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<br />FLOODPLAIN ALTERATIONS
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<br />A. Floodways
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<br />If a community has a regulatory floodway and the local floodplain'
<br />administrator determines that the proposed development is located
<br />within it, then a permit may not be issued unless the applicant can
<br />demonstrate that his development will not increase flood heights at all,
<br />Usually such developments are limited to open,space uses for rec,
<br />reational or agriculture,
<br />Structures existing in a floodway prior to floodway identification are
<br />"grandfathered" in and are not subject to NFIP requirements, Any sub-
<br />stantial improvements (50 percent of the market value or more) to such
<br />structures, however, must be in compliance with the floodplain
<br />ordinance, However, it is permissible for a manufactured (formerly
<br />mobile) home to replace one that has moved out of a preexisting
<br />manufactured home park. The new manufactured home would, however,
<br />have to meet anchoring (tie-down) requirements, FEMA's new provision
<br />on elevating manufactured homes (or substantial improvements) in exist-
<br />ing manufactured home parks on a permanent foundation at or above
<br />the BFE has been suspended until September 30, 1988, while
<br />additional public comment is reviewed, However, new parks or expan'
<br />sions to existing parks must be elevated to or above the 1 DO-year flood
<br />elevation and anchored on a permanent foundation,
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<br />B. Allowable Floodway Uses
<br />The only developments which may be permitted in a flood way are
<br />those which will not cause any increase in the BFE. Typically these
<br />include:
<br />-Agricultural uses not involving structures,
<br />-Uses incidental to industrial or commercial structures such as load-
<br />ing areas, parking areas, and airport ianding strips,
<br />,Private and public recreational uses, such as golf courses, driving
<br />ranges, picnic grounds, boat launching ramps, swimming areas,
<br />wildlife and nature preserves, fish hatcheries, target ranges, hunting
<br />and fishing areas, hiking and horseback,riding trails,
<br />-Uses incidental to residential structures such as lawns, gardens,
<br />parking areas, and play areas,
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<br />C. Watercourse Alterations
<br />Whenever a local floodplain administrator reviews a development
<br />permit that includes a watercourse alteration (for example, realignment
<br />or diversion of a stream, ditch, or river), he must be satisfied that the
<br />flow-carrying capacity of the watercourse will not be diminished, In
<br />order to do this, the permit applicant must supply a thorough descrip'
<br />tion (a set of plans and calculations) of the proposed alteration and its
<br />effect on flows, If the administrator does not have the technical back'
<br />ground to review such descriptions, he must rely on the community's
<br />engineering staff or seek outside professional assistance, Basic items
<br />the administrator should look for include:
<br />'Determination that the hydraulic capacity of the water course will be
<br />the same or greater after the alteration, For example, if a new road
<br />is crossing a stream or creek, culverts under the road must not
<br />place an undue constriction on the channel, causing flood water to
<br />back up,
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