"REGULAORY” FLOODPLAINS: THE LEGAL FICTION OF FLOOD PROTECT1ON
For land use planning purposes, the regulatory floodplain is usually viewed as all lands within reach of a 100 year flood. The Federal Emergency Management Agency (FEMA) produces floodplain maps, defining what’s in and out of the 100-year (or “regulatory”) floodplain in order to implement the National Flood Insurance Program.
Unfortunately, as Friends of the River flood policy expert Ronald Stork has noted, the regulatory floodplain and the federal insurance program have fostered a planning culture that allows people to be blind to geographic realities.
“We need to have the entire floodplain mapped, not just an arbitrarily defined, 100- year flood zone,” says Stork. “Mapping the entire floodplain would allow people to understand the nature and extent of potential flooding, thus giving them a chance to decide to build, rebuild, buy or not buy.
It’s a theme also found in a 1992 federal floodplain management report: “Because the general populace may not have a complete understanding of the natural physical processes, such as hydrologic cycle and river hydraulics, and of geomorphology, they poorly grasp their vulnerability to flooding and the economic, environmental and social benefits of alternative strategies to avoid or reduce risk.
As Stork and others point out, once lands are defined as “protected” and beyond the reach of the 100-year flood typically through the contruction and operation of dams and levees they are no longer considered in the regulatory floodplain. By this gauge, flood insurance and prudent building techniques (such as elevating structures at least one foot above the base flood level) are no longer required; development is allowed to proceed as if the land had been raised above potential flood waters.
However, in many circumstances, simply because homes are no longer in the regulatory floodplain does not mean they are no longer in danger of being flooded. The much coveted status of being mapped outside of the regulatory floodplain provides the legal fiction that a community or home has complete flood protection. It lulls communities into sense of security because they could be in an area by its geographic location, not its uncertain structural protection that remains at risk from a foreseeable flood event.
Despite this fact, the bureaucratic action of defining the limits of the 100-year floodplain can, ironically, give the green light to local governments and developers to place more people and property in partially protected floodplain areas. Quite simply, it allows floodplain development in what otherwise might remain non-urbanized; areas that could provide critical floodplain storage during major storm events.
A good example of this problem can be found up and down California’s Central Valley where, by 1997, local officials had given their initial approval to a number of development projects that eventually could allow more than 250,000 people to take up residence on potentially vulnerable land.