FEMA has established minimum floodplain management requirements for communities participating in the NFIP. In addition, communities may want to consider enacting regulations that exceed the minimum federal criteria to further prevent loss of life and property damage, and maintain the beneficial uses of floodplains. Additional regulatory measures can be found in 44 CFR §60.22. A few examples of these measures are discussed below.
Some communities are not comfortable with allowing development in the flood fringe that is defined by floodway analyses that assume encroachment may occur until the water surface elevation increases by up to one foot. A one-foot increase in flood heights will increase the potential for flood damage to flood-prone buildings and affect properties that were otherwise not threatened by the BFE. This is especially true in flat areas where a one-foot increase can extend the floodplain boundary inland a considerable distance.
These communities require floodway mapping and encroachment studies to allow a smaller surcharge, usually 0.5 or 0.1 foot. This results in a wider floodway, but less potential for increased flood losses due to future development.
Setbacks may be used to keep development out of harm’s way by establishing minimum distances that structures must be positioned or “set back” from river channels and coastal shorelines.
Setbacks can be defined by vertical height, horizontal distance, or a combination. While floodplain boundaries are defined by vertical measures, horizontal setbacks also provide protection from flood damage especially in coastal areas where wave effects decrease further inland. For coastal shorelines, setback distances act as buffer zones against beach erosion. In riverine situations, setbacks prevent disruption to the channel banks and protect riparian habitat. Such setbacks are frequently created to serve as isolation distances to protect water quality and stream and wetland resources.
Setbacks from watercourses have been used to minimize the effect of non-point sources of pollution caused by land development activities, timber harvesting, and agricultural activities. Solid waste landfills and on-site sewage disposal systems often are restricted within certain distances of a body of water.
Freeboard is an additional height requirement above the base flood elevation that provides a margin of safety against uncertainties in floodplain modeling, waves smaller than three feet, future upstream development, and flood level increases due to flood fringe development. This reduces the risk of flooding and makes the structure eligible for a lower flood insurance premium rate.
While not required by NFIP standards, communities are encouraged to adopt at least a one-foot freeboard to account for the one-foot rise built into the concept of designating a regulatory floodway and the encroachment requirements where floodways are not identified. One of the obstacles that communities may face in adopting freeboard is cost. However, when constructing a new elevated building, the additional cost of adding one or two feet is usually negligible. Elevating buildings above the base flood elevation also reduces flood insurance costs for current and future owners.
Without a stable foundation, an elevated building can suffer damage from a flood due to lateral movement, uplift, debris impact, erosion, scour, or settling. The NFIP regulations provide performance standards for anchoring new buildings and foundations, and fill placement standards for floodproofed buildings in V zones.
However, the NFIP performance standards do not specify how building foundations are to be constructed. Especially in areas where an engineer’s certificate is not required by NFIP regulations, more specific foundation construction standards would help protect buildings from flood damage. One option is to require that a registered professional engineer or architect certify the adequacy of elevated building foundations and the proper placement, compaction, and protection of fill when it is used in building elevations.
Where the hazard is so severe that a community decides to prohibit or limit certain types of development, a location restriction provision may be appropriate. Some communities prohibit some or all development in parts or all of the floodplain. A common approach is to prohibit particular types of structures in the floodway or in areas exceeding certain flood depths or velocities.
Because this is the most restrictive higher regulatory provision, location restriction language has to be carefully drafted to avoid obstacles. Sometimes, a community can tie transfers of development rights or other benefits to a development that avoids the flood hazard area. These types of situations benefit everyone and reduce the potential for challenging the ordinance.
Prohibiting development makes sense in high hazard areas where people are exposed to a life threatening situation even though buildings could be protected from flood damage. For example, it would be appropriate to prohibit development along a narrow floodplain in a stream valley that is susceptible to flash flooding.
For some activities and facilities, even a slight change of flooding poses too great a threat. These activities and facilities should be given special consideration when formulating regulatory alternatives and floodplain management plans.
There are four kinds of critical facilities:
- Structures or facilities that produce, use, or store highly volatile, flammable, explosive, toxic, and/or water-reactive materials;
- Hospitals, nursing homes, and housing likely to have occupants who may not be sufficiently mobile to avoid injury or death during a flood;
- Police stations, fire stations, vehicle and equipment storage facilities, and emergency operations centers that are needed for flood response activities before, during, and after a flood; and
- Public and private utility facilities which are vital to maintaining or restoring normal services to flooded areas before, during, and after a flood.
Ideally, a critical facility should not be located in a floodplain. Communities often prohibit the development of critical or hazardous facilities in or near the floodway, V zones, or the entire floodplain. While a building may be considered protected from the BFE, a higher flood or an error by the builder or operator could result in a greater risk than the community is willing to accept. If locating a critical facility in a flood hazard is unavoidable, then application of higher levels of protection is a common approach, such as higher freeboard or level of floodproofing.
As part of their land use planning and zoning ordinances, many communities consider which uses and densities are appropriate for flood hazard areas. Some elect to zone the floodplain for agricultural open space or other low-density uses to minimize the number of structures that can be built.
The natural and beneficial functions of floodplains coupled with nature have led communities to promote and guide the less intensive use and development of floodplains. More communities are requiring that important natural attributes such as wetlands, drainage ways, and floodplain areas be set aside as open space as a condition to approving subdivision proposals and large lot commercial developments.
The federal regulation that local permit officials see most often is the program established by Section 404 of the Clean Water Act. Jointly administered by the U.S. Army Corps of Engineers and the U.S. Environmental Protection Agency, the Section 404 program regulates the discharge of fill or dredged material into U.S. waters including adjacent wetlands.
Section 303(b)(1) of the Clean Water Act (1972) provides extensive environmental criteria for judging permit applications while emphasizing the need to prevent avoidable losses of aquatic resources as well as the need to minimize adverse environmental impacts.
The desire to reduce the cumulative impacts of wetland losses has led many jurisdictions to adopt a “no net loss of wetlands” policy. No net loss is addressed either in terms of acreage or the functional value of the wetlands. Despite these programs and other such efforts, as recently as 1989 it was estimated that the country was losing 300,000–450,000 acres of wetlands annually.