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When the elevation of the lowest grade adjacent to the'structure or the elevation of the lowest portion of a parcel of land is to be deter- mined to be at or above the effective BFE, FEMA will issue a LOMA stating that the effective map has been amended to exclude the struc- ture or parcel of land from the SFHA Otherwise; the LOMA will state that the structure or parcel of land is below the BFE and, therefore, in the SFHA When an effective NFIP map is amended by a LOMA, the amend- ment is effective as the the date or the LOMA Copies of LOMA's that amend an effective map are sent to the affected community and the State Coordinator, A conditional LOMA only comments on the proposed plan and does not amend the effective NFIP map, No copies of Conditional LOMA's are distributed. After January 1, 1986, a fee will be assessed for the review of Conditional LOMA requests, c' F_ Floodway Revisions The floodways shown on NFIP maps are developed as part of detailed FISs and are adopted by communities for use in developing sound floodplain management programs. By restricting development in the f1oodway, a community can preserve the conveyance area necessary for the passage of flood waters and avoid significant increases in flood elevations, After a community has adopted a f1oodway, it may become necessary to change the configuration of the f1oodway. The purpose of this chapter is to discuss FEMA policy con- cerning f100dway revisions and to describe the information that must be submitted to support a request for a f100dway revision, Background Encroachments within the 100-year floodplain can increase BFE's by blocking areas of the floodplain that would otherwise be open to convey flood waters, Therefore, FEMA has established f100dways in an effort to achieve a balance between any benefits gained from floodplain develop- ment and the resulting increases in flood hazard, The f100dway is the channel of a stream and any areas of the 100-year floodplain adjacent to It that must be kept free from encroachment to convey the 100-year flood without increasing the BFE's more than a specified amount. FEMA has set a minimum standard of 1,0 foot for the allowable increase, This increase determines the size of the f1oodway, After the limits of the f100dway have been identified, the community may allow development in the remainder of the 100-year floodplain (the f100dway fringe) with the assurance that flood hazards will not be increased significantly, Several States have adopted requirements that limit the allowable increases to less than the FEMA minimum standard, For States that have adopted more stringent standards by legally enforceable statutes or regulations, FEMA computes f100dways using these standards, Once the f100dway has been adopted by the community, any encroachments within the f100dway that would increase the BFE's during the 100-year flood are prohibited, These encroachments would include fill, new con- struction, substantial improvements, and other types of development. Floodways are developed for streams studied by detail methods as part of the hydraulic analyses performed for these streams, The most common method employed to develop f100dways is referenced to as the "equal conveyance reduction method" in which the hydraulic computer model used to determine the BFE's is modified to eliminate equal amounts of conveyance area from opposite sides of the 1 OO-year flood- plain until the allowable rise in the BFE is reached, When it is necessary to develop f100dways with specific configurations requested by the community, unequal amounts of conveyance area may be used, The resulting f100dway is a reasonable depiction of the area that must be kept open to convey flood waters and is not necessarily the minimum area required to meet the FEMA or State standards, Once adopted by the community, a particular f100dway configuration becomes administratively established, much the same as other community regulations do, and the limits of the floodway are intended to remain unchanged, However, there are generally two situations in which a community may find it necessary to request a floodway revision: . When an Appeal or a Map Revision results in changes to effective BFE's ( ( 32