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<br />
<br />minimum, for example, the site plan have to include a
<br />map or description of the existing ,'vatercourses and
<br />"vater bodies, flood,vav boundarv, the 100-vear
<br />floodplain (with elevations), anl natural d;ainage
<br />patterns.
<br />The site-specific considerations described in this
<br />chapter illustrate the complexity of balancing
<br />subdivision development with the goal of minimizing
<br />or preventing flood damage. Developers of floodplain
<br />lands and local planners ,,,,ho revie"v site plans arc
<br />encouraged to use the information to measure hmv a
<br />proposed development meets floodplain protection and
<br />drainage control objectives.
<br />
<br />FINDING A WORKABLE APPROACH:
<br />A DESIGN HIERARCHY
<br />FEMA regulations, procedures, and guidance
<br />provided through r\FlP have long focused on
<br />protecting individual structures from flood risk. This is
<br />typically accomplished by requiring the lmvest floors of
<br />homes to be elevated to or above the base flood level
<br />(BFE). To a certain extent, this approach reflects a beliei
<br />that development in floodplains is unavoidable. Tn
<br />many communities, that may be true.
<br />But after nearly 30 years of experience with NFIP,
<br />thousands of floods, and billions of dollars in property
<br />losses, many communities are nmv focusing less on ho"v
<br />to artificially remove buildings from the floodplain and
<br />instead using methods to steer development out of the
<br />floodplain. Recognizing that communities ,vill be
<br />approaching the issue of floodplain development from
<br />varying points, ,ve offer a hierarchy describing four
<br />options for local government policy to guide subdivi-
<br />sion development in a "vay that best promotes the safety
<br />and ,vell-being of citizens who live in flood hazard
<br />areas, protects property from flood damage and de-
<br />struction, and preserves floodplain functions. (See
<br />Figure 4-1; see also Figure 3-3.)
<br />At the top of the hierarchy is what ,'ve consider to be
<br />the best policy for a community-prohibit ne,v
<br />subdivisions in flood hazard areas. Leading advocates
<br />of environmentally sensitive land development
<br />recommend that site planners and developers foHm\'
<br />this policy by considering the floodplain portion of any
<br />site as undevelopable. In Conservation Design for
<br />Subdivisions (1996), for instance, Randall Arendt sets
<br />forth a four-step process (not to be confused \-vith the
<br />four-level hierarchy recommended here) for designing a
<br />conservation subdivision.
<br />Arendt's four-step conservation design process is
<br />preceded by the "background stage," in which data
<br />about soils, ,vetlands, aquifers, vie,vs, farmlands,
<br />woodlands, slopes, habitats, historic features, and
<br />floodplains are coflected, analyzed, and mapped. Step
<br />one of the design process is identifying all potential
<br />conservation areas that will remain as open space.
<br />According to Arendt:
<br />
<br />As a rule of thumb. . .\vetlands, floodplains, and slopes
<br />. . . take first priority for inclusion in the designated
<br />open space, as they represent highly sensitive
<br />environmental resources that are generally considered
<br />to be unbuildable in a legal sense, in a practical sense, or
<br />for reasons of common sense.
<br />
<br />
<br />Steps hvo, three, and four involve locating potential
<br />house sites, designing street alignments, and dra\ving
<br />the lot lines on portions of the site that "vere identified
<br />in the first step as areas able to accept development
<br />\vithout disruption to environmental processes. The
<br />result of this four-step process is a cluster development
<br />design (aka open space subdivision) that usually
<br />includes the same gross density as a conventional
<br />subdivision design that often ignores critical
<br />environmental features.
<br />The policies behind levels hvo, three, and four of our
<br />hierarchy apply to communities where the community
<br />leaders and citizens have determined that some amount
<br />of development in floodplains is unavoidable. These
<br />policies promote design initiatives that seek to
<br />minimize the number of homes in the floodplain, the
<br />impact oi that development on the floodplain, and the
<br />likelihood of increased flood levels off site due to
<br />development.
<br />The policy option in the second level of our
<br />hierarchy is to plat the subdivision in such a way that
<br />each Tot has a buildable portion on natural high
<br />ground (without fill). Tn such a subdivision,
<br />
<br />1/1 this example, residential townhouses on
<br />the right are constructed on a pier foundation
<br />away from the creek. TIle COlflJlJOIl open spacl'
<br />for the dC'uelopme/zt (in the center of the
<br />pictllre) is ill the floodplllhl.
<br />
<br />floodplain lands \vould be used as back yards or
<br />common open space. This technique \-vorks \ve11 for
<br />small subdivisions in which the backyards are largely
<br />in the floodplain. The minimum buildable area of
<br />each lot that must be outside the floodplain can be
<br />included in subdivision and floodplain ordinances. In
<br />some cases, a community may apply performance
<br />standards rather than strict front- and side-yard
<br />requirements to ensure the best placement of each
<br />structure on each site. Under a performance-based
<br />approach, standards for impervious surface limits,
<br />open space requirements, and minimum buildable
<br />areas "'\Tould be applied rather than an exact number
<br />of feet for the front and side yard.
<br />
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