [7] refers to the flood carrying capacity of the channel (except, possibly, in alluvial fan situations). (FEMA August 12, 1993 Rulemaking Call, page 5; July 30, 1996 FEMA Memorandum in response to FEMA Region V.) Maintain the carrying capacity, application in unnumbered A zones only. The alteration or relocation of a watercourse is development and requires a development permit. The alteration standard only applies in unnumbered A zones, since alterations in zones with elevations and/or floodways are addressed by the [c] [10] or [d] [3] encroachment standards. If the watercourse is being altered or relocated in a zone A area, the requirement has two elements; the community must make whatever arrangements are necessary to assure that: • the altered or relocated watercourse has the same or greater capacity as the original watercourse; and • the capacity of the altered or relocated watercourse must be maintained overtime. (FEMA Memorandum to Region V, July 30, 1996.) Same or greater capacity, level of analysis. Concerning the first part of the requirement, NFIP regulations do not specifically limit or address water surface elevation increases in unnumbered A zones. While some type of analysis is required on the part of the community to determine that the altered or relocated watercourse has the same or greater capacity as the original watercourse, FEMA cannot require the community to conduct an analysis similar to the level of analysis required under [c] [10] or [d] [3]. FEMA can only require an analysis commensurate with the level of data that is provided (except for the detailed analysis for a subdivision or large development under [b] [3]). To assure the flood carrying capacity is not diminished in this situation, a community review should include the following basic items for less developed areas: • Making sure the channel size (watercourse), is as big as the original; • Making sure the roughness coefficient of the channel is maintained; • Making sure the square footage of the cross section is relatively the same; and • Making sure that the same or similar material for the bottom (i.e., sand or gravel) is used. For more developed areas, a more detailed analysis should be conducted. A community does not have to seek recognition from FEMA to change its flood map as a result of an alteration but, if it does, another section of the regulations determines the degree of data FEMA will need (this is Section 65.6 [a] [12]). This regulation basically says that FEMA may request additional data in support of the alteration. 2016 PIDS Manual, Appendix, B-3 B-3-2